Enhancing water and cropping productivity through Integrated System of Rice Intensification (ISRI) with aquacultureand horticulture under rainfed conditions

Abstract

The System of Rice Intensification (SRI), based on modifications in the management practices for rice cultivation, is being utilized in many countries, although not without some controversy. One reason cited for non-adoption or dis-adoption of SRI is difficulties with water management under rainfed conditions with unreliable or aberrant rainfall distribution, which causes either flooding or long dry spells, or both. These constraints could be dealt with by tapping groundwater resources or by capture and use of rainwater-runoff and/or by diversification of the farming system. A 2-year field experiment was conducted in Odisha, India to evaluate SRI under rainfed conditions and also to explore options for enhancing the economic productivity of land and water under such conditions.Four rice cropping systems were evaluated: (i) conventional rice cultivation under rainfed conditions,(ii) SRI methods as adapted to rainfed cultivation, (iii) rainfed SRI methods with drainage facilities and supplementary pump-irrigation, and (iv) integrated SRI (ISRI) where rainwater runoff was harvested and stored for aquaculture and horticulture crops while also providing supplementary irrigation for the rice crop.The rice crop grown with adapted SRI practices under rainfed condition showed significant improvements in the plants’ morphology and physiology. Phenotypic changes included: greater plant height and tillering, more number of leaves, and expanded root systems. These changes were accompanied by changes in plants’ physiological functions like greater xylem exudation rate and more light interception by the canopy, increased chlorophyll content in the leaves, and higher light utilization and photosynthetic rates during flowering. These factors were responsible for improved yield-contributing characteristics and for higher grain yield (52%) as compared with crops grown by conventional production methods.Comparing yield from rainfed conventional vs. SRI methods between drought and normal-rainfall years indicated that the latter methods are more drought-tolerant and productive; greatly expanded and active root systems with SRI have been important contributing factors.Introducing drainage and supplementary irrigation improved both the grain yield (by 29%) and water-productivity for rainfed SRI. Further, integrating aquaculture and horticulture with SRI management and rainwater harvesting increased the rice yield further (by 8%) and the net water productivity. This integrated system was found to raise the net income per unit of water by more than 60-fold compared to conventional rainfed rice cultivation. This option looks promising for improving food security for small holders under erratic or diminished rainfall conditions.