PertanikaJ. Trop. Agric. Sci. 25(1): 11-17 (2002) ISSN: 1511-3701© Universiti Putra Malaysia Press

Variability of Maize Yield and Some Soil Properties in an ExhaustivelyCultivated Field in the School of Agriculture, Ikorodu

A.S FASINADepartment of Crop Production & Horticulture

School of Agriculture, Lagos StatePolytechnic, Ikorodu

Keywords: Soil variability, maize yield variability, exhaustively cultivated, field, Ikorodu

ABSTRAK

Perubahan pengeluaran jagung dan sifat sesetengah tanah di kawasan yang ditanam rapi di Sekolah Pertanian,Ikorodu dikaji menggunakan variasi yang koefisien dan analisis regresi peWagai langkah bijak selama duatahun (1990 dan 1991). Perubahan ciri-ciri tanah dan pengeluaran jagung secara individu seperti yangditunjukkan oleh perbezaan nilai cv yang meluas. Ciri-ciri kimia tanah (ex, Ka, Ex, AvaiLP dan Zink) berubahlebih daripada ciri-ciri fizikal tanah (kapasiti pegangan air dan pasir). Perubahan ciri-ciri sesetengah tanah danpengeluaran jagung berkemungkinan jelas dipengaruhi oleh penggunaan tanah sebelumnya dan aktivitipengurusan lain di sekeliling kawasan tersebuL Pada tahun 1990, 18 ciri tanah menerangkan 92.51 % variasidalam pengeluaran jagung di kawasan tersebuL Berbanding 87.29% pada tahun 1991, setiap ciri tanahmenggunakan pengaruh berlainan ke atas pengeluaran jagung. Ciri-ciri tanah menggunakan pengaruhberlainan ke atas pengeluaran jagung. Ciri-ciri tanah yang menggunakan pengaruh kuat ke atas pengeluaranjagung dalam kawasan tanaman yang mengandungi P, potasium yang boleh berubah, jirim organik, kapasitipegangan air, kalsium yang boleh berubah, pasir dan zink. Kajian ini menekankan perubahan besar jumlahtanah dan kadar pengeluaran jagung yang boleh xvujud dalam kawasan kecil yang ditanam rapi. Pendekatanyang digunakan dalam kajian ini kelihatan munasabah untuk memperbaiki pengeluaran tanaman di kawasantersebuL Pendekatan ini mungkin berguna dalam memilih ciri-ciri tanah untuk kajian penilaian kesuburantanah.

ABSTRACT

The variability of maize yield and some soil properties in an exhaustively cultivated field in the School ofAgriculture, Ikorodu was examined using a coefficient of variation and stepwise multiple regression analysis fortwo years (1990 and 1991). The variability of individual soil properties and maize yield as indicated by cv valuesdiffered widely. Soil chemical properties (ex, Ca, Mg, Ex, Avail P and zinc) varied more than the physicalproperties of the soil (sand and water holding capacity). Variability of some soil properties and maize yield werelikely to have been markedly influenced by previous landuse and other management practices around theexhaustively cultivated field. In 1990, 18 soil properties explained 92.51 % of the variation in the yield of maizeon the exhaustively cultivated field. Compared to 87.29% in 1991, each of the soil properties exerted a differentinfluence on the yield of maize. Soil properties which exerted stronger influences on the yield of maize within thecultivated field were available P, Exchangeable Potassium, organic matter, tuater holding capacity, Exchangeablecalcium, sand and zinc. This study has highlighted the tremendous amount of soil and maize yield variabilitythat may exist within a small exhaustively cultivated field. The approach used in this study seems reasonablefor improving crop yield on the field. It would be useful for selecting different soil properties for land and soilfertility evaluation studies.

INTRODUCTION (Tomlinson 1970; Areela 1982), concentrates onMuch of the existing information on soil vari- variability. This is the component of total vari-ability, including the few on tropical soils ability observed over a considerable distance of

A.S FASINA

between two distinctly different units such asparent materials or land facets (Van Wambekeand Dual 1978). Far less attenttion has beengiven to the microvariability component, whichpertains to the local and often recurrent varia-tions on the scale of a single field (Meermanand Kang 1978).

Research reported by Kang (1977 and 1978)has shown that the effect of soil variability onthe growth and performance of crops in theinter tropical areas can be pronounced. In addi-tion, the experience of researchers as a result ofthe effect of considerable microvariability onagricultural experiments can be very frustrating.A knowledge of the degreee of microvariabilityof the soil over an area and the factors respon-sible for this variability is therefore essential forboth practical and experimental agriculture.

