Rice Physiology, Yield and Water Productivity Improvements Through Modifying Cultivation Practices and Water Management

The Green Revolution raised the yields of rice and other cereals by using semi-dwarf cultivars, large quantities of water, chemical fertilizers, and herbicides/pesticides. This technology collaterally affected soil health, water scarcity, air/water pollution, and the energy-nexus. Now, to feed the global population, rice yields need to increase using less water and other inputs in a sustainable, environment-friendly way under climate-change scenario. Research from >40 countries shows that the System of Rice Intensification (SRI) offers advantages like yield enhancement, water saving, greater income, reduced GHG emissions, and climate-change resilience. SRI recommends keeping rice fields moist but unflooded during the crop's vegetative stage and then maintaining shallow flooding during its reproductive stage. However, no evaluation is available on how flooding paddy fields continuously vs. alternately (AWD) during the post-vegetative stage may influence SRI crops' physiology, root growth, grain yield, and water productivity. Field experiments were conducted at ICAR-Indian Institute for Water Management to evaluate SRI vs. conventional management practice (CMP) under different water management treatments, during the vegetative stage [continuous flooding (CF) vs. AWD], and then in post-vegetative stage: CF vs. AWD either 1-day after disappearance (DAD) of ponded water, 3-DAD, or 5-DAD. Compared to CMP practices, SRI significantly improved plants' root growth and xylem exudation rate, leaf area index, and light interception, plus photosynthesis rate during grain-filling, resulting in 58% higher grain yield with 16% less water. Across all water management treatments, significantly more grain was produced per unit of water applied under SRI management (6.3 kg/ha-mm) compared to CMP (3.3 kg grain/ha-mm). Highest grain yield (6.2 t/ha) and greatest water productivity (6.7 kg/ha-mm) were obtained with SRI methods plus AWD @ 3-DAD post-vegetative irrigation. With CMP, highest grain yield (4.1 t/ha) and water productivity (3.5 kg/ha-mm) were with AWD @ 1-DAD irrigation. Differences measured in plants' response to modified management practices (SRI) and alternative irrigation schedules indicated how phenotypic and physiological performances for a given genotype can be improved. Combining improved changes in crop and water management can improve water productivity as well as grain yield to feed globe in a sustainable way.