The Science behind the System of Rice Intensification (SRI)

Abstract

Rice is life for more than half of humanity. It is the grain that has shaped the cultures, diets, and economies of billions of people in the world. Food security in the world is challenged by increasing food demand and threatened by declining water availability. Exploring ways to produce more rice with less water is essential for food security. The System of Rice Intensification (SRI), a new method of rice cultivation, offers an opportunity for reducing water demand accompanied by yield enhancement of rice. SRI management involves many departures from the methods conventionally recommended for rice cultivation. It proposes the use of single young seedlings, drastically reduced plant densities, keeping fields unflooded, use of a mechanical weeder which also aerates the soil, and enhanced soil organic matter. These practices have the aim of providing optimal growth conditions for the plant, to get better performance in terms of yield and resource productivity. Field experiments were conducted to investigate whether practices of the System of Rice Intensification (SRI), could improve rice plants’ morphology and physiology and what would be their impact on resulting crop performance, compared with currently recommended scientific management practices (SMP). With SRI practices, grain yield was increased by 48% in these trials at the same time, there was average water saving of 22% compared with inundated SMP rice. Water productivity with SRI management practices was almost doubled (0.68 g l-1) compared to SMP (0.36 g l-1). Significant improvements were observed in the morphology of SRI plants in terms of root growth, plant/culm height, tiller number per hill, tiller perimeter, leaf size and number, leaf area index (LAI), specific leaf weight (SLW), and open canopy structure. These phenotypic improvements of the SRI crop were accompanied by physiological changes: greater xylem exudation rate, crop growth rate, mean leaf elongation rate (LER), and higher light interception by the canopy compared to rice plants grown under SMP. SRI plants showed delayed leaf senescence and greater light utilization, and they maintained higher photosynthetic rates during reproductive and grain-filling stages. This was responsible for improvement in yield-contributing characteristics and higher grain yield than from flooded rice with SMP. We conclude that SRI practices improve rice plants’ morphology, and this benefits physiological processes that result in higher grain yield and water productivity.