Presently, there is a lack of informationabout soil variability and its effects on maizeyield around the study area. In view of theproximity of Lagos to the study area wherecapital or intensive farming is accessible, it isnecessary to generate adequate information onlanduse or soil management, so as to maximisethe use of the land: crop rotation is now difficultin Lagos State because of pressure on the landfor industrial and commercial activities withinthe state. This predisposes the few available ar-eas to be put under heavy use with the aid offertilizers.

It is therefore necessary to monitor cropyield on such land so as to determine to whatextent it has been altered. This will offer infor-mation regarding measures to guarantee opti-mal use of such areas.

Soil exhibits tremendous variations both lat-erally and vertically. The results of previous soilveritability studies (Ogunkunle 1986) have re-vealed very high variations between soil proper-ties of two closely spaced spots 10 cm apart on auniform terrain.

It has also been established that, for mostarable crops, the control of crop performance ismainly in the plough layer (0-20cm), wheremost of the roots are concentrated. Similarly,Sopher and McCracken (1973) found that 70%of corn yield variation was due to soil propertiesof the plough layer. Lai et al (1975) also ob-served that the removal of 2.5cm and 7.5cm ofthe topsoil, respectively resulted in 50 and 90per cent reductions in maize yield.

This study examined the degree of variationin some soil properties and yield of maize on anexhaustively cultivated field. This study will nodoubt furnish some information on the varia-tion of some soil properties and yield of maize,which we hope will be a useful guide to farmersand other landusers. Hence, the information onthe topsoil properties controlling yield variationwill be very useful for improving food produc-tion.

Study Area

The studies were conducted in the experimentalfarm of the School of Agriculture, Ikorodu. Thelocation is about 15km from Lagos and 30kmfrom Sagamu. The area lies roughly betweenlatitudes 5° 7°N and 5° 10°N and longitudes 3°16and 5° 18° ease of Greenwich Meridian. It has analtitude of about 50 km above sea level.

The climate is humid tropical with two dis-tinct seasons - the dry (November to March)and the wet (April to October). Mean annualrainfall is at least 132 mm with a maximum inJuly and September. Mean daily temperatureranges from 25 to 28°C. The humidity is highthroughout the year and reaches its peak duringthe wet season. The mean relative humidity isnever below 65%.

The soil has been mapped as Alfisols withTypic Paloustalf as the modal profile (Fasina1989). It is derived from sedimentary parentmaterial (Moss 1957) with sandy loam and sandyclay texture in the surface and subsoil, respec-tively. The soil has been exhaustively cultivatedwith vegetables and maize in the past. Thismeans the continuous planting of the field withvegetables and maize without allowing it to fal-low.

MATERIALS AND METHODS

Field studies were conducted for two years (1990and 1991) during the wet season. TZSR-Y maizeneeds variety were planted on plots of 0.1 hawith inter and inter-row spacings of 90cm and30cm respectively. NPK (15-15-15) compoundedfertilizer and urea were applied at the rate of200kg/ha and lOOkg/ha two weeks after plant-ing respectively. Leaving out the guard rows, 20maize stands were randomly selected from themiddle of the O.lha plots for the two year study.At tasselling, 5 surface (0-15cm) core soil sam-ples were taken from around each of the se-

12 PERTANIKAJ. TROP. AGRIC. SCI. VOL. 25 NO. 1, 2002

VARIABILITY OF MAIZE YIELD AND SOME SOIL PROPERTIES IN AN EXHAUSTIVELY CULTIVATED FIELD

lected stands to form a composite sample forlaboratory analysis. The maize cobs were har-vested at maturity (15% moisture content) fromthese stands and the yield per stand (weight ofgrains in grams) was determined. All experi-mental procedures were the same for both years.

Laboratory Analysis

Particle size distribution was done using theBouyoucos hydrometer method (Day 1965) andpH was measured in water (1:1, soihwater). Theexchangeable cations (Ca, Mg, Na and K) wereextracted in IN NH4OAC and Na and K weredetermined by a flame photometer and Ca andMg on an atomic absorption spectrophotom-eter. The exchangeable acidity (Al and FT) wasdetermined by titration of the soil solution withIN KCL and organic carbon was determined bythe Walkey-Black method (Allison 1965).

