SRI METHODOLOGIES
SRI is based upon a set of principles and practices for increasing the productivity of irrigated rice by changing the management of plants, soil, water and nutrients.
The practices described below contribute to both more fertile soil and healthier plants supported by greater root growth and the nurturing of soil microbial abundance and diversity. SRI practices and concepts, which are based on a number of agroecological principles with good scientific foundations, have also been successfully adapted to upland rice and to other crops such as wheat, finger millet, and sugarcane.
Basic SRI Management Practices
Rice plants -- Seedlings are transplanted:
- very young › usually just 8-12 days old, with just two small leaves
- carefully and quickly › to have minimum trauma to the roots
- singly › only one per hill instead of 3-4 together to avoid root competition
- widely spaced › to encourage greater root and canopy growth
- in a square grid pattern › 25x25 cm or wider in good quality soil
Some farmers are experimenting with direct-seeding adaptations of SRI principles, and even with mechanized transplanting. So these recommendations concern how to transplant rice most productively if transplanting is done. SRI is not a recipe of precise things to do, but rather a menu for bringing out rice plants' potential.
- Soil › This is kept moist but well-drained and aerobic, with good structure and enough organic matter to support increased biological activity. The quality and health of the soil is the key to best production.
- Water › Only a minimum of water is applied during the vegetative growth period, and thereafter only a thin layer of water is maintained on the field during flowering and grain-filling. Alternatively, to save labor time, some farmers flood and drain (dry) their fields in 3-5 day cycles with good results. Best water management practices depend on soil type, labor availability and other factors, so farmers should experiment on how best to apply the principle of having moist but well-drained soil while their rice plants are growing.
- Nutrients › Soil nutrient supplies should be augmented, preferably with compost, made from any available biomass. Better quality compost such as with manure can give additional yield advantages. Chemical fertilizer can be used and gives better results than with no nutrient amendments, but it does not enhance soil structure and microbial communities in the rhizosphere as applying organic matter accomplishes. At least initially, nutrient amendments may not be necessary to achieve higher yields with the other SRI practices, but it is desirable to build up soil fertility over time. Root exudation, greater with SRI, enhances soil fertility.
- Weeds › Since weeds become a problem in fields that are not kept flooded, weeding is necessary several times, starting 10-12 days after transplanting, and if possible, every 10-12 days until before the canopy closes. Using a rotary hoe -- a simple, inexpensive, mechanical push-weeder -- has the advantage of aerating the soil at the same time that weeds are eliminated. (They are left in the soil to decompose so their nutrients are not lost.) Additional weedings beyond two can increase yield more than enough under most conditions to more than justify the added labor costs. (See WASSAN Weeder Compendium, our playlist for weeders (manual and mechanized) and short weeder slide presentation for more on weeders).
For more details, see some of the "instructional materials" on SRI that are available in English, French, Nepali, Spanish, Thailand other languages. "Instructional materials" is put in quotation marks because SRI is not conceived of and promoted as a technology with a fixed set of practices; it is not a "package" to be adopted in a fixed way. There are a number of variations in the practices that should be considered and evaluated under field conditions. The use of SRI concepts and principles continues to evolve as more experience is gained in a variety of agroecological settings.
