On-Farm Evaluation of the Improved Soil Nmin–based Nitrogen Management for Summer Maize in North China Plain
2008
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.
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