voorbeeld van - faculty of natural and agricultural sciences
TRANSCRIPT
154
BYLAE 2:
Gevallestudies van grondopnames Bladsy
VOORBEELD 1 155 Detailverkenning grondopname, interpretasie en evaluering van die gronde se geskiktheid vir
verskeie nie-landboukundige gebruike. J.L. Schoeman & T.E. Dohse
VOORBEELD 2 168 Detail grondopname, interpretasie en evaluering van die gronde se geskiktheid vir die verbouing van somer- en wintergrane, en aangeplante weiding. J.L. Schoeman & H.J. Smith
VOORBEELD 3 173 Intensiewe grondopname, interpretasie en evaluering van die gronde se geskiktheid vir landskapdoeleindes. E. Verster & T.H. van Rooyen
VOORBEELD 4 178 Verslag, interpretasie en evaluering van die gronde se geskiktheid vir bosbou, vanaf ’n intensiewe grondopname. Keith Snyman & Associates
VOORBEELD 5 181 Detail grondopname, interpretasie en evaluering van die gronde se geskiktheid vir besproeiingsdoeleindes. E. Verster & T.H.van Rooyen
VOORBEELD 6 193 Detail grondopname, interpretasie en evaluering van gronde met die oog op rehabilitasie van grond wat deur mynbou aktiwiteite versteur is. Loxton, Venn and Associates
VOORBEELD 7 198 Detail grondopname, interpretasie en evaluering van die gronde se geskiktheid vir besproeiing met rioolafval. Loxton, Venn and Associates
VOORBEELD 8 205 Intensiewe grondopname, interpretasie en evaluering van die gronde se geskiktheid vir die verbouing van appels en pere onder besproeiing. F. Ellis
155
BYLAE 2, VOORBEELD 1 Detailverkenning grondopname, interpretasie en evaluering van die gronde se geskiktheid vir verskeie nie-landboukundige gebruike. J.L. Schoeman & T.E. Dohse (Kaart 2 Grondkaart van Bloemfontein word nie ingesluit nie.) DEPARTEMENT VAN LANDBOU-ONTWIKKELING : NAVORSINGSINSTITUUT VIR GROND EN BESPROEIING, PRETORIA. VERKENNINGSGRONDKAART VAN BLOEMFONTEIN GIDSPLANGEBIED op skaal 1:50 000 deur J.L. Schoeman en T.E. Dohse. N.I.G.B. Verslagnommer: GB/A/91/39 N.I.G.B. Kaartnommers: GB/B17246 & GB/B17247 Mei 1991
INHOUDSOPGAWE 1. INLEIDING 1.1 Doel van ondersoek 2. METODES 2.1 Veldprosedure en klassifikasie; 2.2 Laboratoriumprosedures; 2.2.1 Plastisiteitsindeks 2.2.2 Deeltjiegrootteverspreiding 3. OMGEWINGSFAKTORE 3.1 Moedermateriale 4. RESULTATE 4.1 Gronde 4.1.1 Swel-krimp potensiaal 4.2 Interpretasies 4.2.1 Kriteria en norme 4.2.1.1 Paaie en strate 4.2.1.2 Woonhuise 4.2.1.3 Nywerheidsgeboue 4.2.1.4 Rioolpypleidings 4.2.1.5 Rioolafbraakdamme 4.2.1.6 Parke 4.2.1.7 Stortingsterreine 4.2.1.8 Daaglikse bedekking vir stortingsterreine 4.2.1.9 Begraafplase 4.2.2 Geskiktheid van die gronde van die onderskeie kaarteenhede vir stedelike ontwikkeling 5. GEVOLGTREKKINGS Dankbetuiging Verwysings
1. INLEIDING Die stads- en streekbeplanningskonsultfirma wat ’n gidsplan vir Groter Bloemfontein in opdrag van die Stadsraad ondersoek, het die Instituut genader vir grondkundige inligting. Die 1:50 000 skaal grondkaart wat die westelike gedeelte van die gebied dek is beskikbaar en aan die beplanners verskaf, waarna dit gou geblyk het dat ongeïnterpreteerde inligting nie behoorlik aan die doel beantwoord nie. Vervolgens is op ’n werkwyse besluit wat die volgende ingehou het: Eerstens is ’n snel-verkennings grondopname van die dele van die gidsplan uitgevoer waarvoor daar nie voldoende grondkundige inligting bestaan het nie. Grondmonsters is terselfdertyd getrek vir die bepaling van Atterberg-grense. Tweedens is ’n vereenvoudigde grondkaart opgestel wat die bestaande grondkaart van Bloemfontein-wes inkorporeer, en wat die gidsplan in sy geheel dek. Die gronde is ten laaste geïnterpreteer en geëvalueer vir stedelike landgebruike.
Doel van die ondersoek Die doel van die ondersoek was, om op ’n verkenningskaal, voldoende grondkundige inligting vir die gidsplangebied in te samel, dit te interpreteer en aan beplanners wat met die gidsplan betas is, te voorsien, sodat betrokkenes van die volgende bewus gemaak kan word: • die benaderde ligging van die belangrikste grondtipes wat binne die gidsplan voorkom, • pertinente grondverwante probleme wat eie is aan elke belangrike grondtipe, en • die ligging van goeie landbougrond wat, waar prakties moontlik, vir die landbou behoue behoort te bly. Dit moet beklemtoon word dat met die ondersoek slegs beoog is om breë riglyne te trek. Verdere gedetailleerde grondondersoeke sal nodig wees indien besluit sou word om met ontwikkeling in ’n gebied in te beweeg.
2. METODES
2.1 Veldprosedure en klassifikasie ’n Aanvullende grondopname, hoofsaaklik van die oostelike helfte van die gebied (kyk Kaart 2), is gedurende April 1991 uitgevoer deur observasies met ’n handgrondboor op uitgesoekte plekke te doen. Belangrike grondkenmerke is aangeteken, en word as Bylaag I aangeheg. Afkortings wat in die bylaag gebruik word, word in Bylaag 2 verduidelik. Die ligging van observasiepunte word op Kaart 2 aangedui. Monsters van kleierige horisonte wat algemeen voorkom, is met behulp van die grondboor getrek. Die ouer grondopname van Bloemfontein-wes was as ’n M.Sc. studie deur T.E. Dohse in 1971 met behulp van lugfoto's uitgevoer. Die gronde was volgens die destydse proefuitgawes van die Binomiese Sisteem (1977) geklassifiseer. Heelwat standaard grondontledings (wat tekstuur en chemiese ontledings insluit) was gedoen. Die huidige saamgestelde kaart toon die gronde soos geklassifiseer volgens die hersiene uitgawe van die Binomiese Sisteem (Grondklassifikasiewerkgroep, 1991) .
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2.2 Laboratoriumprosedures
2.2.1 Plastisiteitsindeks Die S.A. Standaard Casagrande-bakkie metode vir die bepaling van die vloeigrens is gebruik (Grondklassifikasiewerkgroep, 1991).
2.2.2 Deeltjiegrootteverspreiding ’n Pipet-metode is gevolg (Grondklassifikasiewerkgroep, 1991).
3. OMGEWINGSFAKTORE
3.1 Moedermateriale Volgens die geologiese kaart van die gidsplangebied wat deur Geologiese Opname opgestel is (Geologiese Opname Plan Nr. 1988/0073/0090), word die westelike derde van die gebied deur skalie van die Ecca Groep onderlê. Die oostelike twee-derdes word deur sandsteen, sliksteen en skalie van die Beaufort Groep onderlê. Doleriet kom verspreid, maar veral onmiddellik ten noorde van die stad, voor. Hierdie moedermateriale verweer oorwegend tot betreklike kleierige gronde. ’n Eoliese sandlaag, wat dik (bv. kaarteenheid HuA) of baie dun mag wees (bv. kaarteenheid HuC), kom wydverspreid in die gebied voor. Langs die strome blyk die laag grootliks verwyder of in die grond vermeng te wees (bv. kaarteenhede Sw, Va). Elders gee dit aanleiding tot sanderige solums (bogrond plus boonste ondergrond) wat kleierige, dieper ondergronde onderlê (bv. kaarteenhede Bv en Ss). Vlak gronde (kaarteenhede L en R) kom oorwegend op doleriet voor.
4. RESULTATE
4.1 Gronde Die gronde van die gebied is in elf kaarteenhede ingedeel (kyk Kaart I). Die kaarteenhede word in Tabel I gedefinieer in terme van dominante en subdominante gronde. Die dominante gronde word verder gedefinieer in terme van hul kleur, struktuur, tekstuur, dikte van horisonte en die voorkoms van rots. Die tabel dien ook as legende tot die grondkaart.
Tabel 1 Legende tot die grondkaart KAARTEEN-HEID
GRONDE DOMINANTE GRONDE Grondvorm Grondfamilie
SUBDOMINANTE GRONDE Grondvorm Grondfamilie
BESKRYWING VAN DO- MINANTE GRONDE
HuA Diep, rooi sand Hutton Ventersdorp Plooysburg Rietrivier Geelrooi, struktuurlose, fynsand bogrond, 200-300 mm diep, oor geelrooi, apedale leemfynsand of fynsandleem ondergrond, 1200-1800 mm diep; op plekke onderlê deur hardebank karbonaat.
HuB Diep, rooi leem Hutton Ventersdorp Plooysburg Rietrivier Rooi of donkerrooibruin, struktuurlose leemfynsand of fynsandleem bogrond, 200-300 mm diep, oor rooi of donkerrooi, apedale fynsandleem of fynsandkleileem ondergrond, 1000-1500 mm diep, onderlê deur swak blokkige fynsandklei wat na verweerde doleriet oorgaan, of deur hardebank kalkreet.
HuC Vlak, rooi leem; meestal op doleriet
Hutton Ventersdorp Glenrosa Swartland Mispah
Tsende Rouxville Myhill
Rooi of donkerrooibruin, struktuurlose of swak blokkige fynsandleem of fynsandkleileem bogrond, 200-300 mm diep, oor rooi, apedale of swak blokkige fynsandleem of fynsandkleileem ondergrond, 300-600 mm diep, op betreklik sagte of harde, verweerde doleriet.
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Tabel 1 Vervolg KAARTEEN-HEID
GRONDE DOMINANTE GRONDE Grondvorm Grondfamilie
SUBDOMINANTE GRONDE Grondvorm Grondfamilie
BESKRYWING VAN DO-MINANTE GRONDE
Bv Matig diep rooi leem op prisma-tiese klei; meestal gevlek
Bainsvlei Hutton
Amalia Ventersdorp
Bloemdal Plooysburg Westleigh
Roodeplaat Rietrivier Mareetsane
Rooi of donkerrooibruin, struktuurlose leemfynsand of fynsandleem bogrond, 200-300 mm diep, oor rooi, apedale of swak blokkige fynsandleem of fynsandkleileem, 300-600 mm diep, onderlê deur rooibruin, meestal geel gevlekte, matige of sterk prismatiese sandkleileem of sandklei, 600-900 mm diep, op geelbruin, gevlekte, sterk blokkige sandklei of klei, of sagte kalk onderliggende materiaal.
Ss Vlak bruin leem op prisma-tiese klei
Sterkspruit Smithfield Sterkspruit Bethulie Donkerbruin of donkergeelbruin, swak blokkige of struktuurlose leemfynsand tot sandkleileem bogrond, 50-200 mm diep, wat abrup oorgaan na donkerbruin of donkergeelbruin, sterk prismatiese sandklei, 400-800 mm diep, op geelbruin, gevlekte, sterk blokkige sandklei tot klei, 700-1200 mm diep, oor verweerde sandsteen of skalie met sandkleileem tot klei tekstuur.
Sw Matig diep tot diep bruin klei op sandsteen of skalie
Swartland Amandel Swartland Rouxville Baie donker grysbruin of baie donkerbruin, matig blok fynsandklei of fynsandkleileem bogrond, 100-200 mm diep, op baie donker grysbruin of baie donker bruin, sterk blokkige klei of sandklei ondergrond, 500-1000 mm diep, op grysbruin of geelbruin, sterk of matig blokkige, verweerde sandsteen of skalie, 700-1300 mm diep, met sandklei tekstuur; word onderlê deur betreklik onverweerde rots.
Va Diep Bruin Klei
Valsrivier Mastenhof Valsrivier Serona Baie donker grys of baie donker grysbruin, matig blokkige sandklei bogrond, 100-200 mm diep, op baie donker grys of baie donker grysbruin, sterk blokkige klei ondergrond, 1000-1500 mm diep, oor sterk blokkige sandklei.
Ar Diep donker Swellende klei
Arcadia Rustenburg Baie donker grys, sterk blokkige klei bogrond, 400-800 mm diep, op donker grysbruin, sterk blokkige klei, 1000-1500 mm diep op plekke, op verweerde doleriet; krake en wryfvlakke in bogrond.
Oa Diep Alluviale Leem
Oakleaf Ritchie Bruin, swak blokkige sandkleileem bogrond, 300 mm diep, oor bruin, swak blokkige sandkleileem tot sandklei ondergrond, dieper as 1200 mm; afsettingsgelaagdheid kom voor.
L Vlak klipperige gronde met rotsdagsome
Glenrosa Hutton
Tsende Ventersdorp
Swartland Mispah
Mtini Myhill
Donkerbruin of donkerrooibruin, struktuurlose of swak blok fynsandkleileem of fynsandleem bogrond, 100-300 mm diep, wat direk op verweerde rots (meestal doleriet), of op ’n dun, rooibruin, swak blokkige sandkleileem ondergrond, voorkom; 1 – 20 % blootgestelde rots.
R Rotsdagsome met min of geen grond; steil
Mispah Myhill Glenrosa Swartland
Tsende Mtini
Donkerbruin of donkerrooibruin, swak blok sandkleileem bogrond, 100-200 mm diep, op harde rots (meestal doleriet); 20-70 % blootgestelde rots; hellings van 12-
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50 persent kom oorwegend voor. . . . . . Stroomgebied en
panne
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Tabel 2 Atterberg-grense, liniêre inkrimping, klei-inhoud, aktiwiteit en swelpotensiaal van geselekteerde kleierige horisonte Grondvorm Horison Gemiddelde
diepte (mm) Aantal
monsters Vloeigrens Plas. grens Plas. indeks Liniêre inkrimping Klei-inhoud (%) Aktiwiteit Swel-krimp
Potensiaal Tipe Benaming Gemid
. Bereik Gemid Bereik Gemid
. Bereik Gemid
. Bereik Gemid. Bereik Gemid. Bereik
Arcadia A1
C Vertiese A Ongespesifiseerd
0 - 550 550 - 1200
4 -
61 58-66 15 11-19 46 41-52 13.5 12.6-14.6 56 51-61 0.92 0.84-1.02 hoog/baie hoog
Swartland A1
B1 B2 C
Ortiese A Pedokutaniese B Pedokutaniese B Verweerde rots
0 - 170 170 - 560 560 - 850 850 - 1000
- 5 2 -
53 56
46-64 53-58
19 17
12-26 14-20
34 39
29-38 38-39
8.7 8.0
6.0-12.0 6.3-9.6
49 49
44-56 48-51
0.76 0.87
0.56-0.85 0.83-0.91
hoog hoog
Valsrivier A1
B1 B2 C
Ortiese A Pedokutaniese B Pedokutaniese B Ongekons. mat.
0 - 175 175 - 650 650 - 950
950 - 1300+
- 4 - -
55
49-60
20
15-24
35
32-41
10.0
8.6-12.0
53
45-60
0.77
0.59-0.93
hoog
Sterkspruit A1
B1 B2 C
Ortiese A Prismakutaniese B Prismakutaniese B Ongespesifiseerd
0 - 175 175 - 700 700 - 1100
1100+
- 4 4 -
41 43
35-51 32-54
14 14
12-15 10-16
27 29
21-36 17-38
4.6 6.5
1.6-8.6 2.3-14.6
38 40
31-47 35-50
0.83 0.81
0.72-0.90 0.63-0.97
medium/hoog medium/hoog
Bainsvlei A1
B1 B2 B3
Ortiese A Rooi apedale B Sagte plintiese B Ongespesifiseerd
0 - 250 250 - 550 550 - 900
900+
- - 4 1
40 46
31-45
17 16
14-20
23 30
16-29
6.0 2.6
1.0-9.0
44 53
34-48
0.60 0.63
0.51-0.69
medium/hoog hoog
Hutton A1
B1 B2
Ortiese A Rooi apedale B Ongespesifiseerd
0 - 250 250 - 550
550 - 900+
- - 1
49
17
32
7.0
50
0.71
hoog Westleigh A1
B1 B2
Ortiese A Sagte plintiese B Sagte plintiese B
0 - 200 200 - 600 600 - 1000+
- 2 2
49 44
47-50 39-49
16 16
15-16 14-18
33 28
32-34 25-31
4.5 6.7
3.0-6.0 3.0-10.3
47 47
43-51 45-48
0.78 0.68
0.74-0.82 0.63-0.72
hoog hoog
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Akt
iwite
it
Klei-inhoud (%) Aktiwiteit = PI/Klei-inhoud (%) - 5 ArA1 SsB2 BvB3 SwB1 BvB2 HuB2 VaB1 WeB1 SsB1 WeB2 Figuur 1 Klassifikasiediagram vir swel-krimp potensiaal 4.1.1 Swel-krimp potensiaal Die vermoë van die gronde om uit te swel met benatting, is as een van die belangrikste parameters in die evaluasie van geskiktheid vir stedelike ontwikkeling beskou. Vir die beraming daarvan is Atterberg-grense, liniêre inkrimping en klei-inhoud op 33 monsters, verteenwoordigend van die belangrikste kleierige horisonte, in die laboratoriums van NIGB, bepaal. Volgens die werkwyse van die Grondbewaringsdiens (SCS) van die VSA Departement van Landbou (Schoeman, 1982) is aktiwiteit beraam as: aktiwiteit = PI/(klei-inhoud (%) - 5). Aktiwiteit is vervolgens op ’n diagram van die SCS wat daarvoor gebruik word, teen klei-inhoud gestip (Figuur 1). • Uit Tabel 2 en Figuur 1 blyk dat die swel-krimp potensiaal van die Arcadia gronde (kaarteenheid Ar) hoog tot
baie hoog is. Die liniêre inkrimping is meer as 12. • Die werklike probleemgronde blyk Arcadia, Valsrivier en Swartland te wees (met PI >33; lin. inkr. >8 en klei
aan die oppervlak of baie na aan die oppervlak). • Die ander kleierige horisonte blyk almal tot ’n groter mate deur sand verdun te wees (die klei-inhoud neig
effens laer). Die swel-krimp potensiaal is steeds hoog, behalwe by die Sterkspruit (kaarteenheid Ss) en Bainsvlei gronde (kaarteenheid Bv), waar dit ook in die medium klas val.
• In die geval van die Bainsvlei- en Huttongronde is die kleilaag dieper geleë, maar steeds vlak genoeg dat fondamente direk daarop gelê sal word in meeste gevalle.
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• Kaarteenhede waarvan die gronde nie aan swel-krimp onderhewig is nie, is dus slegs HuA, HuB, HuC en Oa.
4.2 Interpretasies
4.2.1 Kriteria en norme Die kriteria en norme vir verskillende landgebruiksinterpretasies wat met verloop van tyd deur die SCS opgebou is en deur pedoloë van daardie organisasie toegepas word op grondopname-inligting (Schoeman, J.L., 1982; Soil Conservation Service ongedateer), is as vertrekpunt gebruik vir die opstel van onderstaande Tabelle van kriteria en norme. Sommige Tabelle, bv. die oor riool- pypleidings en begraafplase, is tentatief.
