Tillage and Farmyard Manure Effects on Crusting Compacting Soils at Katumani, Semi-arid Kenya
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In semi-arid Kenya, the most dominant soil types are of limited agricultural productivity due to crusting and compaction. The occurrence of soil crusting and compaction is attributed to seasonal rainfall characteristics, physical soil properties and bad tillage practices. Soil crusting and compaction decrease rainwater infiltration and increase surface runoff. Seasonal rainwater losses through increased runoff volumes reduce soil moisture and hence result in agricultural drought. The objective of this study was to examine the hydrological effects of two tillage practices with and without farmyard manure on surface runoff and soil loss of crusting and compacting soils under field conditions at Katumani in semi-arid Kenya. Field investigations on rainfall characteristics, surface runoff, soil loss, soil bulk density and soil shear strength covered two rainy seasons (short and long rains) and were done on a Chromic Luvisol. The field treatments were zero tillage and conventional tillage, and two farmyard manure applications (5 and 10 Mg ha-1). The results obtained showed significant effects of conventional and zero tillage and farmyard manure on infiltration and soil moisture, surface runoff and soil loss. Soil crusting and compaction significantly influenced the hydrological response of all treatments. These responses were attributed to seasonal rainfall events of varying amounts, intensities and duration, and treatment differences in soil surface conditions and aggregation. Farmyard manure (FYM) application enhanced infiltration and reduced soil crusting, compaction, and surface runoff during the initial stages of the rainy season. But in the mid-stages of the rainy season, the effects of FYM on soil aggregation diminished. Conventional tillage without farmyard manure led to high surface runoff and soil loss in this structurally unstable soil. Zero tillage performed poorly under these soil conditions because of high soil crusting and compaction, low rainwater infiltration and subsequent increase in surface runoff generation.