Rainfall Simulation for Estimation of Soil and Nutrient Losses under Different Cropping Systems

Soil erosion and sediment loss are a serious threat to crop production and the environment. A study was conducted to quantify the loss of soil sediment and associated nutrients under different cropping systems using rainfall simulation. Sediment and nutrient losses and runoff water were assessed using the runoff-plot technique in the research field of the National Maize Research Programme (NMRP) and farms of Agriculture and Forestry University (AFU), Rampur, Chitwan, Nepal, during early spring 2022. Twenty-four initial soil samples were collected from the topsoil of the experimental sites to determine the initial nutrient status of the soil. Rainfall was then simulated for approximately half an hour at an intensity of 58±3 mm hr-1 from a height of 5 m above the ground. Runoff samples and sediments were collected from a 0.5936 m2 runoff plot and analysed for nutrient loss in the laboratories. The highest runoff flow (147 thousand Liter ha-1) and the highest sediment loss was observed under recently tilled vegetable field with exposed soil (842.3 kg ha-1) and the lowest in fallow land (12.3 kg ha-1). Also, the exposed plot had the highest amounts of nitrogen (N) and potassium (K) eroded: 0.306%, and 431.2 kg ha-1, respectively. However, the highest concentration of Phosphorous (P) was found in the sediments eroded from buckwheat field. The enrichment ratio was greater than 1 for all plots except for fallow land covered with grasses. Soil erosion directly contributes to soil nutrient depletion; however, integrated soil fertility management associated with legume-based cropping systems and mulching may reduce its effects on croplands, and these effects can be quantified using rainfall simulation experiments.