4.2.1.1 Paaie en strate (nie snelweë nie) Hier volg die grond- en terreineienskappe wat ’n rol speel in die bou van paaie en strate naamlik die wat betrekking het op die gemak al dan nie van uitgrawing en gelykmaak, en die vermoë om verkeer te dra:
Grondeienskappe Graad van beperking Geen/effens matig ernstig 1. Diepte tot vaste rots of gesementeerde
laag (mm):
hard >1000 500-1000 <500 sag >500 <500
2. Diepte tot watervlak (mm) >750 300-700 0-300 3. Helling (%) 0-8 8-15 >15 4. Oorstromingsgevaar geen:
beskerm selde algemeen
5. Swel-krimp potensiaal (op 250-1000 mm diepte)
laag
matig
hoog
6. >75 mm fraksie (vol. %) <25 25-50 >50
4.2.1.2 Woonhuise (10 - 20 kpa) Konvensionele fondamente wat op ongeveer 600 mm diepte op onversteurde grond rus, word as die norm aanvaar. Grondkenmerke wat in ag geneem word, is die wat sterkte en versakking onder belading beïnvloed, asook swel-krimp potensiaal is:
Grondeienskappe Graad van beperking Geen/effens matig ernstig 1. Oorstromingsgevaar geen selde tot
algemeen 2. Diepte tot watervlak (mm) >750 450-750 0-450 3. Swel-krimp potensiaal laag matig hoog 4. Helling (%) 0-8 8-15 >15 5. Diepte tot vaste rots of gesementeerde laag (mm): hard:
>1000
500-1000
<500 6. >75 mm fraksie (vol. %) <25 25-50 >50 7. Swig gevaar LmSa Sa, LmSa
E-horison Opmerking: Die moontlikheid van swiggevaar moet by aangeduide teksture ondersoek word omdat dit nie doeltreffend deur tekstuur, struktuur of konsistensie voorspel word nie.
4.2.1.3 Nywerheidsgeboue Soos vir woonhuise, maar steil hellings is meer beperkend. Die onderskeidelike hellingsklasse is 0-4%, 4-8% en >8%.
4.2.1.4 Rioolpypleiding Retikulasienetwerke met pype van 150 mm in deursnee en met buigsame voeë word as uitgangspunt geneem.
Grondeienskappe Graad van beperking
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Geen/effens matig ernstig 1. Diepte tot vaste rots of gesementeerde
laag (mm):
hard >2000 1000-2000 <1000 sag >1000 <1000
2. Helling (%) <1 >8 >15 3. Swel-krimp potensiaal laag matig matig
4.2.1.5 Rioolafbraakdamme Die uitgangspunt is vlak damme wat gebou word vir die stoor van rioolafval terwyl die vloeibare en vaste afvalstowwe deur aerobiese bakterie afgebreek word. Die vloer is naastenby gelyk; dit mag versonke wees, of die walle mag opgebou wees uit gekompakteerde grondmateriaal. Die diepte van die rioolafval is gewoonlik 300 tot 1500 mm. Betreklike ondeurdringbare grond vir die vloer en kante is gewens om syfering en besoedeling van die plaaslike grondwater te beperk. Grondkenmerke wat in ag geneem word, is dus die wat betrekking het op deurlatendheid, gemak van konstruksie, besoedeling en die skep van anaërobiese toestande (bv. organiese materiaal in die grond).
Grondeienskappe Graad van beperking Geen/effens matig ernstig 1. Permeabiliteit (mm/u) op 300 tot 1500
mm diepte
<15
15-50
>50 2. Diepte tot vaste rots of gesementeerde
laag (mm) >1500 1000-1500 <100
3. Oorstromingsgevaar geen beskerm
selde algemeen
4. Helling (%) 0-2 2-7 >7 5. Diepte tot watervlak (mm) >1500 1000-1500 0-1000 6. >75 mm fraksie (vol. %) <20 20-35 >35
4.2.1.6 Parke Die gemak waarmee die grond gelyk gemaak en gras, sierstruike en bome gevestig kan word, sowel as die vermoë om voet- en ander verkeer te dra na vestiging van die gras, is faktore wat in ag geneem word.
Grondeienskappe Graad van beperking Geen/effens matig ernstig 1. Soute (mS/m in bogrond) <400 400-800 >800 2. NAV (bogrond) >12 3. Grondreaksie (pH bogrond) >3.6 4. 2-75 mm fraksie (vol. % in bogrond)
<25
25-50
>50
5. >75 mm fraksie (vol. % in bogrond)
<5
5-30
>30
6. Diepte tot watervlak (mm) >600 300-600 0-300 7. Beskikbare waterhouvermoë (mm/mm) >0.1 0.05-0.1 <0.05 8. Oorstromingsgevaar geen
selde beskerm
soms dikwels
9. Helling (%) 0-8 8-15 >15 10. Diepte tot vaste rots of gesementeerde laag (mm):
>1000
500-1000
<500 11. Tekstuur (bogrond) Growwer as
LmcoSa, Sa LmcoSa, Sa SiCl*, Cl*,
SaCl*, coSa 12. Organiese materiaal veen
* As kleimineraal kaolinities is, beskou as een graad minder beperkend.
4.2.1.7 Stortingsterreine (uitgrawingstipe) Dit is terreine wat gebruik word vir die storting van soliede afval. Die afval word daagliks met ’n dun laag grond, wat uit die uitgrawing kom, bedek. Wanneer die uitgrawing vol is, word dit met ’n finale grondlaag van ten minste
162
600 mm dik, oordek. Omdat die uitgrawing so diep as 5 m en meer mag wees, is die grondinligting wat in die loop van ’n grondopname ingesamel word, nie voldoende nie. Geologiese ondersoeke is nodig om die gevaar van besoedeling van die grondwater, asook die beste ontwerp, vas te stel. Grondkenmerke wat in ag geneem word, is die wat betrekking het op natheid, gemak van uitgrawing en die geskiktheid van die uitgegraafde grond as daaglikse bedekking en as groeimedium vir plante.
Grondeienskappe Graad van beperking Geen/effens matig ernstig 1. Oorstromingsgevaar geen
beskerm selde algemeen
Diepte tot vaste rots of gesementeerde laag (mm) <1800 3. Permeabiliteit (mm/h) van dieper lae >50 4. Diepte tot watervlak (mm) sittend grondwater
>1200
600-1200
0-600
0-1800 5. Helling (%) 0-8 8-15 >15 6. Tekstuur* ClLm, SaCl
SiClLm, LmSa SiCl, Cl
Sa 7. >75 mm fraksie (vol. %)** <20 20-35 >35 8. NAV >12 9. Grondreaksie (pH) <3.6 10. Soute (mS/m) >1600 * Dikste laag tussen 250 en 1500 mm. As kleimineraal kaolinities is, slaan een klas beter aan. ** Gemiddeld tot 1500 mm diepte.
4.2.1.8 Daaglikse bedekking vir stortingsterreine Grondeienskappe wat in ag geneem word, is die wat betrekking het op gemak van uitgrawing, herwinbaarheid en toeganklikheid van die leengebied, asook geskiktheid as groeimedium.
Grondeienskappe Graad van beperking Geen/effens matig ernstig 1. Diepte tot vaste rots, gesementeerde laag of ongeskikte materiaal (mm)
>1500
1000-1500
<1000
2. Tekstuur* ClLm,** SiClLm,**
SaCl,** LmSa
SiCl** Cl** Sa
3. Growwe fragmente (vol. %) *** <25 25-50 >50 4. Helling (%) 0-8 8-15 >15 5. Helling (%) 0-8 8-15 >15 6. Grondreaksie (pH) <3.6 7. Soute (mS/m)** >1600 8. NAV >12 * Laat buite rekening in droë gebiede. ** Een graad minder beperkend indien kleimineraal kaolinities is. *** Dikste laag tussen 250 en 1500 mm
4.2.1.9 Begraafplase Grondeienskappe wat in ag geneem word is die wat betrekking het op grondwater, oorstroming, gemak van uitgrawing en swel-krimp.
Grondeienskappe Graad van beperking Geen/effens matig ernstig 1. Oorstromingsgevaar geen,
beskerm selde,
algemeen 2. Diepte tot vaste rots, gesementeerde
163
laag of nie-geskikte materiaal (mm) hard sag
>2000 >2000
>2000
<2000 <1500
3. Diepte tot watervlak (mm) >2500 <2000 4. Konsistensie (nat)* nie-klewerig klewerig baie klewerig 5. >150 mm fraksie (vol. %) <05 5-10 >10 6. Swel-krimp potensiaal laag matig hoog
*Bogrond
4.2.2 Geskiktheid van gronde van die onderskeie kaarteenhede vir stedelike ontwikkeling Met bostaande norme in gedagte, is die geskiktheid van die gronde van die onderskeie kaarteenhede vir stedelike ontwikkeling beraam (kyk Tabel 3). • Tabel 3 toon aan dat die diep, rooi gronde van kaarteenhede HuB en HuA ’n hoë graad van geskiktheid vir die
belangrikste gebruike het. (Dit is egter ook hierdie gronde wat ’n mate van geskiktheid besit vir droëland gewasverbouing).
• ’n Matige graad van geskiktheid word hoofsaaklik by die vlak gronde op rots of klei van kaarteenhede HuC en Bv gevind.
• ’n Lae graad van geskiktheid word hoofsaaklik by die kleierige gronde van kaarteenhede Ss, Sw, Va, Ar gevind, asook by die alluviale gronde wat aan oorstroming onderhewig is, naamlik kaarteenheid Oa, sowel as die klipperige en baie vlak gronde van kaarteenheid L. Die kliprante (kaarteenheid R) is nie geskik nie.
• Die relatiewe geskiktheid vir stedelike ontwikkeling van die onderskeie kaarteenhede kan moontlik soos volg aangedui word: HuA > HuB > Bv > HuC > Ss > Oa > Sw > L > Va > Ar > R.
5. GEVOLGTREKKINGS Die volgende gevolgtrekkings kan uit bostaande resultate en uit die verspreiding van gronde, soos aangetoon op die grondkaart, gemaak word: 1. In breë trekke gesien, besit ’n groot gedeelte van die gidsplangebied (kaarteenhede HuA, HuB en Bv), ’n
matige tot hoë geskiktheid vir stedelike ontwikkeling. Daarvan besit kaarteenheid HuA die hoogste geskiktheid. Geskikte gronde kom kolsgewys rondom die stad voor, maar is duidelik gekonsentreer in die noordwestelike segment van die gidsplangebied.
2. Aansienlike gedeeltes word beslaan deur gronde met ’n oorwegend lae geskiktheid. Die grootste probleem is swellende klei (kaarteenhede Ar, Va, Sw en Ss). Die Arcadia gronde (kaarteenheid Ar) besit ’n hoë tot baie hoë swel-krimppotensiaal. Kleigronde kom veral langs die groter strome en op doleriet voor, en is gekonsentreer in die ooste en noorde.
3. Gedetailleerde grondkundige kartering en grondontledings kan ’n betekenisvolle bydrae maak wanneer daar tot die beplanning van ’n dorpsuitbreiding oorgegaan word.
Dankbetuiging Mev. M.M. Kruger word bedank vir die entoesiastiese en bekwame manier waarop die Atterberg limiete bepaal is.
VERWYSINGS Grondklassifikasiewerkgroep (1991) . Grondklassifikasie. ’n Taksonomiese Sisteem vir Suid-Afrika. Departement
van Landbou-Ontwikkeling. Pretoria. Macvicar, C.N, De Villiers, J.M., Loxton, R.F., Verster, E., Lambrechts, J.J.N., Merryweather, F.R., Le Roux, J.,
Van Rooyen, T.H. & Harmse, H.J.van M., 1 977. Grondklassifikasie. ’n Binomiese Sisteem vir Suid-Afrika. Departement van Landbou-Ontwikkeling. Pretoria.
Schoeman, J.L., 1982. Die interpretasie van grondopnamedata vir landbou en ander doeleindes. Verslag oor buitelandse reis. Ongepubliseerde verslag: Navorsingsinstituut vir Grond en Besproeiing. Pretoria.
Soil Conservation Service. Ongedateer. National Soils Handbook. Op pers. VSA Dept. van Landbou. Washington DC.
165
Tabel 3 Beperkende faktore en die geraamde graad van geskiktheid van dominante gronde van die onderskeie kaarteenhede vir geselekteerde gebruike Paaie en strate Woonhuise Nywerheidsgebou
e Rioolpyplei-dings
Rioolafbraak-damme
Parke Stortingsterreine (Uitgrawingstipe)
Daaglikse bedekking vir stortingsterreine
Begraafplase K
aarte
enhe
id
Bep
erke
nde
fakt
ore
Gra
ad v
an
gesk
ikth
eid
Bep
erke
nde
fakt
ore
Gra
ad v
an
gesk
ikth
eid
Bep
erke
nde
fakt
ore
Gra
ad v
an
gesk
ikth
eid
Bep
erke
nde
fakt
ore
Gra
ad v
an
gesk
ikth
eid
Bep
erke
nde
fakt
ore
Gra
ad v
an
gesk
ikth
eid
Bep
erke
nde
fakt
ore
Gra
ad v
an
gesk
ikth
eid
Bep
erke
nde
fakt
ore
Gra
ad v
an
gesk
ikth
eid
Bep
erke
nde
fakt
ore
Gra
ad v
an
gesk
ikth
eid
Bep
erke
nde
fakt
ore
Gra
ad v
an
gesk
ikth
eid
HuA Moont-lik swig-ting
Hoog Moontlik swigting
Hoog Moontlik swigting
Hoog Geen Hoog Permea-biliteit
Laag Tekstuur Matig Grond-diepte
Hoog tot matig
Tekstuur Hoog tot matig
Grond-diepte
Hoog tot matig
HuB Geen Hoog Geen Hoog Geen Hoog Geen Hoog Permea-biliteit
Laag Geen Hoog Grond-diepte
Hoog tot matig
Geen Hoog Grond-diepte
Hoog
HuC Grond-diepte
Matig tot laag
Grond-diepte
Matig tot laag
Grond-diepte
Matig tot laag
Grond-diepte
Laag Permea-biliteit Grond-diepte
Laag Gronddiepte Hoog tot matig
Grond-diepte
Laag tot geen
Grond-diepte
Laag Grond-diepte
Laag
Bv Geen Hoog Swel-krimp in dieper ondergrond
Matig Swel-krimp in dieper ondergrond
Swel-krimp
Swel-krimp Grond-diepte
Matig Permea-biliteit Grond-diepte
Hoog tot matig
Geen Hoog Grond-diepte
Hoog tot matig
Tekstuur in dieper ondergrond
Matig tot laag
Grond-diepte
Hoog tot matig
Ss Geen Hoog Swel-krimp
Matig Swel-krimp
Matig Swel-krimp
Laag Grond-diepte
Hoog Geen Geen Grond-diepte
Hoog tot matig
Tekstuur Matig tot laag
Grond-diepte
Hoog tot matig
Sw Swel-krimp Grond-diepte
Matig Swel-krimp
Matig tot laag
Swel-krimp
Matig tot laag
Swel-krimp
Laag Grond-diepte
Hoog tot matig
Tekstuur Matig Grond-diepte Teks-tuur
Matig tot laag
Tekstuur Matig tot laag
Grond-diepte Swel-krimp Konsis-tensie
Matig tot laag
Va Swel-krimp
Matig Swel-krimp
Laag Swel-krimp en oorstro-mings-gevaar
Laag Swel-krimp
Laag Oorstro-mings-gevaar
Hoog tot laag
Tekstuur Matig Teks-tuur
Matig Tekstuur Matig tot laag
Oorstro-mings-gevaar Swel-krimp
Laag
Ar Swel-krimp
Laag Swel-krimp
Laag Swel-krimp
Laag Swel-krimp
Laag Grond-diepte
Matig tot laag
Tekstuur Laag Teks-tuur Grond-diepte
Laag Tekstuur Grond-diepte
Laag Grond-diepte Swel-krimp Konsis-tensie
Laag
Oa Oorstro-mings-gevaar
Hoog Oorstro-mings-gevaar
Laag Oorstro-mings-gevaar
Laag Geen Hoog Oorstro-mings-gevaar
Laag Geen Hoog Oorstro-mings-gevaar
Matig Geen Hoog Oorstro-mings-gevaar
Laag
L Grond-diepte Klippe-righeid Helling
Laag Grond-diepte
Laag Grond-diepte Klippe- righeid Helling
Laag Helling Laag Grond-diepte Permea-biliteit
Geen Gronddiepte Klipperig-heid Water-houvermoë
Laag Grond-diepte
Geen Grond-diepte
Geen Grond-diepte
Geen
R Grond-diepte Klippe-
Laag tot geen
Grond-diepte Klippe-
Laag tot geen
Grond-diepte Klippe-
Geen Grond-diepte
Geen Grond-diepte Helling
Geen Gronddiepte Klippe-righeid
Laag Grond-diepte
Geen Grond-diepte
Geen Grond-diepte
Geen
166righeid Helling
righeid Helling
righeid Helling
Water-houvermoë
167
Bylaag 1 Gronddata: Beskrywing van grondobservasies gedoen vir snel-verkenningsopname van gedeeltes van Bloemfontein gidsplangebied: (Vir betekenis van simbole: (kyk Bylaag 2). (Verkort)
Obs. Nr.
Grond- vorm
Familie Tekstuur- klas
Horison Diepte (mm)
Klei (%)
Sand- graad
Kleur Vlek Ed Kalk Struk-tuur
Growwe fragm.
Geo- logie
Opmerkings/ Sak nr.
A1 Ss 1100 fiSaLm A B1 B2 C
20 50 80
100
20 35 35 40
f f f f
10YR33 10YR32 10YR52 10YR52
1y
2 3
m mp mb mb
sa
A2 Es 1100 fiSaLm A E B C
30 70
100 120+
30 10 40 40
f f f f
10YR42 10YR53 10YR42 10YR42
2
m m sp sb
sa
Bylaag 2 Sleutel tot gronddatatabel (Bylaag 1). (Verkort).
GRONDVORM DIEPTE KALK GEOLOGIE Ss = Grondvormafkorting Es
Onderste grens van horison word aangedui
1 = min sa = sandsteen sl = sliksteen
FAMILIE SANDGRAAD 2 = algemeen ms = mikasandsteen 1100 = familiekode f = fyn 3 = volop sk = skalie
TEKSTUURKLAS m = medium STRUKTUUR mo = moddersteen (van A horison vir klassifikasiedoeleindes
c = grof m = massief a = apedaal
OPMERKINGS/ SAKNOMMER
fi = fyn me = medium co = grof Sa = sand Cl = klei
KLEUR Munsell kleure word aangedui
sb = swak blok enige inligting waarvoor daar nie in die voorafgaande kolomme voorsiening gemaak word nie.
HORISON VLEK GROWWE FRAGMENTE
ED
A1 - A2 = A Horison B1 - B3 = B horison
1 = min g = gruis s = klippe
effektiewe diepte van profiel in cm
C = Saproliet/onge- konsolideerde materiaal
2 = algemeen r = rots of rotsblokke 1 = 10 % van horison 2 = 20 % van horison
R = harde rots 3 = 30 % van horison
168
BYLAE 2 VOORBEELD 2 Detail grondopname, interpretasie en evaluering van die gronde se geskiktheid vir die verbouing van somer- en wintergrane, en aangeplante weiding. J.L. Schoeman & H.J. Smith (Die gepaardgaande grondkaarte word nie hier ingesluit nie en die bylaes is verkort.) DEPARTEMENT LANDBOU-ONTWIKKELING: LNR-INSTITUUT VIR GROND, KLIMAAT EN WATER, PRETORIA. GRONDOPNAME VAN DIE PLAAS BELGRAVIA 1023, DISTRIK BETHLEHEM op skaal 1:10 000 deur J.L. Schoeman & H.J. Smith. Augustus 1993
OPSOMMING 1. Die plaas bevat min of meer gelyke oppervlaktes van Avalon-, Westleigh- en Kroonstad-Longlandsgronde
(84 ha, 78ha en 89 ha respektiewelik). Ander gronde (15 ha) sluit in Swartland, Sterkspruit en Glenrosa (figuur 1; Tabel 1; Tabel 4).
