Soil and nutrient losses by water erosion under mono-cropping and legume inter-cropping on sloping land
Nutrient and sediment losses from agricultural activities due to soil erosion have resulted in the loss of soil productivity and have become the dominant source of nutrient loads to fresh water. The experiment was conducted on slopping land in northern NWFP near Thana, Malakand Agency on permanent plots of mono-cropping and inter-cropping to assess soil and nutrient losses in surface runoff in comparison with bare plots. Runoff, soil and nutrient losses were monitored during both the seasons (Rabi and Kharif) for a period of 03 years. During Rabi season, the treatments maintained were wheat mono-cropping, barley-lentil inter-cropping and bare fallow while the treatments maintained during Kharif season were maize mono-cropping, maize-mungbean inter-cropping and bare fallow. The results showed that runoff, soil loss, organic matter and nutrient losses were high from bare plots as compared to cropped plots. In comparison with bare fallow, Inter-cropping reduced runoff and soil losses by more than 39% and 48% respectively. Total runoff and soil loss showed good correlation with organic matter and plant nutrient losses. The order of sediment bound nutrient loss from all plots during the experimental period was: Organic matter (organic carbon) > K > N > P. While the order of nutrient loss in runoff from all plots was: K > P > N. Losses of all nutrients in surface runoff were higher as compared to the losses of nutrients in sediment. Organic matter and nutrient losses were largely governed by the amount of surface runoff and sediment lost. It can be concluded from the results that inter-cropping proved effective cropping system for controlling long term soil, runoff and nutrient losses on the slopping land. This experiment also generated data for the construction of conservation structures in the area.