Spatio-temporal distribution of sugarcane potential yields and yield gaps in Southern China

The sustainability and production capacity of sugarcane (Saccharum officinarum (L.)) in Southern China is essential to ensure sugar security in China, yet potential crop yield and yield gap (the difference between actual and potential crop yield) of sugarcane is poorly known. In this study, the sugarcane growth and development model, QCANE, was validated for sugarcane phenology, stalk height, and yields, then used to simulate potential yields and yield gaps of sugarcane in Southern Chine (SC) between 1970 and 2014. Simulated potential yields decreased as longitude and latitude increased, driven by spatial variation in solar radiation and maximum temperature. The gap between potential and water-limited yields was noticeably larger in Yunnan province because of the prevalence of seasonal water deficiency. However, nitrogen stress was the dominant driver of the yield gap, given the abundant precipitation in SC. Across SC, large variation in the yield gap between water-and-nitrogen limited yields and on-farm yields was observed for different counties, a difference that was usually larger than the local yield gap. Averaged across SC, on-farm sugarcane yields were only 27% of potential yields, 31% of water-limited yields, and 52% of nitrogen-limited yields. This result highlights considerable potential to significantly increase sugarcane production by improving varieties, government support, effective management measures such as fertilization, irrigation, and mechanization.