P l a n t and Soil X X X , no. 1 F e b r u a r y 1969

T H E E F F E C T O F S O M E S O I L A M E N D M E N T S

ON C H E M I C A L A N D l V I I C R O B I O L O G I C A L

P R O P E R T I E S O F AN A L K A L I S O I L

by S. A. Z. MAHMOUD, S. M. TAHA, A. EL DAMATY, and F. ANTER

Faculty of Agriculture, Ain Shams University, Cairo, Egypt, U.A.R.

INTRODUCTION

Alkali soils are distributed in many governorates of the U.A.R., especially in the Nile Delta. Gypsum among soll amendments is considered an effeetive mean of replaeing Na+ by Ca++ in alkali soils by many investigators 2 15 22 27 a3. Also good results on struc- turally deteriorated alkali soils by sulphur treatment »vere reported by other investigators s 15 20 21 al. The high pH together with the alkali salts and the bad physical properties of these soils inhibit the number and activity of microbial flora 9 10 11 16 17 25 2s

It is well known that gypsum and sulphur are used for the recla- marion of alkali soils. In view of the fact that the studies on the ef- fect of such amendments on the biological properties of the soil are scant, thereIore it was found of interest to investigate the effect of different levels of gypsum and sulphur on the bioiogical as well as the ehemical properties of the soil during the proeess of reclamation.

MATERIALS AND METHODS

A p o t cu l tu re e x p e r i m e n t was c o n d u c t e d w i t h a c l a y - t e x t u r e d alkal i soil chosen f rom TM-E1-Kebir . The chemicaI analys is of t h e chosen soff is g iven in Tab le 1.

A r e p r e s e n t a t i v e soil s ample I rom the Iu r row slice layer was air dr ied an d d iv ided in to equa l po r t i ons in 24 po ts (40 cm d i a m e t e r an d 70 cm depth) . F ive d i f fe ren t r a t e s of g y p s u m and su lphu r were added accord ing to m a t h e m a t i c a l

- - ! - -

2 S . A . Z . MAHMOUD, S. M. TAHA, A. EL DAMATY, AND F. ANTER

ca lcu la t ions in order to release t he fol lowing ad s o rb ed - s o d i u m pe rcen t ages : 100% (B), 75% (C), 50% (D) and 25% (E) and more t h a n t h e a m o u n t p rac t i - cal ly ca lcu la ted (A). These a m o u n t s were e q u i v a l e n t to 9.68, 7.26, 4.84, 2.42 and 12.10 tons of gypsum, a n d 1.80, 1.35, 0.90, 0.45 a n d 2.25 t ons of s u l p h u r pe r f a d d a n * respect ively . Fo r each t r e a t m e n t four po ts were used, two for g y p s u m a n d t he o the r two for su lphur t r e a t m e n t s . The a m o u n t of a m e n d m e n t was mixed t h o r o u g h l y w i t h t he soff in t he po ts a n d t h e soff was ex tens ive ly l eached w i t h t ap water , t h e n le i t to d r y to o b t a i n a r e p r e s e n t a t i v e sample for analysis . This l each ing process a n d s amp l ing were r epea t ed b iweekly for two m o n t h s . Soff chemica l ana lys is : pH, t o t a l soluble salts, o rganic m a r t e r per- centage, solubte ca t ions a n d anions, and exch an g eab l e ca t ions were car r ied ou t on each of the r e p r e s e n t a t i v e soff sample , la

TABLE i

Chemical analysis of the untreated soil

0.229% Exchangeable cations (me/100 g soff) Total soluble salts Soluble ions (me/100 g soil)

Carbonate 2.51 Bicarbonate 2.38

Chloride 0.65 Sulphate 0.82 Caleium + magnesium 0.46 Sodium 5.88 Potassium 0.09

Calcium + magnesium 16.33 Sodium 10.00 Potassium 2.87

Cation exchange capacity 29.20 Organic marter percentage 2.78 Caleium carbonate pereentage 7.20 pH 9.30

To ta l microf lora and spore coun t s were d e t e r m i n e d on soff e x t r a c t yeas t aga r m e d i u m 19. The a c t i n o m y c e t e s c o u n t was d e t e r m i n e d b y t h e p la t e m e t h o d on J e n s e n m e d i u m 3. The followings were d e t e r m i n e d b y t h e dilu- t ion f requency. A z o t o b a c t e r was d e t e r m i n e d on base m e d i u m 77, while n i t ro - gen f ix ing c los t r id ia were coun t ed on modif ied W i n o g r a d s k y ' s m e d i u m Nitr i f iers were d e t e r m i n e d Oll S t e p h e n s o n ' s m e d i u m a n d aerobic cellulose decomposers on D u b o s m e d i u m a.