2. Effektiewe dieptes wissel soos volg: Avalon, 600-950 mm; Westleigh, 375-425 mm; Kroonstad-Longlands, 525-825 mm; Sterkspruit-Swartland, 200-300 mm en Glenrosa, 250-350 mm (par. 3,1.2,1; Tabel 3).
3. Ernstige chemiese tekorte of wanbalanse kom nie voor nie (par. 3.1.3; Tabel 2). 4. Die bewaringstoestand van die plaas is goed met enkele lande wat beskerming nodig het (par. 3,1.4). 5. Bykans al die lande 1251 ha of 94 %) besit 'n gemiddelde tot hoë geskiktheid vir kontantgewasverbouing
(par. 4; Tabel 4). 6. Al die lande besit 'n gemiddeld tot hoë geskiktheid vir aangeplante weidings (par. 4; Tabel 4). 7. Vir somerseisoen kontantgewasse besit 84 ha (32 %) 'n hoë en 167 ha (63 %) 'n gemiddelde geskiktheid.
Slegs 15 ha (6 %) besit 'n lae geskiktheid (par. 4; Tabel 4). 8. Vir wintergrane besit 173 ha (65 %) 'n hoë en 78 ha (29 %) 'n gemiddelde geskiktheid. Slegs 15 ha (6 %)
besit 'n lae geskiktheid (par. 4; Tabel 4). 9. Waar die geskiktheid laag is, is dit die gevolg van vlak gronddiepte wat aanleiding gee tot die
waterhouvermoë (Bylaag 1; Tabel 3; Tabel 4).
INHOUD OPSOMMING l. INLEIDING EN OPDRAG 2. METODES 2.1 Veldmetodes 2.2 Laboratoriummetodes 3. RESULTATE 3.1 Gronde 3.1.1 Grondkaart 3.1.2 Fisiese kenmerke van die gronde 3.1.2.1 Effektiewe diepte 3.1.2.2 Tekstuur 3.1.3 Chemiese eienskappe van die gronde 3.1.4 Bewaringstoestand 3.2 Geskiktheid van die gronde vir gewasverbouing 4. GEVOLGTREKKINGS 5. VERWYSINGS
1. INLEIDING EN OPDRAG 1.1 Die landerye (266 ha) op die plaas Belgravia 1023, wat in die Bethlehem distrik geleë is, is gedurende
Augustus 1993 grondkundig ondersoek. 1.2 Die doel was om die geskiktheid van die grond vir kontantgewasverbouing te bepaal. Die ondersoek is tot
grond beperk, en sluit dus nie klimaat in nie.
2. METODES
2.1 VELDMETODES 'n Lugfoto van die plaas is vergroot na 1:10 000 skaal om as basiskaart te dien (figuur 1). Met behulp van 'n kompas en deur af te tree, is die grond van die landerye op punte wat 150 m uit mekaar geleë is, ondersoek. By elke observasiepunt is die grond met 'n handboor uitgeboor tot 'n diepte van 1200 mm of totdat 'n grondhorison bereik is wat geag word om buite die effektiewe diepte van die grond vir kontantgewasverbouing te vat. Grondkenmerke wat by elke observasiepunt genoteer is, sluit in tekstuur, kleur, vlekkigheid, struktuur, growwe fragmente en diepte. Die notasies word as Bylaag 1 aangeheg. Die teksture, soos in Tabel 1 en Bylaag 1 aangedui, berus op die vingertoetsmetode in die veld en is nie gekontroleer deur middel van laboratoriumontledings nie. Klein monsters (ongeveer 50 g) van die bogrond is by elke tweede observasiepunt getrek en per kaarteenheid saamgevoeg tot 'n saamgestelde monster. In die laboratoriums van die Instituut vir Grond, Klimaat en Water te Pretoria is die monsters ontleed vir pH (KCI), uitruilbare Ca, Mg, K, Na, ekstraheerbare suurheid en P (Ambic).
169
Die gronde is geklassifiseer in terme van die Taksonomiese Sisteem (Grondklassifikasiewerkgroep, 1991 ). Deur soortgelyke grondobservasies so ver as moontlik saam te groepeer, met inagneming van die lugfotobeeld en helling, is kaarteenhede geskep, gedefinieer en geïnterpreteer in terme van geskiktheid vir droëland kontantgewasverbouing.
2.2 LABORATORIUMMETODES Standaard grondontledingsmetodes, soos beskryf deur die Grondkundevereniging van Suid-Afrika (Soil Science Society of South Africa, 1990) is gebruik.
3. RESULTATE
3.1 DIE GRONDE
3.1.1 Die grondkaart Figuur 1 toon 'n grondkaart van die landerye op 'n skaal van 1:10 000 aan. Die ligging en nommers van observasiepunte word ook aangetoon. Oppervlaktes van die kaarteenhede word in Tabel 4 aangetoon omdat die lugfotobasiskaart nie vir distorsie gekorrigeer is nie, kan oppervlaktes en afstande, soos vanaf die kaart bepaal, 'n mate van fout bevat. Vyf kaarteenhede word onderskei. Die kaarteenhede word in Tabel 1 gedefinieer. Weens 'n aansienlike wisseling in die grondpatroon, bevat sommige kaarteenhede meer as een grondsoort. Die Kroonstad- en Longlandsgronde, asook die Westleigh- en Swartlandgronde kom byvoorbeeld intiem verweef met mekaar voor. Hulle is gevolglik saam gekarteer. Sulke kaarteenhede is gedefinieer in terme van dominante en subdominante gronde. Die geploegde gronde wat die grootste oppervlaktes beslaan, behoort tot die Avalon, Kroonstad en Westleigh vorms. Minder belangrike gronde, wat oppervlakte betref, behoort tot die Longlands-, Swartland-, Sterkspruit- en Glenrosavorm.
3.1.2 Fisiese kenmerke van die gronde Die belangrikste morfologiese kenmerke van die gronde wat ’n rol kan speel in geskiktheid of nie vir gewasverbouing, sluit in kleur, vlekkigheid, tekstuur, struktuur en dikte van horisonte. Hierdie kenmerke word in Tabel 1 aangetoon. Tabel 3 lys 'n aantal grondeienskappe wat nie direk waargeneem kan word nie, maar tog bevredigend van morfologiese kenmerke afgelei kan word. Dit sluit in effektiewe diepte, infiltrasie, interne dreinering, erodeerbaarheid en gevoeligheid vir korsvorming. Effektiewe diepte en tekstuur is van die belangrikste eienskappe wat die waterhouvermoë, en gevolglike geskiktheid al dan nie van grond vir droëlandgewasverbouing, bepaal. Hierdie twee eienskappe word dus hieronder uitgesonder vir bespreking.
3.1.2.1 Effektiewe diepte Tabel 1 toon aan dat die Avalongronde gemiddeld 615 mm diep is tot op die sagte plintiet, en die Westleigh gronde gemiddeld 300 mm. Dit word aanvaar dat ten minste die boonste gedeelte van die sagte plintiese B-horison van daardie gronde 'n bydrae lewer tot effektiewe diepte onder die betrokke klimaatsomstandighede. 'n Arbitrêre diepte van 150 mm is derhalwe tot die horisondiktes, soos in Tabel 1 aangetoon, toegevoeg vir die beraming van effektiewe diepte (kyk Tabel 3). Wat die Kroonstad- en Longlandsgronde betref, is die E-horison (oorwegend geelbruin wanneer klam) in sy geheel beskou as deel van die effektiewe diepte. Die onderliggende G-horison of sagte plintiese B is geag om minimaal (ongeveer 50 mm) by te dra tot die effektiewe diepte van hierdie grondvorms onder die betrokke klimaat. Die kleierige B-horisonte van die Sterkspruit- en Swartlandgronde is eweneens geag om minimaal (ongeveer 50 mm) by te dra tot die effektiewe diepte.
3.1.2.2 Tekstuur Tabel 1 toon aan dat die Kroonstad- en Longlandsgronde, asook die bogronde van die Sterkspruitvorm, 'n sand- of leemsandtekstuur het. Hierdie sanderige teksture gaan gepaard met lae waterhouvermoë en hoë erodeerbaarheid vir wind en water. Die geelbruin apedale horisonte besit oorwegend 'n sandleem of ligte sandkleileemtekstuur. Dit dra by tot 'n gunstige waterhouvermoë. Ondergronde van die Westleigh-, Swartland- en Sterkspruitgronde, asook die dieper ondergronde van die Avalon-, Kroonstad en Longlandsgronde besit ' n sandklei of swaar sandkleileemtekstuur. Tesame met die ongunstige struktuur wat vorm, word wortelontwikkeling in hierdie materiale beperk, waterbeweging is stadig.
170
3.1.3 Chemiese eienskappe van die gronde Resultate van die chemiese ontledings wat gedoen is, word in Tabel 2 aangetoon. Tabel 2 toon aan dat geen ernstige chemiese tekorte of wanbalanse geïdentifiseer is nie. Die fosforstatus van die bogronde is opgebou tot min of meer die optimum vlakke van 18 tot 25 mg/kg wat gestel word (Buys, 1988). Die suurheidsgraad van die bogronde neig na die maksimumvlakke wat nog aanvaarbaar kan wees (pH KCI van 4,5) behalwe in die geval van die Westleighgronde wat die maksimum oorskry. Die kaliumvlakke is aanvaarbaar (hoër as ongeveer 120 mg/kg) behalwe in die geval van die Kroonstad- en Longlandsgronde waar dit aan die lae kant is.
3.1.4 Bewaringstoestand Die bewaringstoestand van die plaas is goed. Slegs in die Sterkspruit-Swartland kaarteenheid, naby die werkershuise, kom noemenswaardige groeferosie in ’n onbeskermde land voor.
3.2 GESKIKTHEID VAN DIE GRONDE VIR GEWASVERBOUING In Tabel 4 word, in die lig van Tabelle 1, 2 en 3, 'n raming gegee van die geskiktheid van die gronde van die vyf kaarteenhede vir die verbouing van somerseisoen kontantgewasse, wintergrane en die tipe aangeplante weidings wat in die gebied van belang is. Die belangrikste beperkende faktore word ook aangedui. Die tabel toon aan dat slegs die Avalongronde 'n hoë geskiktheid het vir somerseisoen kontantgewasse. Vir wintergrane word die Avalon-, Kroonstad- en Longlandsgronde beskou as van 'n hoë geskiktheid. Vir aangeplante weidings word die Avalon- en Westleighgronde beskou as van 'n hoë geskiktheid.
4. GEVOLGTREKKINGS Die volgende gevolgtrekkings word gemaak met betrekking tot geskiktheid van die plaas vir gewasverbouing: 4.1 Bykans al die lande (251 ha of 94 %) besit 'n gemiddeld tot hoë geskiktheid vir kontantgewasverbouing. 4.2 Al die lande besit 'n gemiddeld tot hoë geskiktheid vir aangeplante weidings. 4.3 Vir somerseisoen kontantgewasse besit 84 ha (32 %) 'n hoë en 167 ha (63 %) 'n gemiddelde geskiktheid. Slegs
15 ha (6 %) besit 'n lae geskiktheid. 4.4 Vir wintergrane besit 173 ha (65 %) 'n hoë en 78 ha (29 %) 'n gemiddelde geskiktheid. Slegs 15 ha (6 %) besit
'n lae geskiktheid. 4.5 Waar die geskiktheid laag is, is dit die gevolg van vlak gronddiepte wat aanleiding gee tot lae waterhouvermoë.
5. VERWYSINGS BUYS, A.J. (Red.), 1988. Bemestingshandleiding. Misstofvereniging van S. Afr., Pretoria. GRONDKLASSIFIKASIEWERKGROEP, 1991. Grondklassifikasie. 'n Taksonomiese Sisteem vir Suid-Afrika. Instituut vir Grond, Klimaat en Water, Pretoria. SOIL SCIENCE SOCIETY OF SOUTH AFRICA, 1990. Handbook of Standard soil Testing Methods for Advisory Purposes. GVSA, Pretoria.
171
Tabel 1 Legende tot die grondkaart Kaart- Dominante gronde Subdominante gronde Beskrywing van dominante gronde eenheid Grondvorm Grondfamilie Grondvorm Grondfamilie Av Avalon Mafikeng 3200
Kameelbos 3100 Grysbruin struktuurlose sandleem of ligte sandkleileem bogrond, 300 mm dik, op geelbruin apedale ligte sandkleileem of sandleem,
450-800 mm diep (gemiddeld 615 mm), op gevlekte swaar sandkleileem of sandklei met swak blokstruktuur. We Westleigh Mareetsane 2000 Swartland Gemvale 1121 Grysbruin struktuurlose sandleem of ligte sandkleileem bogrond, 225-375 (gemiddeld 300) mm dik, op gevlekte swaar sandkleileem
of sandklei met swak blokstruktuur. Kd-Lo Kroonstad Grabouw 2000
Morgendal 1000 Longlands Sherbrook 1000
Ermelo 2000 Grysbruin struktuurlose leemsand of sand bogrond, 200-300 mm dik, op grys (of geel-grys wanneer klam) struktuurlose sand, 480-780 (gemiddeld 630) mm diep, op grys, gevlekte sandklei met matige tot sterk prismatiese struktuur.
Ss-Sw Sterkspruit Smithfield 1100 Swartland Gemvale 1121 Grysbruin struktuurlose leemsand of sand bogrond, 200-300 mm dik, op bruin sandklei met sterk prismatiese struktuur. Gs Glenrosa Tsende 1211 Grysbruin leemsand of sandleem bogrond, 200-300 mm dik, op verweerde sandsteen. . . . . . . . Vleiagtige nat kolle 1, 2, 3 ens Grondobservasiepuntnommers Tabel 2 Laboratoriumontledings
Kaart Hor. Diepte pH Uitruilbare katione Uitr. Suur P Eenheid mm (KCl) Na K Ca Mg Tot. Suur Vers. Status cmol(+)/kg grond % mg/kg Av A 0-300 4.5 0.04 0.39 2.40 0.61 3.44 0.47 12 23.8 We A 0-250 4.2 0.08 0.51 3.10 0.54 4.71 1.11 19 19.6 Kd-Lo A 0-250 4.7 0.04 0.24 2.47 1.02 3.29 0.21 6 16.5
Tabel 3 Afgeleide grondeienskappe
Kaart- Grondeienskappe soos afgelei van opname-data Hellingsklas eenheid Effektiewe diepte
(mm) Infiltrasie Interne
Dreinering Waterhou-vermoë Erodeerbaarheid
(water) Erodeer-baarheid (wind)
Natuurlike vrugbaarheid
Gevoeligheid vir korsvorming
Av 600-950 Vinnig Betreklik stadig Matig tot hoog
Matig Matig Matig Hoog 0-3
We 375-425 Matig tot vinnig Betreklik stadig Laag Matig Matig tot laag
Matig Hoog 3-6
Kd-Lo 525-825 Vinnig Stadig Laag tot matig
Hoog Hoog Laag Matig tot hoog 3-6
Ss-Sw 200-300 Matig tot vinnig Betreklik stadig tot stadig
Laag Hoog Hoog tot laag Matig tot laag Matig tot hoog 3-6
Gs 250-350 Matig tot vinnig Matig Laag Matig tot hoog Matig Matig Matig tot hoog 3-6
172
Tabel 4 Beperkende faktore en beraamde graad van geskiktheid vir gewasverbouing Kaart- Opper- Somerseisoen kontantgewasse Wintergrane Aangeplante weiding eenheid
vlak (ha)
Beperkende faktore Graad van geskiktheid
Beperkende faktore Graad van geskiktheid
Beperkende faktore Graad van geskiktheid
Av 84 Min of geen Hoog Min of geen Hoog Min of geen Hoog We 78 Waterhouvermoë Gemiddeld Waterhouvermoë Gemiddeld Waterhouvermoë Hoog Kd-Lo 89 Seisoensnatheid, Erodeerbaarheid,Waterhouvermoë Gemiddeld Min of geen,
Erodeerbaarheid Hoog Seisoensnatheid, Erodeerbaarheid, Waterhouvermoë Gemiddeld
Ss-Sw 10 Waterhouvermoë Erodeerbaarheid
Laag Waterhouvermoë Laag Waterhouvermoë Gemiddeld
Gs 5 Waterhouvermoë Laag Waterhouvermoë Laag Waterhouvermoë Gemiddeld Bylaag 1 Gronddata (Vir betekenis van simbole, kyk Bylaag 2) (Verkort) Obs Nr.
Grond- vorm
Familie
Tekstuur- klas
Horison Diepte (mm)
Klei ( %)
Sand- Graad
Kleur Vlek Kalk Struk- tuur
Growwe Fragm.
Diagnos. Hor.
Effek Diepte (mm)
1 Av 3100 Ap B1 B2
300 550 550+
25 28 36
f f f
m Y M A W co SB
ot ye sp
600
2 Kd 1000 Ap E1 E2 G
250 600 750 750+
20 15 7 36
ff f f f
10YR53 10YR63
f Y c Y c Y mY
M M M M me PR
ot E E G
600
3 Av 3100 Ap B1 B2
350 600 600+
20 24 34
f f f
m YR
M A W co SB
ot ye sp
750
4 We 2000 Ap B
300 600+
25 38
f f
c YR
M W me SB
ot sp
300
173
Bylaag 2 Verduideliking van simbole (Verkort) GRONDVORM Hu = Grondvorm afkorting Es ens.
SANDGRAAD fi = fyn me = medium co = grof
GRO = GROOTTE fi = fyn me = medium co = grof
STRUKTUUR GRA = GRAAD A = apedaal W = swak
GROWWE FRAGMENTE VOORKOMS Die geskatte persentasie van die horison wat beslaan word deur growwe fragmente
GRONDFAMILIE 1100 = Familie kode
VLEKKE VK = VOORKOMS f = min (<2 %) c = algemeen (2-20 %) m = volop (>20 %)
KALK VK = VOORKOMS s = sporadies c = algemeen a = volop
DIAGNOSTIESE HORISONTE oo = Organiese O horison ah = Humiese A horison ve = Vertiese A horison ml = Melaniese A horison
DIEPTE Die onderste grens van ’n horison in mm
MOEDERMATERIAAL UN = Onbekend AL = Alluvium AE = Aeolies
TIPE SG = enkelkorrel MA = massief AB = hoekig blok
TERREINEENHEID 1 = Kruin 2 = Vryhang 3 = Middelhang
FASE Fasenotasies word gebruik waar nodig.
