Timing of rice maturity in China is affected more by transplanting date than by climate change

The phenological development of rice is a critical element affecting grain yield. The phenophases of rice development from transplanting through heading to maturity have often been linked to climatic factors, such as temperature and solar radiation. In contrast, the effects of physiological processes on the timing of rice maturity have not been well investigated. In this study, we examined shifts in the timing of transplanting, heading, and maturity of single, early, and late rice in China during the period 1991-2012; we used in situ records assembled at 113 agricultural stations, and explored the correlations between changes in the timing of phenological events and (i) climatic and (ii) physiological factors. We detected a significant warming trend through whole growing seasons (from transplanting to maturity) for all three rice varieties; this trend had negative impacts on the dates of maturity. The durations of the growing seasons over the period were extended by 4.1. ±. 2.0, 1.8. ±. 2.9, and 2.2. ±. 1.9 days for single, early, and late rice, respectively. However, for single rice, the extension was related to delayed dates of transplanting and maturity, whereas for early and late rice, it was attributed to advances in the dates of transplanting and maturity. The timing of maturity in all rice types was most closely related to transplantation and heading dates; climatic factors were of secondary importance. We hypothesize that internal regulation processes operating via carbohydrate content or leaf/cell longevities likely influence rice phenological processes through hormonal mechanisms. Early-season phenological events clearly influence the timing of plant maturity; the dates of early season events are shifting. Therefore, current protocols for global and regional crop modeling that use fixed planting dates are unlikely to accurately account for the impacts of climate change on croplands.