Effects of Sowing Date, Density and Nitrogen Application Amount on Nitrogen Utilization Rate of Guangmingmai 1 Grown in Rice-Wheat System

Improvement of utilization rate of nitrogen fertilizer (NUR) is one of research focuses in wheat. In a two-year field experiment, the NUR of wheat variety Guangmingmai 1 in the wheat-rice rotation system in response to sowing date (S), density (D), and nitrogen application rate (N) was studied using a mathematical model based on quadratic regression rotation-orthogonal combination design. Among the three factors, nitrogen application rate had the greatest effects on NUR, followed by sowing date and density. Several S+D+N combinations resulted in high yield and high NUR under the experimental conditions. The highest yield level (6800-7200 kg ha -1 ) was obtained in the combination of S between October 28 and November 2, D between 1.6 and 1.8 million plants per hectare, and N at 200 kg ha -1 . Simultaneously, the NUR was higher than 42.0% (the maximum was 44.8%) with a credibility larger than 95%. At the yield level of 6200-7000 kg ha -1 and NUR higher than 41.0%, the optimal S, D and N were 21-27 October, 1.2-1.5 million plants per hectare and 190-225 kg ha -1 , respectively. At the yield level of 5900-7250 kg ha -1 and NUR higher than 39.0%, the agronomic practices were recommended to be S between November 3 and November 11, D be- tween 2.1 and 2.4 million plants per hectare, and N between 190 and 210 kg ha -1 .