Available P was extracted by Bray's PI solu-tion (Bray and Kurtz 1945) and determinedfollowing the Murphy and Rilley method(Murphy and Rilley 1962). Total N was deter-mined by the macro-kjeldahl method (Bromner1960) and moisture content (%) by gravimetrics.The dicronutrients were leached out with 0.1m

NHCI (Wear and Sammer 1948) and were readon the atomic absorption spectrophotometer.

Statistical Analysis

Yield and laboratory data were statistically ana-lysed from plots for variations (mean (X), stand-ard deviation (sd). The coefficient of variation(cv) and the stepwise regressions of yield on soilproperties were measured using the SPSS com-puter program of Lagos State, Agricultural De-velopment Project, Lagos.

RESULTS AND DICUSSIONVariations in Soil Properties and Maize YieldVariability of individual soil properties and maizeyield as indicated by cv values differed widely(Table 1). The exhaustively cultivated field wasmore uniform in those soil properties which aregenetically and morphologically important suchas sand, while those properties which are ephem-eral and which are related to management (Ex,Ca, Mg, Avail.P, Ex K) were more variable (Ta-ble 1). These are the properties that most con-trol maize yield on the field. The cv data ob-tained for the two year experiment seems to be

TABLE 1Variability of maize yield and soil properties

1990 1991

Property of Maize Yield Sd CV% SD cv%Maize yield (kg)35.11Soil pH

Organic carbon %14.2Total N %Available Phosphorus Cmol kg"1

Calcium (ca) Cmol kg"1

Magnesium (mg) Cmol kg-1

Sodium (Na) Cmol kg 1

Potassium (K) Cmol kg1

Exchangeable acidity Cmol kg1

Cation Exchanged Capacity Cmol kg-1

Base saturation (BS) %Manganese (Mn) - Cmol kg1

Iron (Fe) - Cmol kg4

Copper (Cu) - Cmol kg1

Zinc (Zn) - Cmol kg"1

Sand- %Silt - %Clay - %

Water Holding Capacity (WHC) %

0.24 1.08 37 126.75 44.83

6.76

0.1252.492.471.150.270.170.244.44

94.5569.3721.681.486.670.799.0012.4035.61

0.221.41

0.0128.430.920.180.050.090.081.032.565.334.600.192.482.381.542.015.01

30.11

85437161754335382113373171614

6.788

0.3273.992.601.230.310.200.282.69

93.5571.5821.031.566.8776.159.3014.5536.72

0.133.16

0.0553.440.740.15

110.070.120.293.008.623.890.152.992.501.772.551.77

1.910.45

15.6272.2228.4612.1935.4835.0

52.5511

3.2012.0418.499.6743.523.2819.0317.524.82

PERTANIKAJ. TROP. AGRIC. SCI. VOL. 25 NO. 1, 2002

A.S FASINA

uniform. Also, the cv values obtained for soilproperties in this study were not at variance withwhat other workers have observed in the past(Beckett and Webster 1971; Chickezie 1984;Unwni 1985; Fasina 1986). The cv values ofsome chemical properties appeared to be lessvariable than others. Soil pH base saturation,CEC, total N, manganese and organic carbonwere less variable while available P, Ex, Ca, K,Zn, Ex acidity, Fe were more variable on theexhaustively cultivated land. The observed dif-ferences in the variability of the chemical prop-erties for the whole area as shown by the cvvalues (Table 1) could be due to variationsimposed by cultivation and management prac-tices employed in the study area.

It has also been shown (Beckett and Webster1971) that in cultivated areas, contrasting crops,soil amelioration and addition of fertilizers su-perimposed differences between fields on thevariation already present in the native soil. Thevariation in these chemical properties in the soilwould result in variations in the yield of cropcultivated on the field as in the case of thisstudy. This is in accordance with Talukdar andBarthakur (1986) and Gbadegesin (1987). Thevariations observed in these chemical propertiescould also be caused by land clearing and prepa-ration that the exhaustively cultivated field hasbeen subjected to over the years. The cv valuesobtained from maize yield and soil properties inthe study when grouped by the method ofWilding and Drees (1978) (Table 2) has put pH,Org C, Total N, base sat Mn, Sand, Cu, ECE, asthe least variable properties (CV 15%). Ex.Mg,Ex Na, acidity Fe, silt and clay are moderatelyvariable properties (CV 15-35%) while maizeyield, available P, Ex. Ca, Ex K and zinc areextremely variable properties (CV 35%). Theresult of this grouping agreed with the resultsobtained by Wilding and Drees (1978) and alsowith results obtained elsewhere in Nigeria (Fasina1986; Ogunkunle 1986).

