Effect of high water temperature during vegetative growth on rice growth and yield under a cool climate

Global warming is likely to increase spring temperatures in regions with a cool climate. To examine the effects of this change on rice productivity, we exposed rice plants to a higher (by +2.7 to +2.8 °C) water temperature (Tw) during the vegetative growth period (for 35–50 days) under three levels of N fertilization. High Tw during vegetative growth made the heading stage occur 4–7 days earlier for all levels of N fertilization in both years. The crop growth rate during the treatment period was greatly enhanced by high Tw: by 51–82% in 2008 and by 49–62% in 2009. There was no Tw × N fertilizer interaction. This increased growth was associated with increased leaf expansion and increased canopy radiation capture rather than with increased radiation-use efficiency. However, the positive effect decreased during subsequent growth stages under all levels of N fertilization, leading to no significant differences in total biomass at maturity. High Tw during vegetative growth greatly reduced SPAD values during the grain-filling stage compared with SPAD values in the control Tw treatment, for all levels of N fertilization, and decreased leaf photosynthesis during the mid-grain filling stage. Grain yield was not significantly affected by high Tw at any N fertilizer level or in either year.

Research highlights▶ High Tw during vegetative growth strongly enhanced biomass production in rice, but the positive effect decreased during subsequent growth stages under all levels of N fertilization, leading to no significant differences in total biomass and grain yield at maturity.