Rice yields decline with higher night temperature from global warming

Abstract

The impact of projected global warming on crop yields has been evaluated by indirect methods using simulation models. Direct studies on the effects of observed climate change on crop growth and yield could provide more accurate information for assessing the impact of climate change on crop production. We analyzed weather data at the International Rice Research Institute Farm from 1979 to 2003 to examine temperature trends and the relationship between rice yield and temperature by using data from irrigated field experiments conducted at the International Rice Research Institute Farm from 1992 to 2003. Here we report that annual mean maximum and minimum temperatures have increased by 0.35 degrees C and 1.13 degrees C, respectively, for the period 1979-2003 and a close linkage between rice grain yield and mean minimum temperature during the dry cropping season (January to April). Grain yield declined by 10% for each 1 degrees C increase in growing-season minimum temperature in the dry season, whereas the effect of maximum temperature on crop yield was insignificant. This report provides a direct evidence of decreased rice yields from increased nighttime temperature associated with global warming.

Fig. 1.

Trends in maximum and minimum temperatures and radiation from 1979 to 2003 for the whole year (A–C), dry season (January to April) (D–F), and wet season (June to September) (G–I) at the IRRI Farm. Trends (slopes) for the maximum temperature in A, D, and G and radiation in F are not statistically significant at the P < 0.05 probability level according to the Student's t test.

Fig. 2.

The relationship between rice-yield attributes (grain yield, above-ground total biomass, and spikelets per m²) and growing-season mean maximum temperature (A–C), minimum temperature (D–F), or radiation (G–I). Yield-attribute data were obtained from irrigated field experiments in which crop-management practices were optimized to achieve the highest possible yields from rice cultivar IR72 at the IRRI Farm in the dry seasons from 1992 to 2003. Growing-season mean maximum and minimum temperatures and radiation were calculated from daily values for the entire growing season from transplanting to harvest.