Soil Changes Resulting From Long-term Management Practices in Western Nigeria
1979
Aina, P. O.
Two soils at the University of Ife (Nigeria) research farm were evaluated for their physical and chemical properties under long-term pasture, bush fallow, and arable cultivation that involved three tillage techniques and two fertility levels. The cultivated plots were adjacent to the fallow plots, which were at least 1/2 ha in size. Differences in soil properties between fallow and cultivated soils were considered to be due to soil changes resulting from continuous cropping. The percentage of water stable aggregates (> 2.36 mm) in the 0- to 15-cm soil depth was highest and more stable under fallow than under bush. Stability values were 95 and 80%, respectively, under grass and bush. About 76% and 80% of these aggregates were destroyed after 5 years of continuous cropping, and 88% after 10 years. Aggregate stability of the cultivated soils ranged from one-fifth to one-third those of fallow soils. The average bulk densities were 1.24 and 1.52 g/cm³ for fallow and cultivated soils, respectively, while the reductions in porosity and saturated hydraulic conductivity were more than proportionate to the increases in bulk density of the cultivated soils. The fallow soils were about four-times higher in organic matter than the cultivated soils, which had an average organic matter content of 0.8%. The fallow soils were also higher in nitrate-nitrogen, exchangeable bases, and CEC than the cultivated soils. Soil deterioration in decreasing order was: Plow-disk-harrow > plow > no-tilage. Fertilizer treatments had no efect on soil deterioration after 10 years of continuous cropping.
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