OPMERKINGS Kenmerke waarvoor daar nie voorsiening gemaak is nie, word hier genoteer; bv. oppervlak rots, konsistensie
173
BYLAE 2 VOORBEELD 3 Intensiewe grondopname, interpretasie en evaluering van die gronde se geskiktheid vir landskapdoeleindes. E. Verster & T.H. van Rooyen REPORT OF A SOIL AND LANDFORM SURVEY OF SALVOKOP, PRETORIA by E. Verster & T.H. van Rooyen, 1992. Scale 1:2500 CONTENTS 1. INTRODUCTION 2. METHOD OF SURVEY 3. SOILS AND LANDFORM 3.1 Soil map. 3.2 Short description of the soils and the landform. 3.3 Morphological, analytical and
interpretative soil properties 4. SUITABILITY OF THE SOIL-LANDSCAPE FOR SELECTED LAND USES 1. INTRODUCTION The objective of this survey was to characterise the soil and landform features of the Salvokop area, Pretoria, and to interpret these features in terms of suitability for various landscape planning uses. 2. METHOD OF SURVEY The area, approximately 60 ha in extent, was traversed by vehicle and on foot and the soils, as well as the underlying material, were examined at selected places by means of profile observations. The soils were identified in accordance with the S.A. Soil Taxonomy (Soil Classification Working Group, 1991) and a map legend was compiled. There-after, the distribution of soils was determined by means of augerings and a soil map (scale 1 : 2 500) was compiled. The landforms were noted and described during the soil survey phase and the slope was calculated from the base map. 3. SOILS AND LANDFORM 3.1 Soil map The distribution of the dominant soil forms and families as well as the associated landform is shown on the soil map (figure 1; scale 1 : 2 500). The map legend indicates the variety of soils and provides a brief description of the soils, other surface features and the landform. 3.2 Short description of the soils and land-form The landform comprising a crest (outside the survey area), midslope, footslope and valley bottom (also outside the survey area) is a typical example of slope retreat as a result of incision by the Apies River. The shape of the landform is furthermore controlled by the resistance to weathering and erosion of the quartzite of the Timeball Hill formation. On the southem side of the crest, shale from the same formation occurs in contrast to the shale on the northem side which belongs to the Daspoort formation. The latter is intruded by at least three diabase dykes running from east to west. The dykes are, however, not visible on the surface due to a colluvial covering and it is only in the excavation near the Blue Train shed that deep weathered diabase can be seen. The influence of the diabase on the supply of soil parent material in this area is in any case regarded as being limited. A characteristic of the soils is the colluvium which forms the surface soil and consists of stony, loam to clay loam material. The stones in the colluvium consist in turn of half-rounded gravel and small fragments of the iron-rich quartzite and shale to large quartzite stones and angular boulders. Some of the half-rounded small pebbles are black with a patina appearance which is probably indicative of a different origin and period of deposition and processes. It is interesting to note that the general size of the stones decreases in accordance with the distance travelled from the upper steep mid-slope (map units C and D) to the lower midslope (map unit B), with further decreases in the footslope (map unit A). Although the shale is less resistant to weathering than the quartzite, it has undergone little weathering especially in units A and D where shallow soil overlies only slightly weathered shale. The underlying material in unit B, C and to an extent E, on the other hand, show more and deeper weathering. The saprolite in this case is mostly reddish with a higher clay content and occasionally some structural development. In general, though, the underlying shale has a broken appearance which increases the water permeability slightly and benefits deeper plant roots to a limited extent. As mentioned earlier, the diabase appears to be deeply weathered and consequently is responsible for a slightly higher water seepage capacity of the material in general, whereas the diabase could have contributed to a higher fertility status of the associated soils. An exceptionally thick ferricrete presence is also visible in the excavation near the Blue Train shed and it can be attributed to a former water level that operated in the lower footslope of Salvokop. Apparently, incision by the Apies River disturbed the footslope hydrology so that the ferricrete is today a paleo feature.
174
The following diagram is a summary of the dominant soilscape features: Dominant Soil
form and family Description of soil Associated
landform Glenrosa form Tsende family
Mainly shallow greyish brown structureless stony loam to clay overlying slightly weathered hard shale; parent material consisting of quartzite and shale colluvium on saprolitic shale
Midslope and footslope
Glenrosa form Dumisa family
Greyish brown to reddish structureless stony clay loam overlying moderately weathered soft shale and in places diabase; parent material consisting of quartzite and shale colluvium on saprolitic shale and diabase
Midslope
Clovelly form Leiden family
Mainly shallow greyish brown structureless stony clay overlaying mesotrophic yellow-brown apedal caly merging into shale saprolite with depth; soil has luvic properties; parent material consisting of shale colluvium on saprolitic shale
Midslope
Swartland form Shangoni family
Moderately deep greyish brown to reddish structureless stony clay loam overlying reddish fine structured clay merging into shale and diabase saprolite with depth; parent material consisting of quartzite and shale colluvium on saprolitic sahle and diabase
Midslope
3.3 Morphological, analytical and interpretative soil properties Profile descriptions and analytical data of selected soil profiles are given in table I, while other features, mainly of an interpretative nature, are contained in table 2. 4. SUITABILITY OF THE SOIL-LANDSCAPE FOR SELECTED LAND USES The most important limitations of each map unit, based on the soil and landform factors, are shown in table 3. In table 4 the map units are evaluated in terms of their suitability for the various land uses. Table 1 Morphological, physical and chemical properties of selected soils Observation no. S1 S4 S6 S9 S10 S10 Depth (cm) 0-30 0-20 40-60 20-30 10-30 60-70 Diagnostic horizon Orthic A Orthic A Litocutanic
B Lito-cutanic B
Orthic A Litocutanic B
Colour 10YR2/2 Very dark brown
10YR4/3 Brown to dark brown
2.5YR3/6 Dark red
10R4/6 Red
2.5YR3/4 Dark red brown
2.5YR4/6 Red
Structure Weak blocky
Weak blocky
Apedal Apedal Weak blocky
Apedal
Consistence Hard Hard Slightly hard Hard Hard Hard Material coarser than 2 mm (%)
22.5 gravel and stones
20.6 gravel and stones
76.8 stones
24.7 gravel
49.2 gravel and stones
79.5 gravel and stones
Textural class Sandy loam Clay Clay Clay Clay loam Clay Clay (%) 14 43 49 46 36 56 Silt (%) 14 23 20 17 16 19 Sand (%) 72 34 31 37 48 25 Exchangeable cations (mg/kg) Na
5
4
6
13
4
-
K 482 212 38 322 118 - Ca 2505 777 507 1036 658 - Mg 346 130 148 323 139 - P (mg/kg) 208 8 13 2 24 - pHw 7.4 5.4 5.4 7.2 5.3 4.7 Electr. cond. (mS/m) 42 13 25 78 18 21 Table 2 Interpretative properties of the dominant soils Map symbol Properties
A B C D E
Soil texture - topsoil - subsoil/saprolite
Loam to clay Clay
Clay loam Clay
Clay loam Clay
Clay Clay
Clay loam Clay
175
Stoniness of topsoil (volume %) 20-40 40-70 50-80 20-50 60-90 Depth to weathered rock (cm) 20-50 30-90 30-120 20-40 10-40 Permeability of soil Rapid Rapid Rapid Rapid Rapid Permeability of weathered rock/saprolite
Slow Mod/Slow Mod/Slow Sow Mod/Slow
Drainage class of soil Mod well Well Well Somewhat poorly
Well
High water tabel and duration None None None Very temporary
None
Estimated plant available water (mm/cm)
0.6 0.5 0.5 0.6 0.4
General fertility status Low Moderate Moderate Low Moderate pH class (topsoil) 5.5-7.5 5.0-6.5 5.0-6.5 5.0-6.5 5.0-6.5 Ca + Mg status Medium Medium Medium Medium Medium K status Medium Medium Medium Medium Medium P status Low-high Low Low Low Low Possible trace element deficiency
Moderate Moderate Moderate Moderate Moderate
Salinity None None None None None Erosion hazard - water - wind
Low Low
Low Low
Low/mod Low
Low/mod Low
Low/mod Low
Swell-shrink potential: topsoil subsoil/saprolite
Low Low
Low Low/mod
Low Low/mod
Low Low
Low Low
Compaction of topsoil Low Low Low Low Low Stability of soil High High High High High Water seepage capacity of subsoil/saprolite
Low Low/mod Low/mod low Low/mod
Table 3 Limitations of map units influencing the suitability for selected land uses Map symbol Dominant limitations A Very restricted soil depth; stony topsoil; low inherent soil fertility; slowly permeable
saprolite B Restricted soil depth; very stony topsoil,slightly steep slope C Restricted soil depth; very stony topsoil; moderate steep slope D Very restricted soil depth; stony topsoil; moderate steep slope; low inherent soil fertility;
slowly permeable saprolite E Very restricted soil depth; very stony topsoil; very steep slope; rock outcrops Map symbol Dominant limitations Fa No naturally occurring soil; excavations concrete and building wastes Fb Uneven terrain; large soil dumps Table 4 Suitability of map units for selected uses Map symbol Uses
A B C D E Fa Fb
Dams - pond reservoir area - embankments
3 3
3 3
4 3/4
4 3
4 4
3 4
3 2
Shallow excavations 3 2/3 3 3 4 3 2/3 Foundations for low buildings 2 2 3 3 3 3 2 Local roads and streets 2 2 3 3 3/4 2 2 Landscaping 2 2 3 3 3 3 2 Table 4 Continue Map symbol Uses
A B C D E Fa Fb
Growth medium: -shallow root - deep root
2 3
3 2
3 2
3 3
3 3/2
3 3
2 2
176
Topsoil 4 4 4 4 4 4 4 Camping and picnic terrain 2 2 3 3 4 2 3 Playground 2 3 4 4 4 2 3 Hiking and horse trails 2 2 2/3 2/3 3 2 2 Construction materials - roadfill - sand source - gravel source
4 4 4
4/3 4 4
4 4 4
4 4 4
4 4 4
4 4 4
2/3 4 4/3
Suitability rating: 1 = high 2 = moderate 3 = low 4 = very low to not suitable Legend to Figure 1 Map of the soils and landforms of Salvokop
Map symbol Dominant soils Short description of the soils and surface features
Land form and slope (%)
A
Glenrosa form Tsende family
Shallow (20-50 cm) grey brown, stony loam to clay on weathered shale
Higher footslope 1-4
B
Glenrosa form Dumisa family, Swartland form Shangoni family
Moderate deep (30-90 cm) red stony clay loam on moderate-ly weathered red shale, deep weathered diabase and red structured clay grading to saprolite with depth.
Lower midslope 6-15
C As in B As in B but with few rock outcrops (<10%)
Higher midslope 20-30
D
Glenrosa form Tsende family, Clovelly form Leiden family
Shallow (20-40 cm) grey brown stony clay on yellow mottled slightly weathered shale and yellow apedal clayey soil grading to saprolite with depth; few rock outcrops (<5%)
Midslope 15-30
E
Glenrosa form/ litosols
Many shallow (10-40 cm) and stony clay loam soils on moderately weathered shale with quartzite outcrops (10-30%)
Midslope 25-50
Fa Disturbed terrain with no natural soils occurring (quarry, concrete and building rubbish, etc.) Disturbed footslope – level Fb Disturbed terrain (big piles of soil and saprolitic materials) Disturbed footslope – uneven S10 Observation with soil analysis Deleted: Page Break
¶¶¶
180
h
BYLAE 2 VOORBEELD 4 Vervolg
Plantation General soil discription Land Fertilization Species Limitations Afforest.land prep. (per tree) selection to potentialunit afforest. & expect. y.
Ak216 Brown to dark brown, apedal, fine sandy clay Mechan- 100 g E. grandis High(a-i) loam topsoils 30-50cm thick on red, apedal, ical ammonia- E. dunnii >20 t/ha48.30ha fine sandy clay loam to sandy clay subsoils pit ted supers /yr 8yrs
>150cm deep. (10.5% P)Ak218 Brown to dark brown, apedal, fine sandy clay Rip 100g ammo-E. grandis Restricted High to (a-b) loam topsoils 30-50cm thick on red, apedal, 100 cm niated E. dunnii rooting moderate3.10ha fine sandy clay loam to sandy clay subsoils supers depth 17 - 20
to sandy clay subsoils 60-90 cm deep on (10.5% P) t/ha/yr gravelly saprolite. 8 years
A1201 Brown to dark brown, apedal, fine sandy clay Hand pit 200g P.patula Shallow Moderate(a-p) apedal, fine sandy clay thick on yellow brown 2:3:2(22) P.greggii rooting 11 m3/ha/yr76.00ha or yellow and red, apedal, fine sandy clay loam depth 15 yrs
to sandy clay subsoils 30- 60 cm deep on hard outcropsrock 60% outcrops.
An80 Brown to dark reddish brown, fine sandy clay Hand pit 200g P.elliottii Shallow Low(a-d) loam topsoils 20-40cm thick on hard rock up 2:3:2(22) rooting 8m3/ha/yr 13.50ha to 10% surface rock. depth 15 yrs
Bb20 Dark to dark brown, apedal, fine sandy clay Plough 140g P.elliottii Shallow Low(a) laom topsoils 20-40cm thick on yellow, fine and 2:3:2 -30 rooting <8m3/ha/yr1.00ha sandy clay loam, apedal subsoils 40-60 cm ridge depth, 15 yrs
on unconsolidated material wetnesswith signs of wetness.
Ca100 Brown, massive, clayey, wet topsoils 30 cm Conserva- Exessive Unsuitable(a) thick on massive, clayey mottled grey hydro- tion profile10.00ha morphic material 500cm deep; wetness hazard wetness
flooding.Dd15 Brown pale, clay loam, weak blocky topsoils Rip 350g P. elliottii Shallow Low(a) 20cm thick on brown, strong blocky, clayey 80 cm Agrofert rooting dept (8 m3/ha/yr 25.20ha subsoils 70cm deep on clayey, massive profile 15 yrs)
saprolite; hardsetting. structureEc26 (a) Dark, massive, clayey topsoils more than Conserva- Shrink- Unsuitable15.00 ha 150cm deep; large shrink-swell potensial tion swellFb114 Brown weak blocky, Rip 350g Agro- E.macart- Restricted Moderate (a-b) fine sandy clay loam, 80 cm fert hurrii rooting to low35.00ha gravelly topsoils 20cm depth, 12 t/ha/yr
thick on mottled brown, profile 7 yrsweak blocky, rocky gravelsuboils 70cm deep onmassive, soft saprolitemore than 110cm deep.
Id1 (a) Ja1 Loading zone/excessive compaction UnsuitableJa1 Dark, loamy, massive Conserva- Excessive Unsuitable(a) topsoils more than tion profile 19.50ha 150cm deep; wetness wetness,
bazard; ground fires. ground firesFormat: Forest Soils Database Co-operative: Soil survey standards for consultants, Version 1.2, September 1995, c/o Mondi Forests.
180
r
.
r
181BYLAE 2 VOORBEELD 5 Detail grondopname, interpretasie en evaluering van die gronde se geskiktheid vir besproeiingsdoeleindes. E. Verster & T.H. van Rooyen (Uittreksel uit die oorspronklike verslag) REPORT ON THE DETAILED SOIL SURVEY OF AN AREA ALONG THE OLIFANTS RIVER FROM ARABIE DAM TO APEL, LEBOWA by E. Verster & T.H.van Rooyen, 1991. CONTENT 1. INTRODUCTION 2. WATER QUALITY OF THE ARABIE DAM 2.1 Procedure 2.2 Results and discussion 3. SOILS 3.1 Procedure 3.2 Description of the dominant soils 3.2.1 Textural properties of the soil 3.2.2
Chemical properties of the soils 3.2.3 Soil fertility 3.2.4 Drainability of the soils 4. SUITABILITY OF SOILS FOR IRRIGATION 5. RESULTS 5.1 Extent of irrigable classes 5.2 Suitability of the soils of the Tooseng area for citrus REFERENCES Table 1 Water analysis of the Arabie Dam Table 2 Interpretation of water quality for irrigation Table 3 Morphological properties and analytical data of selected soils Table 4 Selective properties and some interpretative features of the dominant soil units Table 5 Drainability of selected soil units Table 6 Irrigation suitability, recommendations and precautionary measures pertaining to map units CONCLUSIONS AND RECOMMENDATIONS 1.1 After a detail soil survey the area was divided into relative physical irrigation suitability classes. These classes and soil units are shown on the accompanying map (scale 1: 5 000). Of these classes, ratings 1 and 2 can be recommended for irrigation with the necessary preconditions as stated in Table 6. Rating 3 is normally not recommended for large-scale irrigation development under the average conditions pertaining to this study, but small areas may be considered if they adjoin or are enclosed by areas of classes 1 and 2. The irrigation use of class 3 must obviously be subjected to the necessary precautionary measures as stated in Table 6. 1.2 The extent of the different classes available for irrigation per geographical area is summarised in 5.1. From this section, it is also evident that relatively large portions of the existing irrigated areas belong to class 3. It is suggested that the inclusion of this class of land into future irrigation blocks be reconsidered, especially in the light of the scarcity of water, economic factors and the possible degradation of the soil resource. 1.3 Whereas 1.1 refers to a generalised irrigable classification, the suitability of the soils of the Tooseng area were also assessed for citrus production (see 5.2 and Table 6). Of this assessment, classes 1 and 2 can be recommended for citrus. These two classes cover a gross area of about 1 170 ha with a possible extension above the 820 m contour on both sides of the dirt road, north of Tooseng. 2.1 The soil map is a permanent record of the soil types present and a statement of the conditions of the soil resource at the time of survey. It is proposed that all future planning of the scheme must be based on these mapped soil classes. Indeed, soil series must be the basis, among others, for cropping and fertiliser programmes; water application rates and irrigation methods; preparation of lands and tillage of soils; and agricultural gypsum and drainage requirements. 2.2 Although the general soil pattern seems to be simple and predictable, the irrigation suitability of some of the map units, because of the phase differentiation, varies considerably in certain areas. This variability in proposed land use pattern has to be taken into consideration during detail irrigation planning. 3.1 Attention has to be given to the improvement of the fertility status of the soils, especially to nitrogen and phosphate fertilisation. 3.2 As most of the soils tend to form a surface crust and/or may be subjected to compaction, the resultant negative effects on water infiltration, seed-bed preparation, emergence of seedlings, root development and water movement, would require the application of amendments such as agricultural gypsum. 4.1 The installation of subsurface drainage or, at least, the provision for discharge points if infield drainage should become necessary in future, are recommended for certain soils of class 3 (see Table 6) if, however, considered for irrigation. The same recommendation will apply to similar soils already included in the existing irrigation scheme. 4.2 The drainability of selected soils is described in Table 5. Although the drainability differs from soil to soil with resultant differing installation costs, it is clear from Table 5 that all the relevant soil units can readily be drained. 4.3 If a large irrigation development is envisaged such as at Tooseng or on the farm Strydkraal, provision should be made during the planning stage for interceptor drains at regular intervals to collect excess subsurface water.
