Impacts of Cultivation Practices and Water Management in the Post-Vegetative Stage on Rice Grain Yield and Water Productivity.

Achieving higher productivity in irrigated rice production is becoming ever-more important with growing water scarcity. The System of Rice Intensification (SRI), a modified cultivation methodology, recommends keeping rice fields moist but unflooded during the crop’s vegetative stage, usually with alternate-wetting-and-drying; then maintaining shallow flooding during the post-vegetative stage of crop growth. No evidence-based evaluation is available on the impact of flooding paddy-fields continuously vs. alternately during post-vegetative stage under SRI management, and how this could influence the crops’ physiology, their root growth, grain yield, and water productivity.

Field experiments were conducted to investigate the impacts of different water management treatments during post-vegetative stage: continuous flooding (CF) compared with irrigation at 1-DAD (days after disappearance of ponded water), 3-DAD, and 5-DAD, under two alternative crop management systems, namely, SRI and conventional transplanting system (CTS). During their preceding vegetative stage of crop growth, CTS plots were kept continuously flooded, while SRI plots received irrigation 3-DAD.

Compared to CTS methods, SRI practices significantly improved plants’ root growth and xylem exudation; LAI and light interception by crop canopy; plus leaf-chlorophyll content and photosynthesis rate. These factors resulted in significant increases in higher yield components and grain yield with SRI methods. In the trials, SRI produced 58% higher yield with 16% less water than achieved with CTS.

Across all water management treatments, significantly more grain was produced per unit-quantity of water applied with SRI management (6.3 kg/ha-mm) compared to CTS (3.3 kg/ha-mm). The highest grain yield under SRI (6.2 t/ha) and greatest water productivity (6.7 kg/ha-mm) occurred with 3-DAD treatment, while with CTS, highest grain yield (4.1 t/ha) and most water productivity (3.5 kg/ha-mm) were with 1-DAD irrigation. It is concluded that combining changes in crop and water management can improve water productivity as well as grain yield.