System of Rice Intensification

The System of Rice Intensification (SRI) is a method of managing rice plants, soil, water and nutrients to promote stronger roots and more productive tillers. It is not a rice variety or a rigid input package; its central principle is to grow widely spaced, young plants in moist, aerated soil rather than keeping the field continuously submerged.

Principal features

• Young seedlings are transplanted early, before prolonged nursery growth restricts their development.
• A single seedling is generally planted per hill instead of a clump of seedlings.
• Seedlings are handled carefully and planted shallow to minimise root injury and transplanting shock.
• Plants are arranged at wider, regular spacing, commonly in a square pattern, to improve access to sunlight, nutrients and air.
• The soil is kept moist through intermittent irrigation and periodic drying rather than continuous flooding.
• Mechanical weeding between rows controls weeds while also aerating the surface soil.
• Organic matter is encouraged to improve soil biological activity and structure, although SRI does not necessarily exclude mineral fertilisers.
• The practices are adapted to local soil, climate, water availability and rice variety rather than applied as an inflexible package.

Difference from continuously flooded paddy cultivation

The main distinction lies in plant density and water management, supported by differences in transplanting and weed control.

• Continuously flooded cultivation maintains standing water for much of the crop period, whereas SRI avoids prolonged submergence and uses intermittent irrigation.
• Conventional transplanting commonly places several seedlings together, whereas SRI generally uses one seedling per hill.
• Conventional systems often use relatively older seedlings and closer spacing, whereas SRI favours younger seedlings and wider, regular spacing.
• Flooding suppresses many weeds, whereas the non-flooded intervals under SRI require timely weeding, often with a mechanical weeder.
• SRI normally requires less seed and irrigation water, but timely field operations and careful management are more important.
• SRI seeks to maintain an aerated root zone, while continuous flooding creates predominantly anaerobic soil conditions.

Environmental and agronomic significance

• Intermittent soil aeration can reduce methane formation because methane-producing microorganisms thrive under anaerobic flooded conditions.
• Lower irrigation demand can improve water-use efficiency, especially where water is scarce or pumping consumes energy.
• Mechanical weeding and organic matter management can improve soil aeration and biological activity.
• Yield and emission outcomes are not automatic; they vary with soil, climate, variety, nutrient management and the quality of field operations.

How UPSC asks this