Towards an integrated nutrient management in crop species to improve nitrogen and phosphorus use efficiencies of Chaohu Watershed

Low nitrogen use efficiency (NUE) and phosphorus use efficiency (PUE) of crop farming has been causing serious environmental consequences. Here, we established a NUECF (nutrient use efficiency of crop farming) model with substance flow analysis (SFA) method to examine NUE and PUE of cultivating nine main crops in Chaohu Watershed in 2015. We collected data mainly from questionnaires, interview, literature, and governmental statistical yearbooks. We found that the total NUE and the total PUE were low, bellowing 12.3% and 5.2%, respectively. The nutrient inputs especially large-scale livestock manure, domestic livestock manure, and chemical fertilizers far exceeded the crop products. Different crops also showed the various patterns of nutrient use efficiencies. Rice consumed the largest nutrient inputs (807 kg N ha⁻¹ and 367 kg P ha⁻¹) and contributed the lowest nutrient use efficiencies (NUE: 5.8%, PUE: 2.7%). This was mainly resulted from its large fertilizer application intensity and the largest cultivated area. Rapeseed, vegetable, and wheat also contributed the great nutrient inputs and low nutrient use efficiencies, due to the similar reasons. Concerning the various patterns of fertilizer-application and cultivated areas of these crops, we analyzed six scenarios focusing on rice, wheat, rapeseed, and vegetable for 2030 and 2050 to explore an efficient nutrient management. We selected the four key factors including application intensity of chemical fertilizer, application rate of domestic livestock manure, application rate of large-scale livestock manure, and cultivated area to design the scenarios. The scenario results showed that though current policy of controlling chemical fertilizer application is a good start to manage nutrient, we have to enhance an integrated nutrient management, including reducing chemical fertilizers on specific crops, enlarging livestock manure, and controlling cultivated areas of specific crops. With the integrated nutrient management, we can expect the nutrient inputs to reduced by 26% and hence improve the nutrient use efficiencies efficiently from 2015 to 2050. The study managed the nutrients from examining nutrient use efficiencies among different crops, and could provide an effective way to mitigate the environmental problems from crop farming.