THE FERTILITY STATUS OF SOILS ALONG THE MICROTOPOGRAPHY OF THE RIVER GALMA FADAMA AT ZARIA

THE FERTILITY STATUS OF SOILS ALONG THE MICROTOPOGRAPHY OF THE RIVER GALMA FADAMA AT ZARIA

Abstract:

The fertility status of soils of the River Galma Fadama at the Kaduna State Irrigation Scheme site at Zaria was determined along its microtopographical features (MTFs). Moving at right angle away from the bank of the river, the MTFs consist, successively, of the levee, levee-backslope or backslope (BSL), coverplain {CP), and backswamp (BSW). Soil samples were taken from three replicate sites, spaced at 100 m apart in each MTF, at three depths, 0-25, 25-50 and 50-75cm. Silt was the highest particle-size fraction in all the MTFs, except the levee where sand was the highest. The silt ranged from 12-54% with mean valves of 40, 40 43 and 45% in the levee, BSL, CP and BSW, respectively. The sand fraction followed with a range of 6-58%, and mean values of 43, 28, 37 and 19% for the successive MTFs, while clay was the lowest fraction and ranged from 12-68% and the means for the successive MTFs were 17, 32, 20 and 34%. Soil reaction varied from extremely acid to slightly acid (pH 3.6-6.0) with mean values of 4.8, 4.1, 4.8 and 4.3 for the levee, BSL, CP and BSW, respectively. The exchangeable bases (Ca, Mg, K and Na) had values whose ranges could be rated as low to high, but the mean values for the individual MTFs could be rated as medium, except K which was high in the levee and Na which was high in all MTFs, except the CP. Exchangeable acidity was relatively high ranging from 0.8-8.6 cmol(+) kg”1 soil, with mean values of 3.5, 4.6, 3.6 and 3.1 cmol( + ) kg”1 in the levee, BSL, CP and BSW respectively. The effective CEC (ECEC) ranged from 3.1-13.0 cmol(+) kg _1 with respective mean values of 7.4, 7.8, 7.6 and 7.0 cmol(+) kg”1 on the levee, BSL, CP and BSW. The CEC (NH4OAc) varied from 10.0- vii 34.0 cmol(+) kg-1 and, in the same order as ECEC, the means values were 20.4, 19.5, 16.9 and 15.1 cmol(+) kg-1 while base saturation ranged from 22-94% and the mean values for the successive MTFs were 41, 35, 41 and 42%. Organic C and total N values were generally low ( < 1.0% and < 0.2%, respectively) with low mean values in nearly all MTFs, while available P, even though generally low (< 10 mg kg-1) had some exceptionally high values (> 20 mg kg-1) in the Ap horizons of at least one site in each MTF. Among the MTFs, correlation among soil properties was greatest in the BSL, followed by the levee and CP and was least in the BSW. In decreasing order, ECEC, clay and exchangeable acidity had the highest numbers of correlations, while organic C and pH (water) had fewer numbers of correlation with other soil properties. From the selected fertility parameters, pH (both water and CaC12), organic C, total N, CEC, ECEC, clay and exchangeable acidity, the fertility status of the individual MTFs could be placed in the order BSW > CP > BSL > levee. However, due to drainage impairment, which decreased in this order of fertility ranking of the MTFs, and also due to textural variation which affect chemical properties, the intensity of cropping on the fadama was in the order BSL > levee > CP > BSW. The arithmetic modelling method of land suitability evaluation on the other hand showed that the levee, BSL, and CP were all moderatetly suitable (S2) for arable cropping, while the BSW was curently not suitable (Nl). Liming, organic matter addition and subsequent maintenance and appropriate fertilization were recommended for optimum crop production on the fadama.

THE FERTILITY STATUS OF SOILS ALONG THE MICROTOPOGRAPHY OF THE RIVER GALMA FADAMA AT ZARIA

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