Impact of coated urea combined with conventional urea on the yield, nitrogen use efficiency, and soil residual nitrate of summer maize

The present study was conducted to assess the effects of single basal application of blended fertilizer (coated urea blended with conventional urea) on summer maize yield, nitrogen use efficiency (NUE), economic returns, and residual soil nitrate, which could provide technical support for simplified cultivation and N application reduction as well as efficiency improvement for summer maize. A field experiment was designed to investigate the yield and N uptake of summer maize and soil inorganic N dynamics, and the summer maize cultivar Fuyou 9 was used as the material. The experiment included six treatments, namely no N fertilizer (CK), conventional N application (CON), 10% N rate reduction with a 30% ratio of coated urea (90N-30C), 10% N rate reduction with a 50% ratio of coated urea (90N-50C), 20% N rate reduction with a 30% ratio of coated urea (80N-30C), and 20% N rate reduction with a 50% ratio of coated urea (80N-50C). Showed the release pattern of coated urea showed a parabolic curve, and the release duration was 81 d (80% cumulative N release) under field conditions. In comparison with CON, the summer maize yield and NUE of blended fertilizer with basal application were increased by 2.85%~20.87% and 19.1~25.3 percent point, respectively. Compared with CON, the economic return of summer maize with blended fertilizer was increased by 1 000~4 484 yuan·hm-2. In comparison with conventional urea, the soil residual nitrate at 100~200 cm soil depth with blended fertilizer was reduced by 35.1%~56.6%, therefore, the risk of nitrate leaching was significantly decreased. Compared with conventional fertilization, single basal application of blended fertilizer with a 10%~20% N rate reduction increased the summer maize yield, NUE, and economic returns, and decreased the nitrate residue in the deeper soil layer, which mitigated the risk of environmental pollution. In summary, 90N-30C was superior considering the summer maize yield, NUE, economic returns, and residual soil nitrate.