Closing the yield gap and achieving high N use efficiency and low apparent N losses

Drip irrigation under plastic mulch (DIPM) has been used to achieve high maize yields in China, but N use efficiency is often low and N losses are high. Here, we designed a DIPM system with optimal N management to close the maize yield gap with high NUE and low N loss and used it in Northeast China in 2014 and 2015. The amount and timing with optimal N rate (ONR) were designed to close the maize yield gap based on the N requirement. Grain yield using the ONR treatments averaged 13.8 Mg ha−1 during 2014 and 2015, which was 90% of the yield potential simulated by the Hybrid-Maize Model. When N treatment was less than the ONR (70% ONR), grain yield decreased from 13.8 to 11.6 Mg ha−1. When additional N fertilizer (130% ONR) was applied, no gain in yield was achieved, but N losses increased significantly from 65 to 121 kg N ha−1. Grain yield was significantly lower in the farmers' typical N practice treatment than that in the ONR treatment. Although 30% more N was applied with farmers' practice, the lowest N use efficiency and greatest N losses were observed. In conclusion, DIPM with optimal N management increased yield potential with high N use efficiency and low N losses in a water-limited region.