On‐Farm Evaluation of the Improved Soil Nmin–based Nitrogen Management for Summer Maize in North China Plain

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Abstract
The improved soil Nmin–based N management is a promising approach to precision N management, which determines the optimum side‐dress N rates based on N target values and measured soil nitrate N content in the root soil layer at different growth stages. A total of 148 on‐farm N‐response experiments, in seven key summer maize (Zea mays L.) production regions of North China Plain (NCP) from 2003 to 2005, were conducted to evaluate the Nmin–based N management compared to traditional farmer's N practices. The recommended N rates based on the improved soil Nmin method were not significantly different ( ≤31 kg N ha−1) from those determined by yield response curves (n = 13). The average N rate determined with the soil Nmin method (157 kg N ha−1) was significantly lower than farmer's practice (263 kg N ha−1), while maize grain yield was 0.4 Mg ha−1 higher than farmer's N practice (8.5 Mg ha−1) across all sites (n = 148). As a result, the improved soil Nmin–based N management significantly increased net economic gains by $202 ha−1, reduced residual nitrate N content and N losses by 44 kg N ha−1 and 65 kg N ha−1, respectively, and improved recovery N efficiency, agronomic N efficiency and N partial factor productivity by 16%, 6 kg kg−1 and 36 kg kg−1, respectively, compared with farmer's N practice. We conclude that the improved soil Nmin–based N management can be applied for summer maize production in NCP for improved N use efficiency and reduced environmental contamination.
Funding Information
  • National Natural Science Foundation of China (30390084)

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