[Differences of wheat yield and economic benefits between soybean-wheat and rice-wheat cropping under different nitrogen fertilization patterns in Jianghan Plain, China].

We analyzed winter wheat yield and growth pattern of soybean-wheat and rice-wheat rotation systems in response to different nitrogen fertilization patterns with the aim to provide theoretical basis for narrowing the wheat yield gap between the two rotations in Jianghan Plain. Field experiments were conducted with three treatments, control without nitrogen, traditional nitrogen management (70% nitrogen as basal and 30% nitrogen as topdressing at overwintering), and improved nitrogen management (one third of N was applied at sowing, wintering and jointing, respectively). The growth pattern, grain yield, yield components, fertilizer use-efficiency and economic benefit under the different nitrogen fertilization patterns were examined. Results showed that grain yield was significantly affected by both nitrogen fertilization pattern and crop rotation. Grain yield under improved nitrogen treatment was significantly higher, with the yield gap being 920 kg·hm in soybean-wheat rotation and 2195 kg·hm in rice-wheat rotation. Traditional nitrogen management showed advantage in establishing winter and spring population. Dry matter accumulation was higher under improved nitrogen treatment than traditional treatment with 5%-31% and 14%-28% increases for soybean-wheat and rice-wheat rotations, respectively. The higher yield in the soybean-wheat rotation was due to greater panicle numbers, higher percentage of tiller ears, and dry matter accumulation. The rice-wheat rotation under improved nitrogen showed a significant increase in grain yield compared with soybean-wheat rotation. This result indicated that yield gap between the two crop rotations could be narrowed through suitable nitrogen management. Grain weight after anthesis showed "slow-fast-medium" in soybean-wheat rotation and "medium-fast-slow" in rice-wheat rotation. Nitrogen use efficiency and net benefit of wheat season were higher in rice-wheat system. Overall, the rice-wheat system showed obvious advantages in population structure, dry matter accumulation, grain yield and benefit under improved nitrogen pattern, which was the optimum pattern for both wheat yield and benefit in Jianghan Plain.