Af te r t he desired r ec l ama t ion was r eached b y t h e m e n t i o n e d ind iv idua l t r e a t m e n t s , a n a m o u n t of 400 g of compos t was a d d e d to each p o t ( equ iva l en t to 2 % of t he soff weight) a n d t he soils were p l a n t e d w i t h c lover to show t h e effect of t he r a t e oI r e c l ama t ion on p l a n t growfll.

F r o m t h e c u l t i v a t e d po ts a n o t h e r t h r ee sets of samples for each t r e a t m e n t were t a k e n for bacter io logica l ana lys is a t t h r ee d i f fe ren t dates , n a m e l y before p lan t ing , a t f lowering a n d a f t e r cu t t ing .

RESULTS AND DISCUSSION

A. Effect o/reclamation on chemical composition R e s u l t s of so i l a n a l y s e s ( T a b l e 2) s h o w t h a t t h e so i l p H w a s r e -

d u c e d d u e t o t h e a d d i t i o n of g y p s u m o r s u l p h u r a n d t h e r e d u c t i o n

* One faddan = 1.038 acre.

GYPSUM AND SULPHUR EFFECTS ON ALKALI SOIL 3

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4 S . A . Z . MAHMOUD, S. M. TAHA, A. EL DA3/[ATY, AND F. ANTER

was more pronounced in case of full treatments where the pH drop- ped from 9.3 to 8.1.

The organic matter percent was 2.78 before treatments. It can be noticed that both gypsum and sulphur additions caused a reduction in the organic matter especially when high doses were added. This could be attributed to the effect of these amendments on the physi- cal properties of soils such as soil structure, aeration and watet percolation, etc. Microbial activities will be then accelerated. It should be also born in mind that the humus in alkali soils is partially soluble due to the presence of hydroxyl ions and could be easily leached by frequent irrigation under the conditions of this pot ex- periment. Also, high temperature which prevails in Egypt could accelerate the organic marter decomposition.

With regard to soluble ions, the disappearance of the carbonate ions could be attributed to their precipitation by calcium ions released from calcium sulphate (or formed through the reaction be- tween sulphuric acid tormed by biological oxidation of sulphur and CaCO3 initially present in soil).

The ratio of Na : Ca q- Mg in the soil solution was reduced from 12.5 in untreated soll to 1.5, 1.7, 2.0, 4.0 and 6.0 in case of gypsum treatments A, B, C, D and E. In case of the corresponding sulphur treatments the ratio was reduced to 2.5, 2.7, 3.6, 4.1 and 6.2.

Comparing the exchangeable Na+ and Ca++ fr- Mg++ of the treated and untreated soils, it appears that there is always a reduction in exchangeable Na+ accompanied by an equivalent increase of ex- changeable Ca ++ q-Mg++ (Figs. 1--4) It is also clear Irom these figures that an equilibrium was attained for the ecxhangeable cations in case of gypsum treatment after 15 days (Fig. 1 and 2). However, in case of sulphur treatments, there is a gradual decrease in ex- changeable Na+ until 45 days (Fig. 4).

The exchangeable potassium was not affected by either gypsum or sulphur addition and remained more or less stable during the reclamation process. This fact was also noticed by B ower et al. 4

From the aforementioned results it can be concluded that the effect of addition of gypsum in appropriate amounts to replace the adsorbed sodium on the clay complex is much laster and more superior to the addition of the corresponding amounts of sulphur. This is also beside the fact that the gypsum is produced in the U.A.R. and its cost is much cheaper than the cost of sulphur.

GYPSUM AND SULPHUR EFFECTS ON ALKALI SOIL

Fig.

a~ 90 ,-4

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15 30 45 60 days'.

Ef fec t of gypsum on t he pe rcen t age of exchangeab l e Ca 2+ a n d Mg 2+. For explanation o/ A, B, C, D and E see [ootnote to Table 2.

Fig. 2.

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40

30

20

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! 5 30 45 60 days

Effec t of gypsum on ehe pe rcen tage of exchangeab l e N a +.

6 S. A. Z. MAHMOUD, S. M. TAHA, A. EL DAMATY, AND F. ANTER

Fig. 3.

90 ++ ff +

+ + 80

~ 70

oJ 60

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F.ffect of sulphur on the percell t~ge of exchangeable Ca 2+ and Mg 2+.

