Definition of System of Rice Intensification (SRI):
System of rice intensification (SRI) concept is an alternate to the existing practises where fields are kept wet, not flooded with water. This system seems to be promising to overcome the shortage of water in irrigated rice The SRI appear to be a viable alternate for rice cultivation that saves expensive inputs, improves soil health besides optimum water-use efficiency.
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Origin:
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The system of rice intensification originated in Madagascar and was first synthesized in 1983 by Fr. Henri de Laulanie. Under the drought conditions of that year.
Significance:
There are three basic concepts constituting system of rice intensification. They are to be applied with adjustments in specific practices like spacing and timing as appropriate to local conditions. Transplanting the seedlings while still young, <15-days-old, i.e., prior to the start of the 4th phyllochron of growth. This preserves plants potential for tillering and root growth that is reduced by transpjanting later. Direct seeding is an option, however, since what is important is that plant roots should not be traumatized after they start their growth trajectory, on or about the 15th day. Careful transplanting promotes rapid resumption of growth.
Wide spacing between plants is maintained with preferably just one plant/hill, and set them out in a square pattern, 25 cm x 25 cm or even wider if soil fertility is good. This gives room for profuse root and tiller growth, achieving ‘the border effect’ throughout the whole field. Another important aspect in SRI is to keep the soil both moist and aerated, at least during the vegetative growth period, so that roots have access to both oxygen and water. Under continuously hypoxic conditions, rice roots degenerate, with as many as 75% become dysfunctional by panicle initiation. Therefore, the aerobic conditions in SRI promote root growth substantially over submerged situations.
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Specific practices include in addition to using young seedlings with still only two leaves, planted singly and widely spaced, frequent weeding, preferably with a rotating hoe that aerates the soil while it prevents weeds growth by churning them into the soil, application of small amounts of water daily, or alternate flooding and drying of fields for 3 to 6-day periods, and providing organic matter to the soil. Organic matter can be any decomposed biomass, including rice straw or weeds, manure or mulch can also be used. Green manures and cover crops are also useful. Correct implementation of the various, interdependent components (SRI practices) requires considerable field experience in which close observation and timeliness are crucial in minimizing labour requirements while maximizing total factor productivity.
Benefits associated with SRI:
1. Greater root growth
2. Increased tillering
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3. Increased grain filling
4. Improved grain quality and higher grain weight
5. Water savings
6. Less lodging
7. Reduced pest and disease attacks
8. Reduced or no need for chemical fertilizers
9. Seed savings
10. No need to purchase new seeds
11. Low cost of production
12. Increased factor productivity and profitability
13. Reduced risks
Conclusion:
Rice yields all over the world have leveled out under the present system of flooded cultivation. We need to be looking for alternatives to existing practices with an open mind. SRI is still evolving and it is hoped that the scientific community will collaborate in further refining the SRI practices and working out the scientific reasons for the reported higher productivity.
Planting young seedlings carefully and at wider spacing gives the plant more time and space for tillering and root growth. Careful water management keeping the field wet and not flooded gives better yield as it supports healthy root growth. This practice should be encouraged everywhere as the whole world is facing water shortages. Weeding rice fields with a rotary weeder helps by churning the soil and incorporating the weed biomass as it aerates the root zone. Therefore, seeing the overall benefits, the SRI needs to be evaluated further and refined to suit the local environments.