It has been shown that in experiments wherespecific treatments were applied, variability ashigh as cv 99% may invalidate the results evenwith a high degree of replication (Ogunkunle1988). This shows the importance of calculatingthe variations in yield data obtained in an ex-periment.

The variation in the maize yield also signi-fied the variation in soil properties of the ex-haustively cultivated field. The variations in soilproperties and the type of management systemsadopted are thus among the causes of variationsin yield parameters observed on the field.

Yield Prediction

In order to have an idea of the contributions ofeach of the individual soil properties to thevariations in the yield of maize on the exhaus-tively cultivated land, a further analysis of thedata was carried out using a stepwise regressionmodel.

The stepwise regression of the maize yield(dependent variable) on the soil properties (in-dependent variables) reveal that 18 soil proper-ties contributed significantly (P 0.01) to theprediction of maize yield in the study area (1990-R2 value of 92.51%, 1991 - R2 value of 87.29%)(Table 3). With 8 soil properties in regression,72% of the variations in maize yield were ex-plained in 1990 while it was 75% for 1991. Theregression analysis also revealed that the soilvariables were not equal as far as their influenceon the yield of the crop was concerned. Thesoil chemical properties seemed to exert astronger influence on the yield of the crop inthe study area.

For instance, for the two year study Ex Caand organic carbon were among the first tworelevant soil properties (Table 3) that contrib-uted significantly to the yield of maize. Theregression values obtained for Available P andEx Ca (R2 = 10% - 1990, R2 = 4% - 1991) and (R2

• 10% R2 - 13% - 1991) tend to support the

TABLE 2Grouping of maize yield and soil properties using CV values for the exhaustively cultivated fields

Group of Properties Range of CV Values Soil Property and Maize Yield

Least Variable

Moderately VariableExtremely Variable

15%

15 - 35%35%

pH, org C, total N, Base Saturation, Mn Sand, Cu,CECEx. Mg. Ex Na. Ex. Acidity Fe, Silt and ClayAvail P, Ex Ca, Ex K and Zinc, Maize yield

14 PERTANIKAJ. TROP. AGRIC. SCI. VOL. 25 NO. 1, 2002

VARIABIUTY OF MAIZE YIELD AND SOME SOIL PROPERTIES IN AN EXHAUSTIVELY CULTIVATED FIELD

No. of SoilProperties inRegression

TABLE 3(a)Yield prediction (R2) with increasing number of properties in regression (1990)

List of Properties R2 R2%

1 Av.P2 Av. P. Ca3 Av. P2Ca, org. C4 Av. P. Ca. org C, WHC5 Av. P. Ca. org C. WHC, Na6 Av. P, Ca, org C, WHC, Na, K7 Av.P, Ca, org C, Whc, Na K, Base Sat.8 Av.P. Ca, org C, WHC, Na, K, B. Sat. Silt9 Av.P. Ca, org L, WHC, Na, K, Bsal10 Av.P, Ca, org C, WHC, Na K.B. Sat Silt, Zn, Fe11 Av.P, Ca, org C, WHC, Na, KB. Sat, Silt Cu, Fe, Sand12 Av.P, Ca, org C, WHC, Na, K, B.Sat, silt, Zn, Fe, Sand, Cu13 Av.P, Ca, org C, WHC, Na, K,B.Sat, Silt, Zn, Fe, sand, Cu, Mn14 Av.P, Ca, org C, WHC, Na, K.B.Sat, silt, Zn, Fe, Sand, Cu, Mn, CEC15 Av.P, Ca, org C, WHC, Na, K,B.Sat, Silt, Zn, Fe, sand, Cu, Mn, CEC, Ph16 Av.P, Ca, org C, WHC, Na, K.B.Sat, Silt, Zn, Fe, Sand, Cu, Mn, CEC, PH

Total N17 A.P, Ca, org C, WHC, Na, K, B.Sat, Silt, Zn, Fe, Sand, Cu, Mn, CEC, PH,

Total N, Mg18 Av.P, Ca, org C, WHC, Na, K, B.Sat, Silt, Zn, Fe, Sand, Cu, Mn, CEC, PH

Total N, Mg Ex ac

243441485562687276798285889091

91.6

91.85

92.51

-107777644333321

0.6

0.25

0.66

TABLE 3(b)Yield prediction (R2) with increasing number of properties in regression (1991)

