Effect of Nitrogen Application Rate on Grain Yield, Dry Matter and Nitrogen Accumulation and Remobilization in a Winter Wheat-Fresh Maize Cropping System

Abstract

Three-harvest in two years is a traditional farming system in the Jinzhong Basin of Shanxi Province of the eastern Loess Plateau in China. Recently, an innovative farming system of winter wheat-fresh maize with two-harvest per year, making full use of temperature and light resources, is proposed. However, there is little known of the optimal nitrogen application rate for the innovative farming system to increase crop yield and improve ecological environment. In current study, six nitrogen application rates were carried out, consisting of winter wheat/fresh maize season 0/0 kg·ha-1 (N0, Control), 75/75 kg·ha-1 (N75), 150/150 kg·ha-1 (N150), 225/225 kg·ha-1 (N225), 300/300 kg·ha-1 (N300) and 375/375 kg·ha-1 (N375). The grain yield, dry matter and nitrogen accumulation and remobilization were analyzed to determine the optimal nitrogen application rate in the winter wheat-fresh maize cropping system in the Jinzhong Basin. The results showed that in the winter wheat and fresh maize season, compared with the N0, N75 and N375 treatments, total dry matter accumulation at winter wheat maturity and fresh maize harvesting increased significantly by 82.9%-94.5% and 26.1%-197.1%, respectively, and dry matter remobilization in leaves and stem+sheath (+tassel) increased significantly under the N150 treatment. Total nitrogen accumulations under the N150, N225 and N300 treatments increased significantly by 58.2%-162.9% and 55.7%-301.7% compared with those under the N0 and N75 treatments, respectively. Nitrogen remobilization in the kernel and stem+sheath (+tassel) under the N150 treatment increased significantly compared with the N0 and N75 treatments. In addition, nitrogen partial factor productivity of winter wheat and fresh maize under the N75 and N150 treatments increased significantly by 36.7%-534.1% and 45.2%-390.4% compared with the other nitrogen treatments, respectively, and nitrogen uptake efficiency also increased significantly by 79.1%-321.4% and 58.3%-239.5%, respectively. The yield of winter wheat and fresh maize under the N225 treatment was the highest, which significantly increased by 54.1% and 71.6% compared with that under the N0 treatment, respectively. In summary, nitrogen application rates of 150-225/150-225 kg·ha-1can be potential recommended use amounts with higher crop yield and nitrogen use efficiency in winter wheat-fresh maize cropping system in the Jinzhong Basin.