Infiltration of water into two nigerian soils under secondary forest and subsequent arable cropping

Infiltration rates into two tropical-forest soils of western Nigeria under bush fallow (natural regrowth) were found to be high, equilibrium rates about 20–25 cm/h, even after precautions were taken to ensure only vertical flow from the double-ring infiltrometer system. Horizontal flow was difficult to restrain apparently due to the presence of horizontally oriented micro-fauna channels.Ploughing and tillage operations destroyed the micro-fauna channels in the plough layer and greatly reduced the tendency for horizontal flow from a normal double-ring infiltrometer system during arable cropping. Micro-fauna activity also declined in the cultivated soils and had little effect on infiltration.When the land was shifted to arable cropping, the weak granular aggregation of the surface soil deteriorated, and by the end of the first cropping year crusts began to decrease the infiltration capacity. Crusting became more severe during the second cropping year with a further reduction in the infiltration capacity and caused the development of rather serious soil erosion. The soil body beneath the crust remained hydraulically stable for a longer period but it also began to deteriorate during the second cropping year in the Oba soil probably due to its susceptability to tillage compaction and plough pan formation.