Abstract:
Proper agricultural land management strategies improve soil structural
properties, thereby reducing soil loss by water erosion. This study was conducted to
estimate soil losses from plots of different agricultural land management using the
Water Erosion Prediction Project (WEPP) (95.7) model. The study took place in a
semiarid region in Kenya. The mean annual rainfall was 694 mm. The WEPP (95.7)
model was initially used to estimate total sediment loading from the catchment into a
reservoir. The estimate was about 2871 t corresponding to an average sedimentation
rate of 1063 t km"" year"', which was about 76% of the measured total sediment inflow
into the reservoir. Soil losses were estimated within 10 plots on the catchment of
different sizes and slopes with the following treatments: conventional tillage (hand
hoeing) with maize and soybean intercropping (HOCOBE); conservation tillage (disc
plough) with maize and soybean intercropping (COBEAN); conservation tillage with
only maize cultivation (CNTCORN); and conservation tillage with only soybean
cultivation (CNTBEAN). The soil loss reduction of COBEAN, CNTCORN and
CNTBEAN relative to HOCOBE ranged between 27-47%, 16-29% and 12-25%,
respectively, depending on the size and slope of the plot. In general, conservation
tillage reduced soil loss relative to conventional tillage. However, with conservation
tillage, the single cropping system resulted in greater soil loss than the intercropping
system. In the case of single cropping with conservation tillage, the soil loss reduction
for maize ranged between 4 and 9%, relative to soybean. Overall, the study showed
that there would be a significant reduction of soil losses from plots if conservation
tillage with an intercropping system (maize and soybean) were to be adopted on
agricultural lands in semiarid regions
