Effect of tillage and farmyard manure on infiltration, runoff and soil loss of a crusting soil
The effects of tillage and farmyard manure application on infiltration, runoff and soil loss of a crusting Luvisol(FAOIUNESCO Classification, 1974) were investigated under field conditions from October 1992 to May 1993 (two cropping seasons) on micro plots of 2m2 at the National Dryland Farming Research Centre, Katumani, Machakos, Kenya. Four treatments (Zero tillage, ZT;Conventional tillage, CT; 5t1ha farmyard manure, 5FYM and lOt/ha farmyard manure, lOFYM) with three replicates were applied on the micro plots. The plots were left bare to eliminate the influence of vegetative cover on measured parameters. The measured parameters included runoff, soil loss, bulk density, soil shear strength, Soil penetration resistance and soil moisture content. The results obtained showed some significant changes in soil micro (cloddiness) and soil aggregation with rainfall events and soil treatments. Though soil loss was highly variable even within the same treatment and for the same amount of precipitation, it was in the order of CT > ZT > 5FYM > 10FYM. Farmyard manure was found to improve soil aggregation. At the end of February, a marked decline in soil organic matter was observed, the greatest decline being under CT. There were no significant differences at (P> 0.05) between farmyard manure treatments over the experimental period. However, there were significant differences between tillage and farmyard manure treatments at P(0.05). Runoff increased with time and treatments III the order ZT>CT>5FYM> 10FYM. The progressive increase in runoff and decrease in soil loss were attributed to an increase in soil compaction! crusting due to break down in soil aggregation by raindrop impact. The high generation of high amounts of runoff decreased infiltration and profile soil moisture. Soil shear strength and bulk density variations with the rainy season influenced soil erodibility and the moisture retention characteristics of the top soil. This study did prove the significant role of tillage and farmyard manure application in facilitating better infiltration rates, improving soil moisture, and reducing soil loss during the initial stages of the rainy season when there is no vegetative cover.