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Effec t of sulphu~" on the loercentage o~ exchangeable Na +.

G Y P S U M A N D S U L P H U R E F F E C T S ON A L K A L I S O I L 7

B. E//ect o/ reclamation on microbial /lora 1. T o t a l m i c r o b i a l f lora. Table 3 shows the effect of addition

of different quantities of gypsum or sulphur on the total microbial flora. The low density of the total count observed in this soil could be attributed to the presence of high concentration of COa 2-, C1- and Na + ions and to the high pH value recorded in such soil.

T A B L E 3

Effeet of reclamal ion with different amounts of gypsum and sulphur on the counts of microbial flora

Gypsum treatments Sulphur treatments Group

Total count * Streptomyees * Sporeformers * Azotobacter * CI. pas ter ianum **

Nitrifiers ** Aerobic cellulose

decomposers **

Initial eount

57 37.8

2,5 1,0

450 36

36

A

68.0 13.0

0.92 3.46

38.9 80.0

140.0

B

68.5 13.5 0.97 2.59

58.2 119.0

79.0

61.6 18.3

1.35 1.62

86.4 39.0

129.0

63.7 I 62.6 25.4 I 29.2

1.75 i 1.94 1.30 1.08

100.4 183.6 58.0 54.0

97.0 119.0

64.8 13.0

1.19 3.02

78.8 80.0

119.0

B C D

65.9 62.6 62.6 14.0 17.8 24.8

1.19 1.40 1.73 1.99 1.62 1 . 3 0

99,4 108.0 205.0 66.0 45.0 60.0

138.0 80.0 80.0

62.6

30.8 2.05

1.08 237.0

43.0

108.0

* Counts in millions ** Counts in thousands

Application of gypsum or sulphur caused a significant increase in total count reaching its peak after 15 days in gypsum treatment A, and after 30 days in the case of the corresponding sulphur treat- ment. This indicates that gypsum is more effective in reclamation than sulphur. This is because sulphur oxidation to SO42- depends on many factors such as the density of sulphur oxidizing bacteria, aeration, temperature etc. The increase in the total microbial flora, showed a positive response with the amount of amended gypsum or sulphur indicating tl-tat the presence of high salt concentration and the high pH value of the soil were the limiting faetor for microbial proliferation. The count in every treatment after reaching a peak was subjected to a decrease and remained then nearly static. This was explained as due to the exhaustion of available nutrients. Chemical analysis in the same time, indeed, showed a gradual decrease in organic marter. It appears that the amount of organic matter is, the limiting factor for microbial proliferation after the removal of toxic salts, the restorement of a suitable pH and in general the improve- ment of the physico-chemical properties of the soil.

2. S p o r e f o r m e r s . Although it has been stated by several in-

8 S . A . Z . MAHMOUD, S. M. TAHA, A. EL DAMATY, AND F. ANTER

vestigators that aerobic sporeformers are present in soils in the in- active form namely the spore stage 6 7 3o, yet they were found to play an active part in U.A.R. soils IS. The initial count of spores were found to be 2.5 million representing 4.39 per cent of the total microbial flora. This percentage is however low as compared with other fertile U.A.R. soils is 24. Data indicate that as reclamation proceeded spore count decline progressively indicating that spore- formers were no longer in the inactive spore phase. Thus, spores which germinated to the vegetative phase were killed by pasteuri- zation showing the marked rednction obtained in the spore count.

3. A c t i n o m y c e t e s . The initial count of actinomycetes was found to be 37.8 millions per gram dry weight of soil constituting 64 per cent of the total population. This indicates that they are the dominant organism in such soils in which severe conditions usually exist. During the process of reclamation with either gypsum or sulphur it was found that their counts began to decrease gradually. The high count recorded before reclamation may be due to their presence in the inactive form namely the conidial stage. When con- ditions became suitable as a result of reclamation, conidia germinated giving the active mycelial phase. There may be some factors which limit their growth or sporulation such as, the excess watet used for reclamation since actinomycetes are not aquatic.

4. N o n - s y m b i o t i c n i t r o g e n f ixe r s . Azotobacter and Clostri- dia were Iound by several investigators to play an important part in nitrogen fixation in U.A.R. soils 1 12 24. The high density of these organisms could be considered as a criterion of the amount of at- mospheric nitrogen fixed 14

A. Azotobacter. The initial count was found to be one million per gram dry weight. It is however, surprising to find Azotobacter to be initially present in soll of high pH value (9.3). Such value is relatively high for Y a m a g a t e and I t a n o 32 and B u r k et al. a stated that the growth of Azotobacter appeared to stop between pH 9-10. It can be added that there may be some alkali tolerant speeies in U.A.R. soils than those reported by the aforementioned investigators. Such re- sults confirm those obtained by T a h a et al. 2s in other U.A.R. alkali soil.

