Evaluation of production capacity for rice-rapeseed cropping system in China

Context or problem: Rice-rapeseed cropping system (hereafter as rice-rapeseed system), as a major cropping system in the Yangtze River Valley (YRV) in China, plays an important role in national food and edible oil se-curity. However, the production capacity of this system remains largely unknown.Objective or research question: We evaluated the yield gap (Yg), energy gap (Eg), and production gap (Pg) of rice -rapeseed system. Regions with largest exploitable Pg were determined and possible scenarios were further analyzed for the evaluation of self-sufficiency rate (SSR) in the next decade. Methods: This study followed Global Yield Gap Atlas (GYGA) protocol (www.yieldgap.org) according to a bottom-up upscaling method with well-calibrated crop models to evaluate Yg, Eg, and Pg from reference weather stations to regions and national levels based on detailed database of daily weather, soil, crop management practices, and high-yielding experiments. Possible scenarios for the assessment of SSR were conducted further for rapeseed in the system.Results: The relative Eg of the system of 42% was mainly affected by the larger relative Yg of 50% in rapeseed rather than that of 37% in rice. By Yg closure to 80% of Yp, a Pg was 8.54 million tons (Mt) for rice and 5.31 Mt for rapeseed in the system. Among the major planting provinces, Anhui had the largest Pg in rice, and Hunan had the largest Pg in rapeseed. As SSR in rice is high in China, we further evaluated rapeseed SSR in the system. We found that SSR in rapeseed was 79% currently and would decrease to 54% in 2031. According to scenario analysis, utilization of 4-39% of current winter fallow fields in YRV was important besides Yg closure for the system to reach a feasible SSR of 80% in the next decade.Conclusions: Large room existed in rice-rapeseed system for further yield increase, especially for rapeseed in the system. Partially utilization of winter fallow fields in YRV is promising to ensure system SSR in the next decade. Implications and significance: This study has evaluated the Yg, Eg, and Pg for rice-rapeseed system, located the regions with large production capacity, and explored feasible strategies to increase rapeseed production and ensure high-level SSR in YRV.