Optimizing phosphate fertilizer application to reduce nutrient loss in a mustard (Brassica juncea var. tumida)-maize (Zea mays L.) rotation system in Three Gorges Reservoir area

Abstract Soil nutrient loss is considered to be one of the most important causes of agricultural ecosystem degradation, but a scarcity of comprehensive research has evaluated nutrient losses affected by the reduction in application of specific fertilizers. Here, five phosphate fertilization treatments with conventional phosphate fertilization of 300 kg P 2 O 5 ha -1 yr -1 , 3/4 conventional phosphate fertilization, 1/2 conventional phosphate fertilization, 1/4 conventional phosphate fertilization and zero phosphate fertilization were conducted in a mustard-maize rotation system of the Three Gorges Reservoir (TGR) area. The contents of nitrogen (N), phosphorus (P) and potassium (K) in surface runoff and subsurface leachate and nitrous oxide (N 2 O) emission were compared among treatments. Results indicated that reduction of phosphate fertilizer rates from that the current typical rates significantly affected soil nutrient loss in the mustard-maize rotation system in the TGR area, and the effect on surface nutrient loss and N 2 O emission were the most significant. The 3/4 and 1/2 conventional phosphate fertilization treatments have no effect on nutrient uptake in mustard and maize, but decreased soil nutrient loss. A Gaussian model fit of data showed that the application of 150–250 kg P 2 O 5  ha -1 yr -1 was most conducive in improving plant nutrient utilization. Therefore, reducing the phosphate fertilizer application by one-quarter to half of the amount used by conventional fertilization standards in the TGR area is beneficial to decrease soil nutrient loss and restore the ecological degradation of the mustard-maize rotation system.