Shifts in cultivar and planting date have regulated rice growth duration under climate warming in China since the early 1980s

Abstract

Climate warming accelerates crop development and shortens growth duration. The adoption of new cultivars and changes in planting date may either retard or amplify this acceleration. However, the extent to which the cultivar and planting date shifts have impacted rice growth duration under climate warming remains largely unknown. Using an up-to-date data series from 82 agro-meteorological stations in China where rice phenology was observed from 1981 to 2012, we quantified the impacts of climate warming, cultivar and planting date shifts on rice growth duration based on a degree-days calculation. The results indicate that climate warming shortened the growth duration length (GDL) between emergence and maturity at rates of 4.2±0.7 (mean±SE), 1.8±0.3 and 3.9±0.5days 10-yr−1 for single, early and late rice. GDL shortening was more pronounced in the vegetative phase than in the reproductive phase for single and early rice, but it was opposite for late rice system. Cultivar shifts prolonged the GDL at rates of 6.1±1.0 and 1.7±0.6days 10-yr−1 for single and early rice but induced GDL shortening of 4.1±1.6days 10-yr−1 for late rice. The effect of planting date shifts (advanced or delayed) on GDL change was variable and depended on the rice cropping system. On average, climate warming accelerated crop development, with a relative contribution to GDL changes of −40% in single rice, −45% in early rice, and −35% in late rice. Cultivar shifts compensated for the GDL shortening induced by climate warming in single and early rice with the relative contribution of 58% and 44%, respectively, but accelerated crop development in late rice with a contribution of −37%. Nevertheless, the planting date at two-thirds of the late rice stations was significantly delayed, which retarded the acceleration by 29% in terms of GDL changes.