1825. High water tables and the accumulation of salts in soils should not be tolerated on this scheme. It is therefore recommended that potential problem areas be regularly monitored and should these situations develop, preventative actions such as drainage, improving irrigation system efficiency, application of chemical amendments (gypsum), etc, be taken. 6. The present water quality of the Arabie Dam can be recommended for any relevant irrigation. It is suggested, however, that the water quality is monitored in future to detect any deterioration in quality, especially with respect to the chloride content. 7. Conservation measures to protect the soils against erosion are strongly recommended. 8.1 The clearing of trees and bush and the associated land preparation costs have not been taken into consideration for the assessment of irrigation suitability. These costs are expected to be high in certain parts of the potential areas where dense bush occurs. 8.2 The areas supporting the riverine forests along the banks of the Olifants River are mainly composed of the soils of the Dundee form. It is recommended that these forests be protected and no development be allowed to take place in these areas. 1. INTRODUCTION It is a generally accepted fact that a detail soil survey is a prerequisite for irrigation planning and layout. From the results of the detail reconnaissance soil survey conducted by Verster & Van Rooyen, (1987), areas were selected for the detail survey. These areas, as depicted on maps 8902.3,I and 8902.3.2 of Eksteen, Van der Walt & Nissen, comprise (i) Arabie Dam to Goedverwacht on the right bank of the Olifants River consisting exclusively of existing irrigated lands; (ii) Van der Merwes Kraal to Adriaansdraai on the left bank with existing lands on the farms Grootklip and Adriaansdraai as well as some undeveloped areas; (iii) Veeplaats complex on the right bank consisting of existing lands above the channel on the farms Goedverwacht and Veeplaats as well as a small undeveloped area on the farm Veeplaats; (iv) Tooseng area on the left bank composed of a continuous undeveloped area; and (vi) Wonderboom to Apel on the right bank with existing lands below and above the channel as well as undeveloped areas above the channel on the farms Wonderboom, Vlakplaats and Strydkraal. In total, the proposed survey area comprises a tract of land in excess of 6 250 ha. The main objectives were to characterise and map the soils on a detail level, and to interpret them in terms of irrigation suitability. The latter includes an additional assessment of the irrigation suitability of the soils of the Tooseng area for citrus production. Those properties limiting the suitability of the soils and the precautionary measures normally recommended for sustained irrigation use, will also be given. In addition, the water quality of the Arabie Dam will be assessed. 2. WATER QUALITY OF THE ARABIE DAM Water quality denotes "suitability" for a specific use. For irrigation, water suitability is related to its effect on soils and crops and on the management that may be necessary to control or compensate for a water quality related problem. 2.1 Procedure A single water sample was taken from the Arabie Dam during September 1990 and analysed in the Outspan Laboratories, Verwoerdburg. 2.2 Results and discussion The analysis and an evaluation of the suitability of the water for irrigation are summarised in tables 1 and 2 respectively. From the analysis it is evident that the water has a low salt and boron content, a low sodium adsorption ration (SAR) value and a pHc parameter with no apparent adverse effect on soils. Although one can assume some variability in water quality of the Arabie Dam over a period of a year, the sample was taken after the winter season and may therefore theoretically represent the period in which the water quality will tend to be at its lowest value due to the concentration of solutes resulting from a low flow situation. In general, the water therefore seems suitable for any relevant irrigation development. However, two water quality related problems are expected to develop in future. Firstly, when soils are irrigated with a low salt content water, they are inclined to behave like sodium soils even at relatively low exchangeable sodium percentage (ESP) values. This can lead to a surface crust with a very hard consistence when dry and poor water infiltration. Concomitant with the fact that some of the proposed irrigable soils of this project have an inherent tendency to crust formation (see Table 6), it will be essential to monitor these soils. If these adverse conditions do develop, the application of chemical amendments such as agricultural gypsum is recommended. secondly, with the expected deterioration in the future water quality of the Arabie Dam it is recommended that the chloride content is specifically monitored on a regular basis to ascertain any increase in concentration above the critical value of 3 me/l. (At present the value is 2,68 me/l- Table 1 .) Above this value sensitive crops, if irrigated with such a water, tend to show growth damage and a decrease in quality.
1833. SOILS A relatively simple and predictable soil pattern, associated with specific sites and parent materials, is a feature of this landscape. 3.1 Procedure By means of a grid system, the areas earmarked for the detail study were systematically traversed using a soil auger. soil properties important for assessing the soil's irrigation suitability were noted. Approximately 2100 observations covering an area of about 6 250 ha were made. Orthophoto maps (scale 1 : 5 000) were used in the field to plot all the observations, soil boundaries and other relevant data (see Figure 4.2). Additional soil profiles (36 in total) were described and sampled and the samples analysed in the Outspan Laboratories, Verwoerdburg. The other nine profiles and their analytical results were previously reported by Verster & Van Rooyen (1987) and included here for the sake of completeness. From all the above information, a final soil legend was constructed. The various soil map units were, in turn, assessed for irrigation suitability, measured by planimeter to attain the gross area and drawn on the base maps (scale 1: 5000) accompanying this report. 3.2 Description of the dominant soils Most of the soils, which occupy the project landscape, have been identified during the detail reconnaissance soil survey (Verster & Van Rooyen 1987). A limited number of additional soil series have been identified subsequently. It is important to note that the soils cover the landscape in closely associated units and are composed of various phases (depth, gravely, stony, erosion, wetness, saline and slope) (see soil map and legend). Morphological properties and analytical data of selected soil series are given in Table 3. 3.2.1 Textural properties of the soils The textural properties of selected soil series are shown in Table 3, but are summarised in Table 4 for the dominant soil units. A feature of the soils occurring on the Olifants and Gompies river terraces is the high fine sand content which can contribute to the development of crusting and compaction problems in the area. The sand fraction of the Hutton and Clovelly form soils, which have been derived from granite and magnetite gabbro parent materials, is coarse throughout. In certain granitic areas, however, some of these soils even contain a large gravel fraction (by definition more than 20% gravel in the soil mass) . Because the large gravel content will limit the water bolding capacity and be conducive to the abrasion of implements, these soils have been mapped as a gravel phase. On the other hand, high clay contents of especially the soils of the Valsrivier form are responsible for the heavy draught requirement due to the hard soil consistence and puddling of the surface. All the above conditions will make the application of the correct tillage practices essential. 3.2.2 Chemical properties of the soils The chemical data are contained in Table 3, whereas the average pH class of the dominant soil units is summarised in Table 4. Except for map unit bVBl and to a lesser extent map unit Val (see profile 43) on the farm Mooiplaats, no harmful increase of salts has been recorded in either the irrigated or the undeveloped areas. However, the development of salinity and sodicity problems cannot be entirely excluded in future, especially with a potential source of salts available in the parent materials, water tables tending to develop due to over-irrigation, low-lying soils with subsoil wetness sometimes included into irrigated lands and the expected deterioration in water quality (see 2). The increase in salts (EC value) in the subsoil of profile 28 (Table 3) on the farm Veeplaats may be a preview of this potential problem. 3.2.3 Soil fertility The fertility status of the soils can be inferred from the chemical properties and other data given in Table 3. For a general assessment of the fertility status see Table 4. It is not the objective of this survey to consider fertiliser recommendations because specific recommendations will obviously depend on the type of crop. The following remarks must be seen as relevant only to the improvement of the fertility status of the soils in general. (i) Nitrogen: Although not analysed for, the nitrogen content of the soils especially those of the Hutton and Clovelly forms is low as is to be expected in this climatic region. As most crops require adequate levels of nitrogen to ensure optimum growth, nitrogen fertilisation will be essential. (ii) Phosphorus: The P content is low in the virgin soils and varies from low to high in the irrigated lands, the latter significant variation can be ascribed to previous applications. In addition, with possible availability and fixation problems in especially the Hutton and Clovelly form soils, adequate phosphate fertilisation will be necessary. (iii) Potassium: The soils of the project area appear to have a high K status throughout. Potassium fertilisation must therefore be adapted to these rather high K levels. (iv) Calcium: The Ca content varies from low to medium in the virgin soils of the Portsmouth, Shorrocks, Denhere and Blinkklip series, and is high for the Shigalo and Dudfield series as well as the soils of the Oakleaf, Valsrivier and Dundee forms. (vi) Magnesium: The Mg content varies from medium to high in all the soils. (vii) Micro elements: No particular micro element deficiency can be predicted from the available chemical data. 3.2.4 Drainability of the soils According to the concept of conservation land use, irrigable land must be drainable land. Consequently adequate drainage (surface and subsurface) or the provision for discharged points if infield drainage should become necessary in future, is an integral part of any irrigation scheme. High water tables must not be tolerated in irrigated lands. Therefore soils showing signs of wetness in the virgin state are expected to develop high water tables if irrigated.
184Excess water may also accumulate temporarily in subsoil due to over-irrigation especially in shallow soils as is the case on the farm Veeplaats. In addition, water also tends to accumulate more permanently in low-lyingareas, e-g- map units VBl and wDu4 on the Olifants river terrace. During the survey several map units were demarcated with subsoil wetness and one with a high water Table (see the soil map and legend). To comply with the concept of conservation land use especially over the long-term, these areas, if considered for irrigation development, will require subsoil drainage. The same recommendation will apply to similar soils which are already included in the existing irrigation blocks. An assessment of the drainability of the relevant soils which depends, among others, on depth, permeability of the deep subsoil or material and flooding, is depicted in Table 5. 4. SUITABILITY OF SOILS FOR IRRIGATION Irrigation suitability in this study is based on the soil, landform (site and slope) and water quality factors. Because of these physical determinants, a so-called physical suitability classification is constructed. The different classes and general recommendations are as follows:
Irrigation Suitability
class
General recommendations with regard to sustained irrigation use under the average conditions pertaining to this study
1 Highest physical rating; soils possess properties with none to slight limitations; highly recommended; few preconditions necessary
2 Moderate physical ratings; soils with moderate limitations; recommended with definite preconditions
3 Low physical rating; soil with moderately severe limitations; normally not recommended for large-scale development; however, small area can be included subject to the necessary preconditions
4 Special rating; not encountered in this study 5 Soils with severe limitations; not recommended
Geographical area Gross area of classes (ha) 1 2 3 Arabie Dam-Goedverwacht (right bank): existing irrigated areas
367.0
521.1
476.3
Van der Merwes Kraal - Adriaansdraai (left bank): new and existing
761.4
287.5
621.1
Veeplaats (above channel): existing new
196.5
10.3
201.6
22.1
71.7 42.5
Tooseng: new Wonderboom - Apel (right bank): - below channel - above channel new - Vlakplaats and Wonderboom - Strydkraal
309.9 107.6
32.5 207.1
176.0
27.7 131.2
41.6
330.6
4.7 76.1 91.7
TOTAL 2 279.0 2 226.0 1 865.1 Table 6 indicates the irrigation suitability of all the map units, their type and degree of limitation and the precautionary measures necessary to attain sustained irrigation use. 5. RESULTS 5.1 Extent of irrigable classes The soils demarcated during the survey, their interpreted irrigation suitability and the gross area of each individual map unit are shown on the detail soil map accompanying this report. The diagram above is a summary of the gross areas (in ha) of the irrigable classes per geographical area, the latter in various sub-divisions. 5.2 Suitability of the soils of the Tooseng area for citrus Based on the soil requirements of citrus, the map units of the Tooseng area can be sub- divided into irrigation suitability classes as follows:
Map unit Limitations Irrigation suitability
class
Gross area (ha)
dHu1 1 71.1 hdHu1 1 17.6 dHu2 1 137.2
185hdHu2 1 46.3 egldHu2 1 100.2 hdCv2 1 7.2 mHu2 Soil depth 2 417.6 hmHu2 Soil depth 2 7.7 eglmHu2 Soil depth 2 333.7 dHu4 Alkaline soil reaction 2 27.3 Oa6 Soil consistence, alkaline soil reaction 2 14.3 2Hu2 Soil depth 3 33.3 eglsHu2 Soil depth 3 14.3 gsHu2 Soil depth 3 157.6 mHu4 Soil depth, alkaline soil reaction 3 26.3 Summary: 1 379.6 2 800.6 3 231.5 Total 1 411.7
REFERENCES AYERS, R.S., 1977. Quality of water for irrigation. J. Irrigation and Drainage Div., ASCE, 103, No. IR2, 135-154. MACVICAR, C.N., DE VILLIERS, J.M., LOXTON, R.F., VERSTER, E., LAMBRECHTS, J.J.N., MERRYWEATHER, R.F., LE ROUX, J., VAN ROOYEN, T.H. & HARMSE, H.J. VON M. 1977. Soil Classification, A Binomial System for South Africa. Dept. Agric. Technical Services, Pretoria. SOIL CLASSIFICATION WORKING GROUP, 1991. Soil classification, A Taxonomic System for South Africa. Dept. Agricultural Development, Pretoria. Memoir No. 15. VERSTER, E. & VAN ROOYEN, T.H., 1987. Report on the detail reconnaissance soil survey of the Olifants River project, Lebowa. Pretoria. Unpublished report. TABLE 1 Water analysis of the Arabie Dam (Sample taken during September 1990)
CONSTITUENT SAMPLE
ARABIE DAM
pH 7.10 Electrical conductivity (mS/m) ECw 38.80 Total dissolved salts (mg/l) 248.00 Chloride (me/l) 2.68 Sulphate (me/l) 1.12 Bicarbonate (me/l) 0.08 Carbonate (me/l) 0.00 Calcium (me/l) 1.01
Magnesium (me/l) 0.98 Potassium (me/l) 0.16 Sodium (me/l) 1.73 Sodium adsorption ration (SAR) 1.00 Boron (mg/l) 0.01 pHc 9.30 Adjusted SAR 1.10
TABLE 2 Interpretation of water quality of irrigation (based on the concepts of Ayers 1977)
PROBLEM AND RELATED CONSTITUENT INTERPRETATION VALUES* Arabie Dam Salinity (ECw) None Permeability - ECw - Adj. SAR
Moderate None
Specific ion toxicity from root absorption Sodium (Adj. SAR) Chloride (me/l) Boron (me/l)
None None None
Specific ion toxicity from foliar absorption (sprinklers) Sodium (me/l) Chloride (me/l)
None None
HCO3 hazard (only with overhead sprinklers) None
186 * None - no problems are expected Moderate - increasing problems are expected with use over the long term Severe - severe problems are expected with continued use TABLE 3 Morphological properties and analytical data of selected soils
PROFILE NO 1 SOIL FORM SOIL SERIES
Oakleaf Leeufontein
Diagnostic horizon Orthic Ap Neocutanic B1 Neocutanic B2 Neocutanic B3 Depth (cm) 0-15 35-50 60-80 100-120 Colour 7.5YR3/2
Dark brown 2.5YR4/6 Strong brown
5YR3/4 Dark reddish brown
7.5YR4/4 Brown to dark brown
Mottling None None None None Structure Apedal Apedal Apedal Apedal Consistence Friable to firm Friable to firm Firm Very friable Permeability Rapid Rapid Rapid Very rapid Cutans None Faint cutanic Moderate cutanic Moderate cutanic Material coarser than 2 mm None None None None Textural class Clay loam Fine sandy loam Fine sandy loam Loamy fine sand Clay (%) 28 19 15 10
Silt (%) 19 10 7 2 Sand (%) 53 71 78 88 Coarse sand (%) 0.5 1.1 Medium sand (%) 9.4 21.1 Fine sand (%) 90.1 77.9 Exchangeable Na (me/100g soil)
0.15
0.27
Exchangeable K (me/100g soil)
0.68
0.15
Exchangeable Ca (me/100g soil)
8.84
5.28
Exchangeable Mg (me/100g soil)
4.95
2.75
S-value (me/100g soil) 14.62 8.45 S-value (me/100g clay) 44.47 CEC (me/100g soil) CEC (me/100g clay) Base saturation (%) pH.H2O
6.8
7.1
7.4
7.2
Electrical conductivity (mS/m)
40
26
23
18
187TABLE 3 Continue PROFILE NO 2 SOIL FORM SOIL SERIES
Hutton Shorrocks
Diagnostic horizon Orthic Ap Red apedal B1 Gravel layer on granite
Depth (cm) 0-15 20-25 25+ Colour 5YR3/4 Dark reddish brown 5YR3/4 Dark reddish brown Mottling None None Structure Structureless Structureless Consistence Friable Friable Permeability Rapid Rapid Cutans None None Material coarser than 2 mm 62.6% quartz gravel and small stones 49.3% quartz gravel and small
stones
Textural class Sandy clay loam Sandy clay loam Clay (%) 24 22 Silt (%) 6 8 Sand (%) 70 70 Coarse sand (%) Medium sand (%) Fine sand (%) Exchangeable Na (me/100g soil)
Exchangeable K (me/100g soil)
Exchangeable Ca (me/100g soil)
Exchangeable Mg (me/100g soil)
S-value (me/100g soil) S-value (me/100g clay) CEC (me/100g soil) CEC (me/100g clay) Base saturation (%) pH.H2O
7.1
7.7
Electrical conductivity (mS/m)
28
19
PROFILE NO 8 SOIL FORM and SERIES Oakleaf, Vaalrivier Diagnostic horizon Orthic Ap Neocutanic B1 Neocutanic B2 Alluvium C Depth (cm) 0-24 40-65 95-100 110+ Colour 7.5YR4/2 Brown to dark brown 7.5YR3/4 Dark brown 7.5YR3/4 Dark
brown
Mottling None None Faint frequent yellow
Structure Apedal Apedal Apedal Consistence Slightly hard Firm Firm Permeability Rapid Rapid Rapid Cutans None Strong cutanic Strong cutanic Material coarser than 2 mm None None None Textural class Fine sandy loam Fine sandy loam Fine sandy loam Organic material (%) Clay (%) 16 13 14 Silt (%) 12 7 9 Sand (%) 72 80 77 Coarse sand (%) 2.6 Medium sand (%) 27.9 Fine sand (%) 69.5 Exchangeable Na (me/100g soil)
Exchangeable K (me/100g soil)
Exchangeable Ca (me/100g soil)
Exchangeable Mg (me/100g soil)
S-value (me/100g soil) S-value (me/100g clay) CEC (me/100g soil) CEC (me/100g clay) Base saturation (%) pH.H2O