No. of SoilProperties inRegression

12345678910111213141516

17

18

List of Properties R2 R2%

WHCWHC, CaWHC, Ca, Org CWHC, Ca, Org C, SiltWHC, Ca, Org C, Silt, ECWHC, Ca, Org C, Silt, Ec, CuWHC, Ca, Org C, Silt, Ec, Cu, SandWHC, Ca, Org C, Silt, Ec, Cu, Sand, Av.PWHC, Ca, Org C, Silt, Ec, Cu, Sand, Av.P, PHWHC, Ca, Org C, Silt, Ec, Cu, Sand, Av.P, PH, FeWHC, Ca, Org C, Silt, Ec, Cu, Sand, Av.P, PH, Fe NaWHC, Ca, Org C, Silt, Ec, Cu, Sand, Av.P, PH, Fe NaWHC, Ca, Org C, Silt, Ec, Cu, Sand, Av.P, PH, Fe Na, K, Zn,MgWHC, Ca, Org C, Silt, Ec, Cu, Sand, Av.P, PH, Fe, Na, K, Zn, MgWHC, Ca, Org C, Silt, Ec, Cu, Sand, Av.P, PH, Fe, Na, K, Zn, Mg, MnWHC, Ca, Org C, Silt, Ec, Cu, Sand, Av.P, PH, Fe,Na, K, Zn, Mg, Mn, Total NWHC, Ca, Org C, Silt, Ec, Cu, Sand, Av.P, PH, Fe,Na, K, Zn, Mg, Mn, Total N, CECWHC, Ca, Org C, Silt, Ec, Cu, Sand, Av.P, PH, Fe,Na, K, Zn, Mg, Mn, Total N, CEC, Ex ac

15283847556371757982

84.585.5

86.8487.07

87.20

87.26

87.29

_13109888443

2.51

0.340.23

0.13

0.06

0.03

PERTANIKAJ. TROP. AGRIC. SCI. VOL. 25 NO. 1, 2002 15

A.S FASINA

results of the coefficient of variation for thesetwo properties in the study area (Tables 1 and3). The regression also showed the importanceof different soil properties in predicting theyield of maize in the field. The differences ob-served in the yield predictions might be due notonly to the individually soil properties but to acombination of crop and soil factors.

Application of Data to Land and Soil FertilityEvaluation Studies

The soil properties observed to be controllingthe yield from the exhaustively cultivated fieldfor the two year experiment (Available P, Ex Ca,Ex K, organic matter and water holding capac-ity, sand and zinc) can be used to evolve a rea-sonable land evaluation report (sutiability/landcapability classification) for the area of study.These soil properties, when combined with otherpermanent properties of the soil like slope,depth, texture, structure and degree of manage-ment can be used for proper landuse and fertil-ity evalution studies.

The results of the regression analysis canalso be useful in soil fertility evaluation studies -in terms of artificial soil nutrient require-ments(optimum levels of nutrients), and theexpected performance and crop yields. Thiswould then make the study more relevant forcrop production.

CONCLUSIONVariability of individual soil properties and maizeyield as indicated by cv values differed widely.Soil chemical properties were more variable thanthe physical properties of the soil. The variabil-ity of some soil chemical properties and maizeyield were likely to have been markedly influ-enced by past land-use activities and some othermanagement practices around the study area. Itwas also observed from the study that variationsin some soil properties especially chemicals(Available phosphorus, Ex Ca, Calcium and Po-tassium) properties might lead to variations inmaize yield on the field.

With 18 soil properties in regression in 1990,92.51% of the variations in yield of maize wasexplained, while for 1991 the same 18 soil prop-erties explained 87.29% in maize variation. Thetwo most relevant soil properties that contrib-uted significantly to the yield of maize were Exca and organic carbon for the two year study.

The soil chemical properties exert stronger in-fluence on the yield of crop in the study area.

The soil properties found to be relevant tomaize yield in this study, if combined with themore permanent characteristics (slope, depth,drainage), may produce reliable landuse classes.Also, the results can be useful in soil fertilityevaluation studies - determining optimum levelsof nutrients and concentrating more on themost relevant soil properties, thereby saving coston fertilizer use.

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VARIABILITY OF MAIZE YIELD AND SOME SOIL PROPERTIES IN AN EXHAUSTIVELY CULTIVATED FIELD

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(Received: 28 July 1998)(Accepted: 25 September 2001)

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