Effects of Planting Density, Levels, and Forms of Nitrogen Application on the Yield and Nitrogen Utilization of Wheat following Rice in East China

A major challenge is to achieve the goal of synergistically increasing grain yield and nitrogen use efficiency in wheat production. Many studies have focused on one aspect of cultivation such as fertilizer management, suitable planting density, and straw returning. However, there are few studies on the effect of integrated cultivation practices on yield and nitrogen absorption and utilization of wheat. A field experiment to investigate the characteristics was conducted across two years using Yangmai 16 and Yangmai 20 with five cultivation practices including nitrogen blank area (NB), local practices (LP), nitrogen reduction (NR), planting density reduction and nitrogen reduction (DN), and organic fertilizer (OF). As compared with LP, the DN treatment improved the yield (+4.54%), recovery efficiency of N fertilizer (+5.59%), N partial factor productivity (+15.28%), agronomic N use efficiency (+21.43%), physiological N use efficiency (+14.90%), and nitrogen harvest index (+6.45%). All previous indices were increased by 16.84%, 28.18%, 19.59%, 45.81%, 13.96%, and 3.37% under the OF treatment, as compared with LP. The DN and OF significantly improved nitrogen use efficiency, photosynthetic characteristics, dry matter accumulation, root total and active absorbing surface area, root oxidation activity, nitrogen accumulation, nitrogen harvest index, and nitrogen transportation in various organs. The results suggest that integrated cultivation practices are beneficial to achieve high yield and high nitrogen use efficiency through improving the agronomic performance and root physiological characteristics.