7.4
7.4
7.2
Electrical conductivity (mS/m)
24
17
18
188TABLE 3 Continue PROFILE NO 9 SOIL FORM SOIL SERIES
Oakleaf Leeufontein
Diagnostic horizon Orthic Ap Neocutanic B1 Neocutanic B2 Neocutanic B3 Depth (cm) 0-10 25-40 60-80 100-120 Colour 5YR3/4 Dark reddish
brown 5YR4/4 Reddish brown
5YR4/4 Reddish brown 7.5YR4/4 Brown to dark brown
Mottling None None None None Structure Weak blocky Weak moderate blocky Weak blocky Weak blocky Consistence Firm Firm Firm to friable Friable Permeability Rapid to moderate Rapid to moderate Rapid to moderate Rapid to moderate Cutans None Strong cutanic Strong cutanic Weak cutanic Material coarser than 2 mm 3.3% fine quartz gravel 0.8% quartz gravel 1.2% fine gravel 1.6% quartz gravel Textural class Clay (%) 23 30 30 22 Silt (%) 15 12 26 14 Sand (%) 62 58 54 64 Coarse sand (%) Medium sand (%) Fine sand (%) Exchangeable Na (me/100g soil)
0.46
0.33
Exchangeable K (me/100g soil)
9.34
13.06
Exchangeable Ca (me/100g soil)
3..75
3.89
Exchangeable Mg (me/100g soil)
0.26
0.61
S-value (me/100g soil) 13..81 17.89 S-value (me/100g clay) 59.63 CEC (me/100g soil) 14.25 CEC (me/100g clay) 47.50 Base saturation (%) pH.H2O
6.7
>100.00 7.1
7.2
8.0
Electrical conductivity (mS/m)
63
490
68
53
PROFILE NO 11 SOIL FORM and SERIES Vaalrivier, Lindley Diagnostic horizon Orthic Ap Pedocutanic B1 Pedocutanic B2 Pedocutanic B3 Depth (cm) 0-18 30-45 60-80 100-120 Colour 10YR3/2 Very dark
greyish 10YR3/2 Very dark greyish
10YR3/2 Very dark greyish
10YR3/3 Dark brown
Mottling None Common small diffuse grey
Common large diffuse yellow and grey
Few small diffuse yellow and grey
Structure Weak medium blocky Moderate medium blocky
Strong medium blocky Moderate medium blocky
Consistence Firm Very firm Extremely firm Very firm Permeability Slow Slow Very slow Slow Cutans None Strong cutanic Strong cutanic None Material coarser than 2 mm None None None None Textural class Sandy clay Clay Clay Clay to clay loam Clay (%) 40 47 53 45 Silt (%) 18 13 20 17 Sand (%) 42 40 27 38 Coarse sand (%) Medium sand (%) Fine sand (%) Exchangeable Na (me/100g soil)
1.74
8.70
Exchangeable K (me/100g soil)
0.62
0.22
Exchangeable Ca (me/100g soil)
11.09
11.56
Exchangeable Mg (me/100g soil)
4.72
5.37
18.17
25.85
S-value (me/100g soil) S-value (me/100g clay) CEC (me/100g soil) CEC (me/100g clay) Base saturation (%) pH.H2O
7.7
8.4
8.4
8.1
Electrical conductivity (mS/m)
56
95
110
73
189
190TABLE 3 Continue PROFILE NO 24 SOIL FORM and SERIES Hutton, Makatini Diagnostic horizon Orthic Ap Red apedal B1 Red apedal B2 Gravel layer Depth (cm) 0-15 30-45 60-67 67+ Colour 2.5YR3/6 Dark
red 2.5YR3/4 Dark reddish brown
2.5YR3/6 Dark red
Mottling None None None Structure Weak medium
blocky Weak medium blocky
Weak medium blocky
Consistence Firm Very firm Very firm Permeability Moderate Moderate to slow Moderate Cutans None Strong cutanic Strong cutanic Material coarser than 2 mm 17.3% quartz
gravel and small stones
12.5% quartz gravel 26.5% quartz gravel
Textural class Sandy clay loam Clay Clay Clay (%) 23 43 42 Silt (%) 9 11 10 Sand (%) 68 46 48 Coarse sand (%) Medium sand (%) Fine sand (%) Exchangeable Na (me/100g soil)
0.18
1.17
Exchangeable K (me/100g soil)
0.48
0.19
Exchangeable Ca (me/100g soil)
4.70
7.75
Exchangeable Mg (me/100g soil)
2.42
4.10
S-value (me/100g soil) 7.78 13.21 S-value (me/100g clay) 30.72 CEC (me/100g soil) CEC (me/100g clay) Base saturation (%) pH.H2O
7.1
7.0
6.7
Electrical conductivity (mS/m)
19
31
40
PROFILE NO 42 SOIL FORM SOIL SERIES
Hutton Shigalo
Diagnostic horizon Orthic Ap Red apedal B1 Red apedal B2 Red apedal Depth (cm) 0-15 30-45 60-80 100-110 Colour 2.5YR3/4 Dark
reddish brown 2.5YR3/4 Dark reddish brown
2.5YR3/6 Dark red 2.5YR3/6 Dark red
Mottling None None None None Structure Structureless Structureless Structureless Structureless Consistence Friable to firm Friable to firm Friable Friable Permeability Rapid Rapid Rapid Rapid Cutans None None None None Material coarser than 2 mm None 2.7% quartz gravel 6.8% fine quartz
gravel 13.8% quartz gravel and CaCO3 stones and concretions
Textural class Coarse sandy loam Coarse sandy loam Coarse sandy loam Course sandy Clay (%) 18 18 18 19 Silt (%) 8 9 9 6 Sand (%) 74 73 73 75 Coarse sand (%) 40.8 Medium sand (%) 21.9 Fine sand (%) 37.3 Exchangeable Na (me/100g soil)
0.07
0.14
Exchangeable K (me/100g soil)
0.25
0.16
Exchangeable Ca (me/100g soil)
6.46
6.38
Exchangeable Mg (me/100g soil)
2.57
3.18
S-value (me/100g soil) 9.35 9.86 S-value (me/100g clay) 54.78 CEC (me/100g soil) 11.37 CEC (me/100g clay) 63.17 Base saturation (%) pH.H2O
7.6
86.27 6.7
8.0
7.8
Electrical conductivity (mS/m)
49
67
58
42
191TABLE 3 Continue PROFILE NO 43 SOIL FORM SOIL SERIES
Valsrivier Craven
Diagnostic horizon Orthic Ap Pedocutanic B1t Pedocutanic B2ca Weathering gabbro Depth (cm) 0-20 30-45 45-80 80+ Colour 5YR3/4 Dark
reddish brown 5YR3/4 Dark reddish brown
5YR3/6 Dark reddish brown
Mottling None None None Structure Moderate coarse
blocky Strong coarse blocky Strong coarse blocky
Consistence Firm Very firm Very firm Permeability Moderate to rapid Moderate Moderate to slow Cutans None Few dark brown Few dark brown Material coarser than 2 mm 5.2% quartz gravel
and 1.2% quartz stones 1.1% gravel and soft
lime
Textural class Sandy loam Clay Clay Clay (%) 42 55 48 Silt (%) 8 7 9 Sand (%) 50 38 33 Coarse sand (%) Medium sand (%) Fine sand (%) Exchangeable Na (me/100g soil)
4.52
11.74
Exchangeable K (me/100g soil)
0.64
0.35
Exchangeable Ca (me/100g soil)
36.75
36.16
Exchangeable Mg (me/100g soil)
7.94
7.71
S-value (me/100g soil) 49.85 55.96 S-value (me/100g clay) CEC (me/100g soil) CEC (me/100g clay) Base saturation (%) pH.H2O
9.2
8.5
7.8
Electrical conductivity (mS/m)
65
310
700
TABLE 4 Selective properties and some interpretative features of the dominant soil units
Soil symbol Clay content %
Sand grade pH class General fertility status
Topsoil Subsoil Deep subsoil Hu1, Cv1 8-12 8-15 10-18 Coarse 5.5-7.0 Low Hu2 Cv2 12-20 15-25 18-30 Coarse 5.5-7.5 Low/Mod
Hu3 15-25 18-45 25-40 Coarse 6.5-7.5 Moderate Hu4, Cv3 12-20 15-25 18-30 Coarse 7.0-8.5 Moderate Oa1, Oa2 10-15 10-15 10-20 Fine 6.5-8.0 Mod/High Oa3,Oa4 15-30 15-30 10-35 Fine 6.5-8.0 Mod/High Oa5, Oa6 20-30 20-35 20-35 Coarse 6.5-7.5 Moderate
Oa7 15-25 20-35 20-35 Coarse 6.5-7.5 Moderate Va1 35-45 40-60 40-50 - 7.5-8.5 Moderate Va2 30-40 30-40 25-40 Fine 6.0-7.5 Mod/High
Du1, Du2 8-15 8-15 6-20 Fine 6.5-8.0 Mod/High Du4 25-40 15-40 15-30 Fine 6.5-8.0 Mod/High VB1 30-45 30-45 20-40 Fine 7.0-8.5 Mod/High
TABLE 5 Drainability of selected soil units
Soil symbol Soil depth limitation Average permeability of deep subsoil or underlying material
Flooding hazard
Hu1, Hu2, Hu3, Hu4, Hu5, Cv1, Cv2, Cv3
Limiting if less than 100cm deep, i.e. moderate and shallow phases
Weathering rock,, hardpan calcrete or dorbank: slow to moderate
None
Oa1, Oa2, Oa3, Oa4
None Alluvium: rapid to moderate Slight to moderate
Oa5, Oa6 None Deep subsoil: rapid None Oa7 None Deep subsoil, moderate to slow None Va1 None Weathering rock or deep subsoil: slow to moderate None Va2 None Alluvium: moderate but improving with depth Slight Du1, Du2,, Du3 None Alluvium: rapid to moderate Moderate VB1, Du4 None Alluvium: moderate but improving with depth Moderate
192TABLE 6 Irrigation suitability, recommendations and precautionary measures pertaining to map units (an abstract of the original Tables of the report)
Soil symbol Soil phase
Type and degree of limitation Irr. suit. rating
Recommendations and precautionary measures
Hu2, Cv2, dHu2
d Depth: slight 1 Efficent irrigation system
mHu2,mCv2 m Depth: moderate 2 Choice of crops limited: efficient irrigation system
gsHu2 s g
Depth: moderately severe; isolated bedrock exposure Water holding capacity: slight to moderate; abrasion of implements: moderate to high
3 No tree crops; very efficient irrigation system; adapted farming system
Oa3 Flooding hazard: slight to moderate; compaction and crusting; slight to moderate
1 Reduce tillage
Va2 Subsoil wetness: moderately severe; heavy draught requirement due to hard soil consistence and puddling of surface
3 Subsoil drainage necessary: reduce tillage; adapted farming system
Du1 Flooding hazard: moderate; variability in soil properties due to stratifications
2 Protection against flooding: present undeveloped areas sustain a riverine forest which should be protected against development
VB1 Subsoil wetness: moderately severe; heavy draught requirement due to hard soil consistence and puddling of surface; flooding hazard: moderate
3 Subsoil drainage necessary: reduce tillage; adapted farming system; protection against flooding
hLgt Depth: severe; mechanical; severe due to bedrock exposure
5 Not recommended
Note: Clearing of trees and bush and associated land preparation costs not taken into consideration Legend to the soil map Map Soil series Short description of the dominant soils symbol Dominant Other Red apedal soils of the Hutton form (Hu) on crest, mid- and footslope positions Hu2 Shorrocks Portsmouth Eutrophic non luvic course sand loam to course sand clay loam lying on
slightly weathered granite dHu2 Deep phase ((100-150 cm ) mHu2 Moderately deep phase (50-100 cm) gsHu2 Gravely phase (>20% gravel) and shallow phase (30-50 cm) hgsHu2 Slope (>3% ) and gs-phase Yellow brown apedal soils of the Clovelly form (Cv) on mid and footslope posisions Cv2 Blinkklip Shorrocks,
Dudfield Eutrophic non luvic course sand loam to course sand clay loam lying on slightly weathered granite
mCv2 Moderately deep phase (50-100 cm) Very deep (>150 cm) neokutanic soils of the Oakleaf form (Oa) Oa3 Jozini Leeufontein, Limpopo,
Koedoesvlei Dundee Brown non luvic fine sand loam to sand clay loam on permeable alluvium on the Olifants river terras
Deep (>100 cm) paraduplex pedocutanic soils of the Valsrivier form (Va) Va2 Herschel,
Arniston Koedoesvlei Sibasa
Brown to grey sand clay loam to sand clay with signs of wetness in the subsoil on alluvium with limited permeability on the Olifants river terras
Very deep (>150 cm) stratified soils of the Dundee form (Du) covering the recent riverbank Du1 Dundee
fine sand Vaalrivier, Levubu, Jozini Brown loam fine sand on very permeable alluvium
Mostly deep soils of lowlying and valley bottom positions (VB) VB1 Valsrivier,
Lindley, Koedoesvlei
Tamban-kulu
Dark grey brown structured and apedal cutanic sand clay loam to sand clay with signs of wetness in the subsoil on alluvium with limited permeability on the Olifants river terras
Very shallow and stony soils (Litosols) with many rock outcrops (L) hLgt Associated with granite; slope phase (>3% slope) Map symbol: Oa3 = So 1 = Suitability for irrigation
193
BYLAE 2 VOORBEELD 6 Detail grondopname, interpretasie en evaluering van gronde met die oog op rehabilitasie van grond wat deur mynbou aktiwiteite versteur is. Loxton, Venn and Associates (Verkort en die meegaande kaarte is nie ingesluit nie)
ABRIDGED VERSION OF ORIGINAL 50 PAGE REPORT RANDCOAL DOUGLAS COLLIERY. SOIL SURVEY OF VAN DYKSDRIFT AND DOUGLAS AREAS by Loxton, Venn and Associates, September 1994. CONTENTS: 1 INTRODUCTION 1.1 Survey area 1.2 Terms of reference 1.3 Current land use 2 SOIL AND LAND CAPABILITY 2.1 The soil forms and families 2.2 Land capability 2.3 Soil fertility 2.4.Material suitability for waste rock (opencast mined areas) rehabilitation 2.5 Material suitability for other purposes. 3 APPENDICES: – not included in this abridged version 3.1 Terms of Reference (a one page fax from consultant to client) 3.2 Abridged soil profile morphology observed during soil mapping (34pp). 3.3 Type profile descriptions and analytical data (7). 1. INTRODUCTION 1.1 SURVEY AREA The survey area is situated in Mpumalanga province. The area surveyed comprises two blocks, a small one north of the village Van Dyksdrift, and another surrounding the village Douglas. The total area occupies about 820 ha. Figure 1.1 shows the location of the two areas. 1.2 TERMS OF REFERENCE The letter written by the consultant to the client elaborating the scale of survey and products was provided in the Appendix. Soils were mapped using a hand auger along a 150m x 150m grid system. The observation sites were marked on the soil map and an abridged description of profile morphology of the almost 300 observations was provided in the Appendix. 1.3 CURRENT LAND USE A map was prepared of the current land use which includes both rural farming and peri-urban (village and golf course) uses. Stripping had commenced at Douglas section in preparation for opencast mining. 2 SOIL AND LAND CAPABILITY 2.1 THE SOIL FORMS AND FAMILIES The typical Highveld catena occupies most of the survey area with Hutton form soils occupying the upper slopes. Avalon form soils occupy the midslope positions grading into Westleigh and Longlands form soils in the valley bottoms. As is common on the Highveld where soils have developed in post-African cycle depositional materials, rock exposures and shallow soils occupy some of the lower slope positions where erosion has stripped the colluvial mantle. Relic ferricretes often underlie the Hutton form soils in upper slope positions as a capping to the underlying saprolite. The legend to the soil map is repeated as Table 2 below. This provides a description of each map unit in terms of the soil families, a generalised soil description, the land form and agricultural potential. The nature of the underlying material which limits soil productivity and/or which could be used as road metal or as a sealant is provided in the legend as is the average depth at which such material occurs. The soils commonly have a loamy fine sand to fine sand to fine sandy loam topsoil and are mesotrophic with increasing clay content in the subsoil (a luvic B21). Typically the "2200" families ("Soil Classification, A Taxonomic System for South Africa"; Soil Classification Working Group, 1991) are dominant (Suurbekom in the Hutton form, Leiden in the Clovelly form, Moorfield in the Bainsvlei form, Vryheid in the Avalon form, Croyden in the Glencoe form, Braeside in the Griffin form and Reitz in the Pinedene form). 2.2 LAND CAPABILITY The land capability classification of each unit in terms of the Chamber of Mines classification system is provided in a column of the soil legend. The total areas of each unit and the percentage of the total area occupied by each is shown in Table 1. The arable land is generally of a high quality with Avalon, Bainsvlei, Hutton, Griffin and Clovelly form soils dominant. These soils occupy more than 70 % of the area. The wilderness land is largely occupied by land which
194
has been disturbed by man through mining and other operations. Prior to these activities it was probably productive land. Table 1-Total ha and percentage of the proposed mining area occupied
Category Area (ha) Percentage I Wetland 118.2 14.4 II Arable 583.4 71.0 III Grazing 35.8 4.4 IV Wilderness 84.2 10.2 TOTAL 821.6 100.0 2.3 SOIL FERTILITY Although these are mesotrophic soils, the soils of the Middelburg district tend to be dystrophic and are acid with aluminium present at levels which can be toxic to plants sensitive to that element. Such soils respond to liming. Only a general statement regarding soil fertility can be made from a survey of this kind. It is recommended that fertiliser applications on the rehabilitated land be made on the basis of soil sampling of the actual resultant “topsoil”. The topsoil on the rehabilitated land may well comprise a mix of biologically inactive acid subsoil material with a high aluminium level such as is likely in the subsoil of profile 203 (the Avalon form soil sampled) together with topsoil from well fertilised cultivated croplands. As a general statement, grass growth on rehabilitated land is likely to respond to liming and to a moderate level of nitrogen and phosphate fertilisation and perhaps to zinc and molybdenum. It has been found that kraal manure produces responses in such soils on rehabilitated mined land. It may be that this stimulates biological activity in soils which may have little such activity. Little work has been done on this aspect. 2.4 MATERIALS SUITABILITY FOR WASTE ROCK (OPENCAST MINE AREA) REHABILITATION The column in the legend to the soil map (Table 2) showing the utilisable soil depth shows the depth of soil material that is well suited to general use in the rehabilitation of opencast mined land. The properties of these soil materials (in the natural state) which affect land use potential are as much a result of external influences as they are a result of properties of the materials themselves. Soil climate, which is the most important factor influencing crop production potential, is influenced by aerial climate, landform and position in the landscape, the nature of the soil materials and the nature of the underlying materials. The Avalon form, which is so highly sought after as a rainfed arable soil on the Highveld, owes its moist soil climate to the impeded subsoil drainage and the long gently sloping landscape (mid slope position) in which it occurs. This is a unique set of conditions which, wherever they are repeated, results in the same sequence of soil horizons. Replacement of materials over waste rock can not reproduce the conditions which are intrinsic to Avalon form soils. As much as the nature of landform, the position of the soil in the landscape, the depth of soil materials and the nature of the underlying material affect the climate of “natural” soils, these factors also affect the soil climate and thus the potential to sustain plant life on man-made soils. The nature of the topsoil material in rehabilitation is only one of the many factors influencing final land-use potential. Some soil materials are easier to work with and have a wider range of tolerances than others and can thus be regarded as “more suitable” for rehabilitation purposes than others. That depth of material which is recorded as utilisable on the soil map and on the map of utilisable soil is the depth of soil with a wide range of tolerance, it is also that soil which is utilised by plants growing on the soil. The material below this is utilised by plants to a lesser degree as the result of a variety of factors, the most important of which is landscape wetness (not necessarily a property intrinsic to the soil material itself). Shallow soils in which rock limits the “suitability”of materials constitute only 4 % of the landscape. In the rest of the landscape, ferricrete or soft plinthite is only limiting to plant roots when the fluctuating water table in the natural soil is operative. As a material, provided it is biologically activated and any chemical imbalances are corrected, it could be classified as “suitable”. Less suitable materials have been used elsewhere for rehabilitation. In the Middelburg area soft plinthite is regarded as unsuitable and this was used as the yardstick for this project. Suitability of materials for rehabilitation has been based upon the depth of normal rooting in the natural soil and not necessarily on the properties intrinsic in the soil materials because this reflects current mining practice in the Middelburg area. The material which is mapped as suitable for use in rehabilitation ranges in texture from a loamy fine sand to a sandy loam in the topsoil and from a loamy fine sand (the bleached subsoil of Longlands) to a sandy loam to sandy clay loam in the subsoil.
