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

Abstract

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 ( T w) during the vegetative growth period (for 35–50 days) under three levels of N fertilization. High T w 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 T w: by 51–82% in 2008 and by 49–62% in 2009. There was no T w × 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 T w during vegetative growth greatly reduced SPAD values during the grain-filling stage compared with SPAD values in the control T w 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 T w at any N fertilizer level or in either year.