Nitrogen surface runoff losses from a Chinese cabbage field under different nitrogen treatments in the Taihu Lake Basin, China

The excessive use of nitrogen (N) fertilizer for crop production can cause substantial N losses through surface runoff, generating serious nonpoint pollution. A thorough understanding of N runoff losses is necessary for optimal N management in vegetable production systems. A 3-year field experiment was conducted at a Chinese cabbage field in the Taihu Lake Basin of China to evaluate the characteristics of N runoff losses and the effect of different N fertilizer treatments on N runoff losses during the autumn and winter, 2010-2012. The results demonstrated that surface runoff was significantly and positively related to rainfall. The highest risk of N runoff loss occurred one week after fertilization, and top dressing increased this risk. NO3−-N was the main runoff component, accounting for 49.32-71.82% of the total N losses. The concentration of NO3−-N was significantly and positively related to the concentration of total N in the runoff. Significant differences in N runoff losses were observed between N fertilizer treatments. N runoff losses from conventional fertilizer were 10.43-22.68 kg ha−1, significantly higher than from other treatments, and the total N net runoff loss rates for conventional fertilizer treatment were 3.48-7.56%. The application of organic fertilizer reduced N runoff loss by 15.70-18.14% compared to conventional fertilizer application. Organic-inorganic compound fertilizer reduced N runoff loss by 27.37-36.27% compared with conventional fertilizer. Slow-release fertilizers had very significant positive effects in controlling N runoff loss, with a 58.29-61.01% reduction for sulfur-coated urea, a 49.33-56.05% reduction for biological carbon power urea, and a 59.79-63.59% reduction for bulk-blend controlled-release fertilizer relative to conventional fertilizer. This study provides vital baseline information for fertilizer choice and management practices, which can be used to reduce N runoff losses and encourage the development of new fertilizer strategies for vegetable planting.