195
Table 2 Legend to soil map
Sym
bol
Dom
inan
t Soi
l Fo
rm a
nd F
amily
Sub-
dom
inan
t Soi
l Fa
mily
Generalised Soil Description
Dom
inan
t L
andf
orm
Cha
mbe
r of
Min
es
Lan
d
Fact
ors A
ffec
ting
Agr
icul
tura
l Po
tent
ial
Ero
dibi
lity
Obs
erva
tion
Num
ber
Sam
pled
Dep
th-li
miti
ng
Mat
eria
l Dom
inan
t (a
nd S
ub-
dom
inan
t)M
ap S
ymbo
l of
Phas
es
Util
isib
le so
il de
pth
(mm
)
Are
a (h
a)
Prod
uctio
n Po
tent
ial R
ainf
ed
Mai
ze
Hu 1 to 3 Hutton 2200
Cv2200 Gf2200 Hu2100
Reddish-brown loamy fine sand to sandy loam to sandy clay loam structureless subsoil (sometimes gravelly)
Midslope/ Upper Footslope
II Limited soil depth in shallow phases, well drained
Low to mode-rate
Saprolite, rock,
(ferricrete)
Hul Hu2 Hu3
>1500 1000-1500 500-1000
75.6 7.7 59.5
MH M ML to M
Cv 1,3 & 4
Clovelly 2200
Hu2200 Gf2200 Ms1100 (in shallow phase) Gc2100 Cv2100
Brown loamy fine sand to sandy loam top-soil on yellowish-brown fine to medium sandy clay loam structureless subsoil (sometimes gravelly)
Footslope II Moist soil climate
Low to mode-rate
96 Saprolite, rock,
(ferricrete)
Cv1 Cv3 Cv4
>1500 500-1000 250-500
10.5 104.6 13
MH ML to M L
Gf 1 Griffin 2200
Cv2200 Gf2100
Brown loamy fine sand to sandy loam topsoil on yellowish-brown fine to medium sandy clay loam structureless subsoil on reddish fine to medium sandy loam to sandy clay loam structureless subsoil
Midslope/ Upper Footslope
II Moist soil climate
Low to mode-rate
Gf1 >1500 38.1 MH
Bv2 Bainsvlei 2200
Av2200 Hu2200 (on ferricrete) Bv2100
Reddish-brown loamy fine sand to sandy loam topsoil on reddish fine to medium sandy loam to sandy clay loam structureless subsoil on soft plinthite (sometimes gravelly at transition)
Upper Footslope
II Moist soil climate
Low to mode-rate
246 Soft plinthite,
(ferricrete)
Bv2 Bv3
100-1500 500-1000
45.6 20.0
H
Av 2 & 3
Avalon 2200
Bv2200 Gc2200 Pn2200 (in lower footslope positions) Av3200
Brown loamy fine to medium sand to sandy loam topsoil on yellowish-brown fine to medium sandy loam to sandy clay loam structureless subsoil on soft plinthite (sometimes gravely at transition)
Upper Footslope
II Moist soil climate
Low to mode-rate
203,232,280
Soft plinthite,
(ferricrete) (gleycutanic)
Av2 Av3
1000-1500 500-1000
45.3 131.4
H MH to H
Gc3 Glencoe 2200
Av2200 Gc2200
Brown loamy fine sand to sandy loam topsoil on yellowish-brown fine to medium sandy clay loam structureless subsoil (occasionally gravely) on ferricrete
Footslope II Limited soil depth/ restricted drainage in certain phases
Low to mode-rate
Ferricrete, (rock),
(saprolite)
Gc3 500-1000 20.1 MH
Lo 3 Longlands 1000
Av2200 Kd1000 (in
Greyish-brown loamy fine sand topsoil on greyish-brown bleached loamy fine to
Lower Footslope
II Wet soil climate
Low Soft plinthite,
Lo3 Lo4
500-1000 43.0 0.9
L
196
lowest footslope position)
medium sand subsoil on soft plinthite, occasionally wet
(gleycutanic)
197
Table 2 (continued)
Sym
bol
Dom
inan
t Soi
l Fo
rm a
nd F
amily
Sub
dom
inan
t Soi
l Fa
mily
Generalised Soil Description
Dom
inan
t L
andf
orm
Cha
mbe
r of
Min
es
Lan
d C
lass
ifica
tion
Fact
ors A
ffec
ting
Agr
icul
tura
l Po
tent
ial
Ero
dibi
lity
Obs
erva
tion
Num
ber
Sam
pled
D
epth
-lim
iting
M
ater
ial
D
omin
ant (
and
su
b-do
min
ant)
Map
Sym
bol o
f Ph
ases
Util
isab
le so
il de
pth
(mm
)
Are
a (h
a)
Prod
uctio
n Po
tent
ial R
ainf
ed
Mai
ze
Pn 3 & 4
Pinedene 2200
Ka2000 (in lowest footslope position) Pn2100
Brown loamy fine sand to sandy loam topsoil on yellowish-brown fine to medium sandy loam to sandy clay loam subsoil on gleycutanic (wettest in lowest position in landscape)
Lower Footslope/ Valley Bottom
II Somewhat restricted drainage in most phases
Low to moderate
Gleycutanic (gley horizon)
Pn3 Pn4
500-1000 250-500
7.2 1.2
MH M
Fw 1 Fernwood 2110
Lo1000 Grey to black loamy fine to medium sand topsoil on whitish grey bleached loamy fine to medium sand subsoil (occasionally wet)
Footslope I Restricted drainage
Low (Soft plinthite) Fw1 >1500 (poor quality)
5.0 L
We 4 Westleigh 1000
- Brown loamy fine sand to sandy loam topsoil, sometimes gravelly, on soft plinthite
Footslope II Limited soil depth/ restricted drainage
Low to mod-erate
49 Soft plinthite We4 250-500
7.1 ML
Ka 5 Katspruit 2000
Ph2200/Kd1000 (in slightly higher landscape position)
Greyish-brown loamy medium to coarse sand to sandy loam topsoil on weakly to moderately structured gleyed clay
Valley Bottom
I Very poorly drained
Mod-erate
298 Gleyed material Ka5 <250 53.7
VL
Ms 4 & 5
Mispah 1100
Cv2200 Brown loamy fine to medium sand to sandy loam topsoil on rock
Midslope/ Footslope
III Very shallow soil
Very low
- Rock Ms4
250-500
7.7 L
Ms5 <250 8.1 VL
Cv/R Clovelly 2200
- As for Cv unit but very shallow with 20 – 40% rock outcrops
Midslope/ Footslope
III Rocky Non arable
Very low
- Rock Cv4/R 250-500
7.1
Ms5/R
Mispah 1100
- As for Ms unit but very shallow with 20 – 40% rock outcrops
Midslope/ Footslope
III Rocky Non arable
Very low
- Rock Ms5/R <250 6.4 VL
Ka5/R
Katspruit 2000
- As for Ka unit but very shallow with 20 – 40% rock outcrops/stones/boulders
Valley Bottom
I Rocky Non arable
Very low
- Rock/ gleyed material
Ka5/R <250 15.6
VL
Ms/R
Rock Ms1100 As for Ms5/R but with steep slopes and 50 – 90% rock outcrops
Midslope/ Footslope
IV Rocky Non arable
Very low
- Rock
Sw4/ Swartlan Reddish-brown fine sandy loam topsoil on Footslope III Rocky Non Mod- - Saprolite Sw4/R 250- 3.4 VL
198
R d 1211 reddish-brown moderately structured fine to medium sandy clay loam subsoil on weathering rock with 20-40% rock outcrops
arable erate 500
Table 2 (continued)
Sym
bol
Dom
inan
t Soi
l Fo
rm a
nd F
amily
Sub
dom
inan
t Soi
l Fa
mily
Generalised Soil Description
Dom
inan
t L
andf
orm
Cha
mbe
r of
Min
es
Lan
d C
lass
ifica
tion
Fact
ors A
ffec
ting
Agr
icul
tura
l Po
tent
ial
Ero
dibi
lity
Obs
erva
tion
Num
ber
Sam
pled
D
epth
-lim
iting
M
ater
ial
D
omin
ant (
and
su
b-do
min
ant)
Map
Sym
bol o
f Ph
ases
Util
isab
le so
il de
pth
(mm
)
Are
a (h
a)
Prod
uctio
n Po
tent
ial R
ainf
ed
Mai
ze
MISCELLANEOUS LAND CLASSES E Eroded areas IV 0.7 N
Rock Heap Waste Rock IV 2.6 N Coal Heap Coal and waste coal IV 20.6 N Disturbed Mining commenced / topsoil stripped (3) IV 29.1 N Excavation in fill Rehabilitated mine land III 3.1 L Excavation Open cast mine IV 31.2 N Note:- 1 Each symbol is made up of two letters and a number, eg Hu1. The symbol stands for the dominant soil form in the unit and the number refers to the general depth of the unit as follows: 1 = >1500 mm, 2 = 1000-1500 mm 3= 500-1000 mm, 4 = 250-500 mm, 5 = <250 mm. 2a. Erodibility was determined using the RUSLE model to produce K-Nomograph values which are classed as follows: <0.1 = very low; 0.1-0 = low; 0.2 – 0.3 = moderately high; >0.4 = high. 2b. A danger of wind erosion exists, especially in the late winter where maize lands are ploughed and especially on the upper footslope/midslope positions. The dominant topsoil sand grade in the survey area is fine, with dominant topsoil textures being from loamy and to sandy loam (6-18% clay). 3. The two areas on the soil map marked “disturbed” have been subject to removal of soil and/or mixing such that no horizon determination was possible. In the area north of the stream, much of the material has been used to construct a contour wall and the bedrock/ferricrete is exposed in many places and water has been dammed artificially. In the area south of the stream, much disturbance and mixing has occurred and coal, rock and other parent materials have been deposited over much of the area.
2.5 MATERIAL SUITABILITY FOR OTHER PURPOSES A materials survey was not conducted and the consultant can thus neither comment on the quality nor quantity (depth) of the various “other” materials that have been encountered. The soil map does however provide an indication of the best places in which various materials can be located. Pit Sand: The bleached subsoil of soil map units Fw1 and of Lo3, if it is washed, would make a suitable sand for building purposes. Clay: The subsoil of Ka5 and of Pn3 and Pn4 (in lower slope positions) are the heaviest textured materials suitable for treatment and use as sealants in the survey area.
Road metal: Rock and weathered rock (sandstone and shales) underlie most soils at various depths. The Ms4 and Ms5 units, Cv4 and Sw4 units have weathering rock at shallowest depths. Ferricrete can be found in the Hu, Cv, Bv and Av map units, however, it is most common in Gc3 where it occurs at 500-1000 mm below the yellowish brown subsoil. REFERENCES No references were given in the original report
199
SUMMARY No summary was provided in the original report MAPS The original report provided Maps drawn on an Orthophoto map base (two sheets each) at 1:10 000 scale of: 1 Soils 2 Soil stripping guide 3 Present land use
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BYLAE 2 VOORBEELD 7 Opname, interpretasie en evaluering van die gronde se geskiktheid vir ontvang van rioolafval. Loxton, Venn and Associates (Verkort en die meegaande kaarte is nie ingesluit nie) ABRIDGED REFORMATTED VERSION OF ORIGINAL 13 PAGE REPORT (Excluding soil and sludge analyses and maps) A REPORT ON THE PROPOSED DISPOSAL OF SEWAGE SLUDGE ON AGRICULTURAL LAND BY THE DUNDEE MUNICIPALITY FOR WMB, WATES, MEIRING AND BARNARD by Loxton, Venn and Associates, MAY 1993. CONTENTS 1. Introduction 2. Principles of Effluent Disposal by Agricultural Methods 3. Soil Properties that Influence Effluent Disposal 4. Water Budget 5. Effluent Disposal 6. References MAPS 1. Soil Survey for Sewage Disposal 2. Schematic Land Use Plan 1. INTRODUCTION Following a preliminary visit by the consultant to the site in March and presentation of a preliminary report, it was decided that a detailed soil survey of an expanded site was to be undertaken in order to establish the suitability of the soils to dispose of sewage sludge and to provide a measure of the quantities of sludge that could safely be applied to the soils. Sludge analyses attached to this report have tended to confirm the previous analyses. Zinc remains the limiting trace element. Boron, about which concern was previously expressed, is low. 2. PRINCIPLES OF EFFLUENT DISPOSAL BY AGRICULTURE METHODS The philosophy behind irrigated disposal of wastes is not the same as that which is used in irrigated agriculture. Optimal crop performance relative to inputs is required in agriculture . In agriculture the excess salts in irrigation water are leached out of the soil by applying water in excess of the crop requirement. When it comes to the disposal of wastes on soils, one of the most important criteria that must be adopted is that leaching of pollutants into the natural system must be avoided. The more water that is applied the greater the possibility of the transport of pollutants out of the soil. At the same time, in terms of the Conservation of Agricultural Resources Act, the soil can not be left in a contaminated unusable state. The contaminants in municipal domestic sewage that are the cause for concern (apart from microbiological considerations) include nitrogen, phosphate, zinc and boron as well as a number of heavy metals, some of which are potentially toxic to plants and/or animals when they enter the food chain. In the case of many of these the solubility can be controlled in the soil by maintaining a high pH. Most of the heavy metals do not readily move through soils. Nitrogen is the exception regarding mobility in soils. It moves fairly readily in the soil solution into natural waters and, by enriching surface waters, can result in algal blooms which, with the accompanying problems such as deoxygenation, leads to an upset in the aquatic ecology (fish deaths). Nitrogen is an essential plant nutrient and is one of those that is used most generously by actively growing plants. These levels can approach 400 kg N/ha/annum (In agriculture that level is high. Many crops such as maize can produce well with only 70 kg N/ha/annum). In terms of the volumes of nitrogen in municipal sewage and in many industrial wastes this is a small amount and nitrogen would frequently be that element which limits application rate most severely if the growing crop were the only consumer of soil applied N and if ”leakage” into the natural water system is to be prevented. This is fortunately not the full picture. Soils contain a remarkable range of bacteria. Ammonium ions are oxidised to nitrates by nitrification, while other bacteria, under anoxic conditions, derive their energy by denitrification - the transformation of nitrate to gaseous nitrogen and nitrous oxide. Very large amounts of soil applied nitrogen can be lost in this way. This loss is augmented by ammonia volatilisation, particularly in alkaline soils and in soils containing free lime (CaCO3). Some elements may be taken up by plants to levels at which they can be toxic to animals ingesting them. This varies between plants. Some plants are killed by high soil levels of such metals, other plants are unable to take up
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the metals, while others take them up freely, far in excess of any requirement they may have, without any apparent harm. As stated above, the solubility of most metals in soil can be controlled by controlling soil pH. Of the metals which are a potential problem in municipal wastes; molybdenum, selenium and boron are soluble at high pH levels. Boron is toxic to plants at elevated levels in the soil. It is essential to plants but not to animals. Molybdenum is essential to plant growth. At high levels molybdenum is not toxic to plants, in fact plants can accumulate molybdenum to levels where animals may be affected. Selenium on the other hand is not required by plants but is essential to animals. Some plants growing on soils with a high level of selenium may accumulate selenium to levels potentially toxic to animals. One approach to disposal of the waste might be to monitor the soil and waste chemistry and apply waste at that rate governed by the application of molybdenum, selenium and boron, since the other elements can be rendered insoluble by the maintenance of a high pH in the soil (by annual lime application to the soil). Under this system however it is possible that soil accumulation of heavy metals would reach a level at which the site must be considered “contaminated.” (In the sense that pH maintenance must be continued after the site is abandoned in order to prevent release of the potentially toxic elements). Such an end product is unaccepTable. South Africa does not yet have regulations laid down defining the limits in soil loading that can be allowed for each element. We can however use the USA EPA recommendations which are based on different cation exchange capacities as shown below: Table 1: Suggested loading (kg/ha) of various elements in soils at various cation exchange capacities Cation Exchange Capacity Element <5 5 - 15 >15
Cadmium 5 10 20 Copper 125 250 500 Nickel 125 250 500 Zinc 250 500 1000 Lead 500 1000 2000 Page and Chang, 1985 (from Feigin, Ravina and Stalbevet, 1991) If these levels are used, then zinc becomes that trace element in the Dundee sludge which is limiting. Based on 2 000 mg Zn/ton dry effluent, the total loading permissible on the various soils as shown in the soils legend was calculated and is shown in Table 2. Table 2 : Total and annual sludge loading permissible on various soils MAP SYMBOL TOTAL LOADING (Tons/ha) ANNUAL LOADING Tons/ha) Avalon (>15 %) 240 12 Avalon (<15 %) 120 9 Westleigh 240 12 Willowbrook 480 12-15 Swartland 480 9 Katspruit 120 9 If the planted pasture uses up 200 kg N annually and an additional 200 kg N is lost to the atmosphere through denitrification, then it can be assumed that the nitrogen in 12 tonnes/ha of dried sludge can be disposed of annually without any N accumulation in the soil. It may be possible to exceed this (for example levels of 1 000 kg N annually are being used successfully on the Transvaal Highveld - Loxton, Venn, 1989) but only careful field trials and monitoring will prove this. Table 2 shows the annual rates of disposal that are recommended on each soil type based on the ability of the soils to assimilate the nitrogen in the effluent. It is essential that soil pH be maintained above 6.5 by the annual application of agriculture lime (probably about 5 t/ha/annum - with the initial application of 10 tons lime mixed (ploughed) into the upper 50 cm of soil.
200
Table 3: Legend to the soil map
Map Symbol
Generalised Soil Description(2)
Factors Affecting Agricultural
Potential
Rainfed Maize Production Potential
Factors Affecting Sewage Sludge
Disposal
CEC
Estimated Maximum Loading (Dried Sludge)
Permissible Annual(1)
(Tons/ha) Total(1)
(Tons/ha) Av
A brown to very dark brown sandy loam overlies a yellowish brown to strong brown sandy clay loam which becomes prominently mottled red with depth and overlies a grey mottled red sandy clay which becomes grey mottled yellow with depth. (Avalon series in Binomial System).
These soils are not freely drained. Water accumulates in and above the mottled horizons for much of the average rain season keeping the yellow horizon above it fairly moist for longer periods than is the case with freely drained soils.
High With their high potential for crop production these soils will be able to facilitate the incorporation into plant tissue of large amounts of nitrogen. Anaerobic subsoil will cause denitrification of excess nitrogen. Deeper subsoil provides a good seal against deep percolation of water with potential pollutants.
5-15 12 240
Lek
A brown to very dark brown loamy sand overlies a dark yellowish brown to yellowish brown sandy loam which overlies a layer of ferricrete or iron nodules in a sandy loam which overlies weathering sandstone, in places with a yellowish brown sandy loam in the intermediate position. (Leksand series in Binomial System)
These soils are not freely drained. The low water holding capacity and relatively shallow rooting depth (40-50cm) to ferricrete give them a lower production potential than the Av (Avalon) soils although in broad terms the same factors act to produce a moister soil than normal (for the particular texture).
Moderately Low
Because these soils have a significantly lower potential for crop production, they also have a lower potential for the disposal of nitrogen. The weathering sandstone acts in much the same way as the sandy clay in Av reducing the percolation of water and potential pollutants out of the soil.
<5 9 120
West
A very dark brown sandy loam with faint rusty streaks becomes a sandy clay loam with depth, overlying a dark yellowish brown mottled strong brown sandy clay which grades into a strong brown mottled yellowish red fairly dense sandy clay. (Westleigh series in Binomial System)
These soils are not freely drained. They are wetter than the Av (Avalon) soils and remain wet for longer periods. In dry seasons they may perform as well as Av soil and better than freely drained soils but in wet seasons crops will suffer water-logging.
Moderately Low
Although these soils have a lower potential than the Av soils for incorporation of N into plant tissue, they have a higher potential for denitrification than the Lek (Leksand) soils.
5-15 12 240
201
Table 3: Legend to the soil map (continue)
Map Symbol
Generalised Soil Description(2)
Factors Affecting Agricultural
Potential
Rainfed Maize Production Potential
Factors Affecting Sewage Sludge
Disposal
CEC
Estimated Maximum Loading (Dried Sludge)
Permissible Annual(1)
(Tons/ha) Total(1)
(Tons/ha) Willow A very dark brown to black
moderate fine blocky clay overlies a black, dense clay with faint rusty streaks and specks. Generally fine gypsum crystals and fine calcium carbonate nodules occur at depth. (Willowbrook series in Binomial System)
These soils are presumed to be too wet in normal seasons to be cultivated. (They have been cultivated in the past but cultivation was abandoned sooner than in the adjacent fields). In dry years they may produce reasonable yields of crops which tolerate the heavy clay.
Low These soils, being dense and slowly permeable, will retard the movement of moisture (which could carry pollutants) through the profile. Denitrification will probably be rapid. They are difficult soils to work being sticky when wet and hard when dry. They are unsuited to maize production but pastures would do well on these soils and would dispose of nitrogen in amounts proportional to the biomass produced.
>15 12-15 480
Swart A very dark brown sandy loam overlies, with a clear of abrupt transition, a dense dark yellowish brown clay (Swartland series in Binomial System)
.
These soils have a low infiltration rate and are consequently droughty. They are also erodible.
Low Although the subsoil is dense and impermeable, these soils are not suitably for the disposal of sludge. The rate of assimilation is likely to be low.
>15 9 120
Wet The soils are comparable with those in West but occupy a position which is wetter and therefore will be more difficult to work.
These soils are too wet to allow traffic over them during the rain season. They should be regarded as non arable.
Low These soils are too wet to be regarded as arable.
<5 9 120
(1) Total loading is in terms of EPA standards. Zinc is the limiting factor. Annual loading is in terms of nitrogen. Monitoring of the system is essential. This may allow an extension of the life of the project.
