Reducing nitrogen and regulating density enable sustainable production of rice–wheat rotation system in the lower reaches of Yangtze River of China: a two-year rotation study

BACKGROUND: In rice (Oryza sativa L.)–wheat (Triticum aestivum L.) rotation systems, sustaining annual crop productivity under reduced nitrogen and regulated planting density, while simultaneously improving grain yield and resource-use efficiency, remains a major challenge.

RESULTS: In this study, the indica-japonica hybrid rice Yongyou 2640 and the spring wheat Yangmai 20 were field-grown from 2017 to 2019 for 3 years with four cultivation practices: no nitrogen application; local conventional practice (LCP); reducing nitrogen; and reducing nitrogen and regulating density (RNRD). We characterized the grain yield, resource use efficiency, economic benefit, and major aboveground agronomic and physiological traits of rice and wheat in the rice–wheat rotation system in the lower reaches of the Yangtze River in China. The RNRD synchronously increased annual grain yield and resource use efficiency (nitrogen and radiation use efficiency) of rice and wheat compared with LCP. The economic benefit was also improved under RNRD. The high grain yield and resource use efficiency of rice and wheat mainly benefit from the increased total number of spikelets especially for rice, percentage of productive tillers, leaf area index, grain–leaf ratio, light interception rate, flag leaf photosynthetic rate, and aboveground dry matter accumulation.

CONCLUSION: The sustainable production goal of annual high yield and high resource use efficiency of crops could be achieved through adopting the effective and low-cost cultivation practices containing appropriate N application and planting density in the rice–wheat rotation system in the lower reaches of Yangtze River of China.