Rice root growth, photosynthesis, yield and water productivity improvements through modifying cultivation practices and water management

Abstract

Achieving higher productivity in irrigated rice production is becoming ever-more important. A modified rice-cultivation method, the System of Rice Intensification (SRI), recommends keeping rice fields moist but unflooded during the crop’s vegetative stage, usually with alternate-wetting-and-drying (AWD), then maintaining shallow flooding during the post-vegetative stage of crop growth. However, no evidence is available on how flooding paddy fields continuously vs. alternately during the post-vegetative stage under SRI might influence the crops’ physiology, root growth, grain yield, and water productivity. Field experiments were conducted to investigate the impacts of two alternative crop management systems, namely, SRI and conventional management practice (CMP) under different water management treatments during the vegetative stage [continuous flooding (CF) vs. AWD] and then during post-vegetative stage: CF vs. AWD @ 1-DAD (days after disappearance of ponded water), 3-DAD or 5-DAD. SRI practices, compared to CMP methods, significantly improved plants’ root growth and xylem exudation rate, leaf area index and light interception by the crop canopy, plus photosynthesis rate at the grain-filling stage, resulting in higher grain yield. Overall, this modified method of rice crop management produced 58% higher grain yield with 16% less water. Across all water management treatments, significantly more grain was produced per unit of water applied with SRI management (6.3 kg ha/mm) compared to CMP (3.3 kg grain ha/mm). The highest grain yield with SRI (6.2 t/ha), and the greatest water productivity (6.7 kg ha/mm) were obtained with SRI and 3-DAD post-vegetative irrigation. With CMP, highest grain yield (4.1 t/ha) and water productivity (3.5 kg ha/mm) were with 1-DAD irrigation. Differences measured in plants’ response to modified management practices and alternative irrigation schedules indicated how phenotypic and physiological performances can be improved for a given genotype. Combining changes in crop and water management can improve water productivity as well as grain yield.