A progressive increase in Azotobacter count was observed during the reclamation period. This increase in count was proportional to the amount of amended sulphur or gypsum. The high densities of

GYPSUM AND S U L P H U R EFFECTS ON ALKALI SOIL 9

Azotobacter which prevailed in the reclaimed soil confirms those reported by T a h a et al. 2s and previous investigators in fertile Egyptian soils.

B. Clostridia. The initial count was found to be 450,000 per gram dry weight. It is surprising to find that their counts are lower than those of Azotobacter. Such results are contradictory to those re- ported by many investigators 2a z6 2ü who emphasized that Clostri- dia can tolerate more severe conditions than Azotobacter.

Results showed that the application of either gypsum or sulphur generally exerted a marked reduction in the counts of Clostridia which was proportional to the amount of added gypsum or sulphur. This reduetion could be due to the effeet of amendment in improving the texture of the soil allowing high tension of oxygen to penetrate between soll particles.

5. N i t r i f i e r s . The initial count of this group was found to be 36,000 per gram dry weight. Application of gypsum or sulphur eaused a marked increase in their counts. As reclamation proceeded, their counts showed a marked decrease. The reduction in their count observed later in the reclamation period could be due to the ex- haustion of the ammonia supply necessary for their proliferation.

6. A e r o b i c c e l l u l o s e d e c o m p o s e r s . Their initial count was found to be 36.000 per gr. dry weight which is considered to be relatively low if compared with U.A.R. fertile solls. M o u b a r e k 24 and A b d e 1-H a f e z 1 reported that their counts are in the order of 1 to 2 million per g dry weight in fertile soil. A marked increase was observed in their counts early, then followed by a progressive de- erease. The deerease observed later in the reclamation period is likely to be due to the depletion of celluletic materials.

It could be concluded that Azotobacter, nitrifiers, aerobic cellu- lose decomposers showed marked increase in eounts in gypsum treat- ments than in the eorresponding sulphur treatments indieating that gypsum is more effective than sulphur in improving the biological properties of the soil.

Plant growth and microbiological properties in the redaimed soil Plant growth vigor cotfld be considered as an index of the impro-

vement of the physical, chemical and mierobiological properties of the soils after they had been subjected to different rates of gypsum and sulphur. Fig. 5 shows clearly that clover best growth was ob-

10 S . A . Z . MAHMOUD, S. M. TAHA, A. EL DAMATY, AND F. ANTER

tained in A and B treatments and then a gradual decline in growth was followed in the order of C, D and E treatments. No emergence of seedlings was observed in the unreclaimed soil and this can be attri- buted to its high alkalinity.

Fig. 5. Effect of different reclamation rates of gypsum on plant vigour. A, B, C, D and E means 12.1, 9.68, 7.26, 4.84 and 2,24 tons of gypsum per

fadden respectively.

The same trend was also observed with sulphur treatments. In fact the plant vigour was more pronounced in gypsum treatments then in the corresponding sulphur treatments.

Microbiological analysis before cultivation, at flowering and after cutting showed that high densities of total microbial flora, Azoto- bacter, Clostridium, nitrifiers and cellulose decomposers were at- tained at the flowering period (Figs. 6 and 7). Counts also showed that successive increases in the microflora were proportional to the degree of reclamation. As the level of reclamation increased counts of actinomycetes and sporeformers decreased specially at flowering period. I t should be mentioned that counts at flowering period represënts counts of soil and rhizosphere since the soil was crowded

GYPSUM AND SULPHUR EFFECTS ON ALKALI SOIL 1 1

w i t h the roo t s of c lover . Coun t s a f t e r c u t t i n g s h o w e d h ighe r levels

t h a n be fo re c u l t i v a t i o n a n d th is is due to t he h igh c o n t e n t of o rgan ic m a t t e r res idues lef t in the soil a f t e r c u t t i n g the p lan t s ,

Fig. 6.

7 " 9 ~ ( a )

7.6

0 A B C D E treatments

=i u~ (b) ~.o ~ ~ -g o ~, • > A B C D E

treatments

I A B C D E

treatments

0 A B C D E

treatments

Effect of cultivation of different reclaimed sorts on microbial counts. (a) Total count (c) Sporeformers (b) Streptomyces (d) Cellulose-decomposers

For explanation of column shadings see caption Fig. 7.

