Evaluation of nitrogen balance on pig/crop farm systems in Jiulong River watershed, China

摘要

Field surplus nitrogen and farm disposal nitrogen (N) are major sources of environmental pollution in farm systems. The purpose of this study was to use nitrogen balances at the field and farm level approaches to estimate the effects of pig production in the Jiulong River watershed, Fujian province, China, on nitrogen losses to the environment on 67 pig farms. The field surplus nitrogen ranged from 6.19 to 18.19 t nitrogen ha~(-1), which was caused by high pig density and excessive application of manure. Manure application rates of more than 450 to 510 kg nitrogen ha ~(-1) would increase the potential nitrate concentration to more than 10 to 20 mg l~(-1). Therefore, 44 to 48 heads of pig ha~(-1) was suggested to as the environmental capacity for sustaining optimal nitrogen cycling in pig farms in the Jiulong River watershed. The majority of farms have potential environmental risks because of high farm nitrogen imbalances. With more than a 2:1 ratio of N inputs to outputs, N inputs were 50 percent higher than outputs. Feed was the main input source, while pig production and manure exported were the major managed outputs. Based on the farm nitrogen balance calculation, the management options that would contribute to a more favorable nitrogen balance were also identified.