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3. SOIL PROPERTIES THAT INFLUENCE DISPOSAL The legend to the soils map is repeated here, for sake of convenience, as Table 3. This provides a brief description of the soil, their properties and potential. Avalon, Westleigh and Willowbrook form soils are dominant on the proposed disposal site. These soils are not normally recommended for irrigation because the impeded drainage in the subsoil does not allow the free movement of excess salts etc. imported with irrigation water out of the soil and waterlogging and salt accumulation are consequently a greater hazard than in freely drained soils. In the longer term, unless management is perfect, irrigated crops on Avalon and Westleigh form soils will not produce as well on Hutton form soils With poor management irrigation will decrease crop performance on such soils. Willowbrook soils are too wet to cultivate during normal summer seasons. However the fact that these soils have subsoils which will react as a natural barrier to the movement of water which could carry pollutants out of the soil is a positive factor when effluent irrigation is planned. Moreover the increasing anoxic conditions with depth in the subsoil of all these soils (Leksand is the least so inclined) will result in strong denitrification processes being set up in the subsoil. From the aspect of containment and/or neutralisation of the potential pollutants, the Avalon and Westleigh form soils have valuable properties. From the crop aspect these soils are not perfect under irrigation, however good management can go a long way towards overcoming the inherent problems. 4. WATER BUDGET In the assessment of the amount of water transpired by a freely growing plant, it is the custom to use the formula (“A” Pan evaporation x K) where K is a factor that has been determined experimentally for crop plants in various stages of growth relating the amount of water evaporating from a free water surface in an “A” Pan evaporation tank. In determining the deficiency or otherwise of the rainfall it is the custom to regard only a portion of the rainfall as being effective. The “ineffective” rainfall is that lost by runoff and by evaporation from the soil. No general agreement is found in the assessment of effective rainfall. The consultant has adopted the FAO system which uses a nomograph relating evapotranspiration, rainfall and soil moisture storage capacity. The effectiveness of rainfall thus varies with all three of these factors and not only with rainfall as with most other empirical methods. Table 4 shows that a pasture crop growing in the area would require 813 mm irrigation water if it were to suffer no moisture stresses. There is a moisture deficit in every month. The calculation ER:EO shows that if it were to make effective use of the rainfall a plant would need to have a winter K factor of 0,1 increasing to 0,3 in October with a maximum of 0,5 in January to March. Such a crop would necessarily display a fair degree of drought tolerance (e.g. Old man salt bush (Atriplex sp) or Eucalyptus camaldulensis). Under rainfed conditions, most plants would go into a state of dormancy or nil growth from April to October. Irrigation during this period is essential for optimal plant growth. Table 4: Evaporation and evapotranspiration of a pasture crop, effective rainfall and monthly moisture deficit Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year A Pan Evapora-tion (EO)
223 182 168 131 120 100 116 172 200 222 216 244 2094
K (Pasture Crop)
0.8 0.8 0.8 0.7 0.6 0.5 0.5 0.5 0.6 0.7 0.8 0.8
P E T 178 146 134 92 72 50 58 86 120 155 173 195 Rainfall 139 125 102 47 22 9 12 17 37 77 114 136 837 Effective Rain- fall (ER)
107 91 75 34 20 7 9 13 29 62 90 109
Deficit 71 55 59 58 52 43 49 73 91 93 83 86 813 ER:EO 0.5 0.5 0.5 0.3 0.2 0.1 0.1 0.1 0.2 0.3 0.4 0.4 During the seven months April to October, an irrigated pasture crop would require 459 mm irrigated water for optimum growth or 56 % of the annual pasture crop water requirements. During this period where the moisture deficit exceeds the effective rainfall, the chances of a wet spell occurring such as could result in waterlogging and crop loss is less than in the rainy months. In practice the wet soils of the project area would only require “supplementary irrigation” in summer for optimum crop performance. The amount of water that is required increases in winter if an actively growing crop is on the land. The seasonal imbalance in water usage could create storage problems if reliance is placed on irrigated effluent disposal since it is only for seven months of the year that full irrigation is possible (at slightly more than 2 mm water
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per day or 15 mm water on a weekly cycle). Storage (less evaporation losses) of about six months liquid would be necessary. For this reason we have presumed that effluent disposal using a muck spreader (i.e limiting the amount of liquid applied) will be practised. 5. EFFLUENT DISPOSAL Having given due consideration to the matter of effluent disposal, we are of the opinion that if it is economically feasible the application of solids (sludge) and liquid should be undertaken as separate operations. • When necessary, storage of the liquid and its subsequent use is much easier than sludge storage with
subsequent mixing prior to application. There will be times when conditions are too wet to apply effluent to the fields without risking environmental pollution.
• Application of the solids in the effluent (in a slurry) onto the growing crop could reduce crop performance, the solids will lodge in the plant material and detract from the use to which the plant material can be put (it will be unpalaTable to livestock). Plant growth must be optimised because the plant would be the mechanism disposing of the water -through evapotranspiration.
• Irrigation of bare soil is unavoidable in the early stages of crop growth. It is however detrimental to soil structure. It has also been claimed that organic particles can block soil pores reducing infiltration rate. Erosion hazard will thus increase. Irrigation should preferably be practised onto a plant mat which will break the impact of droplets.
• The standing crop is needed in order to dispose of the water in the effluent by evapotranspiration and some of the nutrients essential to plant growth.
The properties of each soil unit (map unit) are summarised in the legend to the map (Table 3). The legend attached to the soil map provides an estimate of the tons (on a dry matter basis) of slurry that the various soil types, with an annual crop of maize, can assimilate. This estimate may be a conservative one. Monitoring of the build up of nitrogen, zinc and boron in the soil is recommended in order to ensure that the system is functioning correctly and also in order to optimise the rates of disposal. It is recommended that the land be divided into blocks or camps on the basis of the soils boundaries and that it be managed according to those boundaries. The different soil types not only have different assimilative capacities both in terms of the total sludge which can acceptably be applied over the project lifetime, but also in terms of the annual rate of application but they also have such widely differing properties that require divergent management practices. Thus if it does become necessary to utilise the area mapped (Willow) as Willowbrook series, this can only be ploughed in winter and only pasture grasses can be contemplated on these soils. The yield potential of the (Swart) Swartland series is to low to justify maize production and here too, if the area is needed for effluent disposal, pastures should be established. We would recommend that the project be initiated on the Avalon and Westleigh form soils. As shown on the soils map these comprise the following units which have the assimilative capacity as shown in Table 5. Table 5: The area and the permissible loading of the different areas of soil
Soil Series Map symbol Area (ha) Annual loading (t) Total loading (t) Avalon (Av) Eastblock 11.5 138.00 2760.0 Avalon (Av) Westblock 15.12 181.44 3628.8 Leksand (Lek) 18.7 168.30 2244.00
Westleigh (West) 13.4 160.8 3216.0 Total 58.72 - 118484.8
Mean (t/ha) 11.04 201.78 In practice it may be necessary (to achieve manageable square units) to include some Willowbrook and even Swartland form soils in the project while some Avalon and Leksand may be lost. A schematic land use plan attached to this report indicates a possible layout. We presume that effluent disposal, using a muck spreader would take place on an ongoing basis (weekly). Although the project is envisaged essentially as growing maize (whether for cattle feed or for commercial sale), there will be lengthy periods when land would be awaiting maize production. After routine incorporation of the sludge and lime into the soil, it should not be left bare and we would recommend planting Eragrostis tef (September-January) or Italian rye grass (February, March, April, May) as a cover crop on land awaiting maize
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planting (in October-November). The “disposal year” should be planned to coincide with the maize season i.e. that area on which effluent is disposed in any calendar year should be completed in September, allowing preparation and planting together with the other (winter fallow) maize land while effluent disposal then commences on the following disposal area. It is probably more practical to apply the effluent in strips rather than in blocks but it is important that disposal be preplanned and methodical. A record should be kept of application rates and areas where the effluent was applied. This will be essential to the monitoring programme. Because the addition of, particularly ammonium ions, to the soil will have a strong acidifying effect and also because acid conditions will reduce the rate of biological decomposition of the effluent it is important that the areas which gave had effluent applied be well limed. Liming is an important part of any agricultural programme when cultivation is practised. The addition of effluent increases the amount of lime required. Liming rate should be culculated on the basis of soil analyses and of effluent application rate and should preferably be done on a regular annual basis - the whole project receiving a “blanket” application with the current disposal area receiving a pro rata application together with the effluent just prior to deep ploughing. 6. REFERENCES FEIGIN, A., RAVINA, I. & SHALHEVET, J., 1991. Irrigation with Treated Sewage Effluent. Eds. Yaron B, Bresler E, Thomas GW, Van Vleck LD. Advanced Series in Agricultural Sciences 17. LOXTON,VENN AND ASSOCIATES 1991. Environmental Impact Assessment of the Proposed Effluent Disposal Project on Goedehoop. Volume 1. Confidential Report for Sastech Engineering Services. MACVICAR C.N., LOXTON R.F., LAMBRECHTS J.J.N., LE ROUX J., DE VILLIERS J.M., VERSTER E., MERRYWEATHER F.R., VAN ROOYEN T.H., HARMSE H.J.von M., 1977. Soil Classification, A Binomial System for South Africa Departement of Agricultural Technical Services. VAN DER EYK J.J., MACVICAR C.N., DE VILLIERS, J.M., 1969. Soils of the Tugela Basin. Natal Town and Regional Planning Reports, Volume 15.
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BYLAE 2 VOORBEELD 8 Intensiewe grondopname, interpretasie en evaluering van die gronde se geskiktheid vir die verbouing van appels en pere onder besproeiing. F. Ellis
REPORT ON A DETAIL SOIL SURVEY OF A FRUIT FARM UNDER IRRIGATION NEAR VILLIERSDORP, WESTERN CAPE PROVINCE
By F. Ellis
Brief Explanation: Following below is an example of a soil map (Map 1) compiled of an area near Villiersdorp, Western Cape, to be used for the production of apples and pears. The field survey consisted of an investigation, classification and coding of profile pits dug on a grid lay-out of 100m by 100m. After the completion of the soil map, a report (example of contents thereof given in Table A below) was compiled. The classification and coding of each profile pit described in a specific map unit is given in a table (e.g. Table 1 in example) and the interpretation of each map unit (e.g. important soil properties, limitations, amelioration practices and suitability is given in separate tables (e.g. Tables 2 – 4). Because the client normally does not have a soil classification book available, the relevant soil form/family information pertaining to the specific area as well as an explanation of the soil codes used is given in Appendixes at the end of the report. Table A Example of the contents of a typical report on a detail soil survey of a fruit farm
CONTENTS page 1 TERMS OF REFERENCE................................................................................................... 1 2 ALLOCATION OF RESPONSIBILITIES.......................................................................... 1 3 DESCRIPTION AND CLASSIFICATION OF SOIL PROFILES...................................... 2 3.1 General .................................................................................................................. 2 3.2 Soil Forms and Families........................................................................................ 2 4 SOIL MAP UNITS - MAP LEGEND.................................................................................. 3 5 THE SOIL MAP .................................................................................................................. 4 6 SOIL PROPERTIES OF MAP UNIT INDIVIDUALS ....................................................... 5 7 SOIL LIMITATIONS .......................................................................................................... 6 8 PHYSICAL AMELIORATION MEASURES .................................................................... 10 9 SOIL SUITABILITY ........................................................................................................... 12
TABLES 1 COMPLETE LIST OF SOIL PROFILES AND CODES ARRANGED ACCORDING TO SOIL MAP
UNITS (Appendix 2, Example 8, Table 1, attached) 2 BRIEF EXPLANATION OF THE MORE IMPORTANT SOIL PROPERTIES OF THE VARIOUS SOIL
MAP UNITS (Appendix 2, Example 8, Table 2, attached) 3 SOIL LIMITATIONS OF THE DIFFERENT MAP UNITS (Appendix 2, Example 8, Table 3, attached) 4 PHYSICAL AMELIORATION PRACTICES AND SUITABILITY FOR APPLES AND PEARS
(Appendix 2, Example 8, Table 4, attached)
APPENDIXES 1 HORIZONS AND PROPERTIES DIAGNOSTIC FOR THE SOIL FORMS 2 PROPERTIES DIAGNOSTIC FOR THE SOIL FAMILIES 3 STRUCTURE OF SOIL CODE AND EXPLANATION OF SYMBOLS
Appendix 2, Example 8, Table 4
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TABLE 4SOIL MAP LEGEND OF A FRUIT FARM NEAR VILLIERSDORPPHYSICAL AMELIORATION PRACTICES AND SUITABILITY FOR APPLES AND PEARS(Abbreviations used are explained at the end of the Table)NOTE: All depths in cm.
AMELIORATION PRACTICES--------------------------------------------------------------------------------------------- SUITABILITY AFTER
SOIL Drainage Deep soil cultivation (in cm) AMELIORATIONMAP ------------------------------------------- --------------------------------------------- -----------------------UNIT HECTARE Cut-off Deep drain Ridging Ripping Shifting Mixing APPLES PEARS
---- ------- ------- ---------- ------- ------- -------- ------ ------ -----
BLOEMDAL FORM SOIL Soils with a red apedal B horizon on unspecified material with signs of wetnessBd 1 0.5 essen recom 75 essen 50 M/MH H
AVALON FORM SOILSSoils with a yellow-brown apedal B horizon on a soft plinthic B horizonAv 1 0.6 recom essen 75+ M M
PINEDENE FORM SOILSSoils with a yellow-brown apedal B horizon on unspecified material with signs of wettnessPn 1 5.7 essen recom 75 essen 60 MH MH/H
Pn 2 1.7 essen recom 75 essen 60 MH MH/H
Pn 3 0.4 essen recom 75 essen 60 MH H
OAKLEAF FORM SOILSSoils with a neocutanic B horizon on unspecified material without signs of wetnessOa 1 3.0 recom 75 essen 60 MH/H H
GLENROSA FORM SOILSSoils with a lithocutanic B horizon directly under an orthic A horizonGs 1 3.3 essen 90 recom 40 MH/H MH/H
Gs 2 2.1 recom essen 90 recom 40 MH MH
SWARTLAND FORM SOILSSoils with a pedocutanic B horizon directly on saproliteSw 1 3.4 recom recom recom 90 essen 30-40 ML M
VALSRIVIER FORM SOILSSoils with a pedocutanic B horizon on unconsolidated material without signs of wetnessVa 1 0.5 recom recom essen 30-40 ML M
STERKSPRUIT FORM SOILSSoils with prismacutanic B horizon directly below an orthic A horizonSs 1 6.0 recom recom recom 75 essen 30-40 ML M
DUNDEE FORM SOILSSoils with an orthic A horizon on stratified alluviumDu 1 2.4 recom recom 75 ML/M ML/M
Du 2 3.1 recom 75 ML/M ML/M
Appendix 2, Example 8, Table 4
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AMELIORATION PRACTICES--------------------------------------------------------------------------------------------- SUITABILITY AFTER
SOIL Drainage Deep soil cultivation (in cm) AMELIORATIONMAP ------------------------------------------- --------------------------------------------- -----------------------UNIT HECTARE Cut-off Deep drain Ridging Ripping Shifting Mixing APPLES PEARS
---- ------- ------- ---------- ------- ------- -------- ------ ------ -----
WITBANK FORM SOILSSoils with an orthic A horizon on a man-made soil depositWb 1 2.6
CARTREF FORM SOILSSoils with an E horizon between an orthic A horizon and a lithocutanic B horizonCf 1 0.8 recom essen 90 essen 60 M M
Cf 2 2.8 recom essen 90 essen 60 M M
Cf 3 0.2 recom essen 90 essen 60 M/MH MH
ESTCOURT FORM SOILSSoils with an E horizon between an orthic A horizon and a prismacutanic B horizonEs 1 1.3 essen essen recom 60 essen 30 L ML
Es 2 2.8 essen recom recom 75 essen 50 M MH
KROONSTAD FORM SOILSSoils with an E horizon between an orthic A horizon and a G horizonKd 1 2.2 essen recom recom 75 essen 50 ML M
Kd 2 0.8 essen recom recom 75 essen 60 ML M
Kd 3 0.9 essen recom 75 essen 60 M MH
CONCORDIA FORM SOILSSoils with a podzol B horizon under an E horizon on unconsolidated material without signs of wetnessCc 1 0.7 recom essen 75 essen 60 ML/M M
LAMOTTE FORM SOILSSoils with a podzol B horizon below E horizon on unconsolidated material with signs of wetnessLt 1 2.7 essen essen 75 recom 60 L ML
Lt 2 1.8 essen essen 60+ essen 75 recom 60 ML M
Lt 3 3.0 essen essen 75 recom 60 L ML
Lt 4 1.6 essen essen 75 recom 60 ML M
FERNWOOD FORM SOILSSoils with an E horizon and no underlying B horizonFw 1 1.5 essen essen 75 recom 60 ML M
TUKULU-OAKLEAF SOIL COMPLEXSoils with a neocutanic horizon on unspecified material with and without signs of wetnessTu/Oa 0.4 recom recom 75 essen 60 MH H
Appendix 2, Example 8, Table 4
219
AMELIORATION PRACTICES--------------------------------------------------------------------------------------------- SUITABILITY AFTER
SOIL Drainage Deep soil cultivation (in cm) AMELIORATIONMAP ------------------------------------------- --------------------------------------------- -----------------------UNIT HECTARE Cut-off Deep drain Ridging Ripping Shifting Mixing APPLES PEARS
---- ------- ------- ---------- ------- ------- -------- ------ ------ -----SWARTLAND-CLOVELLY SOIL COMPLEXSoils with and without a yellow-brown apedal B horison on a pedocutanic B horizonSw/Cv 2.4 recom recom recom 75+ essen 40 M M/MH
KLAPMUTS-SWARTLAND SOIL COMPLEXSoil with and without an E horizon on a pedocutanic B horizonKm/Sw 6.0
ESTCOURT-STERKSPRUIT SOIL COMPLEXSoils with and without an E horizon on a prismacutanic B horizonEs/Ss 1.1 recom essen recom 60 recom 30-40 ML M
ESTCOURT-KLAPMUTS SOIL COMPLEXSoils with an E horizon on a prismacutanic and a pedocutanic B horizonEs/Km 2.5 essen recom recom 75 essen 40-60 M MH
KROONSTAD-ESTCOURT SOIL COMPLEXSoils with an E horizon on a G horizon and a prismacutanic B horizonKd/Es 1 1.6 essen essen recom 75 essen 30-50 ML M
Kd/Es 2 1.2 essen recom recom 80 essen 50 M MH
DUNDEE-WITBANK SOIL COMPLEXSoils with an orthic A horizon on stratified alluvium and a man-made soil depositDu/Wb 3.8 essen 75 M MH
LAMOTTE-HOUWHOEK SOIL COMPLEXSoils with a podzol B horizon below an E horizon on unconsolidated material with signs of wetness and saproliteLt/Hh 1 2.9 essen essen 75 essen 50 ML/M M
Lt/Hh 2 2.1 essen essen 90 essen 70 ML/M M
HOUWHOEK-ROCK SOIL COMPLEXSoils with a podzol B horizon below E horizon on saprolite and Rock outcropsHh/R 4.0 L L
-------TOTAL 86.4 hectares
Abbrev. Description Relative suitability Abbrev. DescriptionH High 80 - 100% essen EssentialMH Medium-High 60 - 80% recom RecommendedM Medium 40 - 60%ML Medium-Low 20 - 40%L Low 0 - 20%
Abbreviations used for table:
Appendix 2, Example 8, Table 4
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Appendix 2, Example 8, Table 4
221
Appendix 2, Example 8, Table 4
222