12 s . A . Z . MAHMOUD, S. M. TAHA, A. EL DAMATY, AND F. ANTER

A B C D E

~- treatments

O

~5.5 (b)

"» 5.0 õ

4.5

A B C D E =E treatments

d~

°6 f ~~ A B C D E

treatments

Fig. 7. (a) A z o t o b a c t e r (b) Clostridium pasteurianum (c) Ni t r i f iers

(c)

Effec t of cu l t i va t i on of diff icul t r ec la imed soils on microbia l counts . I = Before cu l t i va t i on

I I = A t f lowering I I I = Af ter c u t t i n g

SUMMARY

A r e p r e s e n t a t i v e a lkal i soll s ample f rom Tal -E1-Kebi r was t r e a t e d in po ts w i t h di f ferent r a t e s of g y p s u m or su lphur . These ~ m o u n t s were ca lcu la ted accord ing to the exchangeab le sod ium p resen t in t he soil. Chemica l a n d micro- biological p roper t i e s were s tud ied du r ing r e c l a m a t i o n process.

Add i t i on of g y p s u m in a p p r o p r i a t e a m o u n t s to replace exchangeab l e sod ium on t he c lay complex is r auch fas te r and more super ior to t he add i t i on of t h e co r respond ing a m o u n t s of su lphur .

Counts of t o t a l microbiM flora, Azo tobac te r , ni tr if iers , a n d aerobic ¢ellu- lose-decomposers increased as t h e r e c l a m a t i o n proceeded, on t h e o t h e r hand , coun t s of spores of aerobic sporeformers , s t r ep tomyces , a n d c los t r id ia de- creased.

GYPSUM AND S U L P H U R E F F E CT S ON ALKALI SOIL 13

C u l t i v a t i o n of s u c h r e c l a i m e d soi ts e x e r t e d b e n e f i c i a l e f f ec t o n i t s m i c r o b i a l

f lo ra . P l a n t v i g o r w h i c h w a s t a k e n as & r e s u l t a n t of t h e i m p r o v e m e n t o f t h e

p h y s i c o - c h e m i c a l a n d b i o l o g i c a l p r o p e r t i e s of t h e soil d u e to r e c l a m a t i o n w a s

f o u n d t o b e s u p e r i o r in c a se of a d d i t i o n of a n a m o u n t of g y p s u m e q u i v a l e n t

to t h e a m o u n t of a d s o r b e d s o d i u m .

Reeeived Febr. 27, 1967. Revised Aug. 1968

R E F E R E N C E S

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2 A l a d j e m , R . , E x p e r i m e n t s o n a l k a l i s o i l s d u r i n g 1938-1944by thechemis t ry sec t ion of the Royal Society of Agrieulture. Soil and Fert. 11; 11-22 (1947).

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Publishing Corporation, New York (1951). 16 L i p m a n , C. B., Toxic effeets of alkali salts in soll on soil baeteria 1-Ammonifieation

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biochemieal aetivity. Ph.D. Thesis Leeds Univ., England (1955). 19 M a h m o u d , S. A. Z., A b o R1-Fadl , M., and E 1 M o f ty , M. KH., Studies on the rhizo-

sphere mieroflora of a desert plant. Fol. Mierobiol. 9, 1-8 (1964). 20 Me G e o r g e , W. T. and G r e e n e , R. A., Oxidation of sulphur in Arizona solls and its

effeet Oll soil properties. Arizona Agr. Expt . Sta. Tech. Bull. 39, 297-325 (1935). (cf. K e l l y 15).

r

14 GYPSUM AND SULPHUR EFFECTS ON ALKALI SOIL

21 Mc George , W. T., The productive capacity of semi arid soils and the present emer- geney. Soil and Fert. 6, 78-96 (1942).

22 M c George , J. M. and Wya t t, F. A., Studies on solonetz solls of Alberta. Soil Sei. 59, 419-435 (1945).

23 Miller, C. E., Soil Fertility. John Willey and Sons Inc. New York (1955). 24 Mo ub are k, M. S. M., Addition of organic manures to Tahreer soil and their effect on

microflora and some plant nutrients. M. Sc. Thesis, Fae. of Agr. Ain Shams Univ. Cairo (1960).

25 Peck, S. S., Some bioehemieal investigations of Hawaiian soil, with speeial referenee to fertilizing with molasses (1911). (el. G r e a v e s ü).

26 Russe l l , E. J., Soil Conditions and Plant Growth. Longmans, Green & Co. 9th ed. (1961).

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