Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 18, 1996
Publication Date: N/A
Interpretive Summary: Atmospheric carbon dioxide (CO2) concentration is rising. One consequence is that rainfall patterns may change. Much of the world's irrigated and rainfed rice yields could be decreased if drought becomes more prevalent. Scientists in the Crop Genetic and Environmental Research Unit in Gainesville, FL conducted an experiment in paddy culture rice in which water was withheld and drought imposed at critical stages of growth: (1) at the time that the seed heads were just beginning to initiate in the stems; (2) at the time of flowering, and (3) at both stages of growth. Photosynthesis was decreased only when drought became severe; at that point the plants were rewatered. Grain yields and growth were reduced sharply when drought occurred only at the flowering stages of growth. The plants withstood drought better at earlier stages of growth. Thus, rice farmers would need to plan to have adequate irrigation water at the flowering stage if at all possible, or to adjust planting dates for the best probability of adequate rainfall shortly before flowering of the rice crop.
Doubling of atmospheric carbon dioxide (CO2) is likely to cause shifts in precipitation patterns. Drought is a major limitation for crop yield and is common in rainfed rice production systems. This study was conducted to determine the growth and grain yield responses of rice to drought under CO2 enrichment. Rice (cv. IR-72) was grown in eight naturally-sunlit chambers in CO2 concentrations of 350 and 700 micromole CO2 per mole air. In both CO2 exposures, water management treatments were: continuously flooded (CF) controls, flood water removed and drought imposed at panicle initiation (PI), anthesis (ANT), and both stages of growth (PI & ANT). The CO2 enrichment increased growth, panicles per plant, and grain yield. Drought accelerated leaf senescence, reduced leaf area and above ground biomass, and delayed crop ontogeny. The CO2 enrichment allowed 1 to 2 days more growth during drought cycles. Grain yields of PI and PI & ANT were similar to CF while ANT sharply reduced growth, grain yield, and individual grain mass. Future global increases in CO2 should promote rice growth and yield while decreasing water use about 10%, and thus increasing drought avoidance.