|Low-external Input Rice Production (IIRR, 292 p.)|
|Water management/cropping patterns|
A number of strategies exist for farmers to minimize risks and reduce losses in drought-prone and rainfed rice-producing areas. These strategies focus mainly on the following: varietal selection, timing of planting to minimize drought damage, maintenance of water level, cultural practices aimed at conserving water or improving drought resistance and altering the physical farm environment.
1. Varietal selection
· Select drought-tolerant varieties if drought is likely to occur. In general, IRRI found droughttolerant rice varieties to have long, dense and thick roots. Traditional varieties like BE-3, Peta and Intan tolerate some drought but yields are lower than modern varieties. The IRRI varieties IR6, IR46 and IR64 also withstand mild drought although IR36 and IR64 are prone to tungro disease.
· Plant very short-duration varieties to avoid the drought period entirely.
2. Timing of-planting
· Plant the rice such that the vulnerable reproductive stage does not fall during the drought season. This presupposes a regularly occurring drought in a region which the farmers anticipate and plan around.
· Synchronize planting with neighboring farmers to minimize irrigation water wastage.
3. Maintenance of water level
· It is important to provide the crop enough water to induce maximum tillering (formation of stalks) for a good cover (canopy) so that water losses by evaporation would be minimized.
· Water is essential during flowering on from 55-70 days after transplanting of the shortduration varieties. If simultaneous planting is done, 800-1,000 mm of water would be minimum requirement.
· Fields need only be kept moist (not flooded) all the time with a 1-2 mm layer as minimum. Using this strategy gives a 30-50% cut requirements without yield losses.
4. Other cultural practices
· Maintain rice paddy dikes to minimize seepage and clean irrigation ditches regularly.
· Establish good weed control. Most weeds are much more efficient than rice in exploiting soil moisture.
· Supply nitrogen (N) and other fertilizers early. If using less than 30 kg N/ha, apply all of it basally. If applying more than 30 kg N/ha, use the best split (2/3 basal and 1/3 topdress 5-7. days after panicle initiation [DAP]). This improves the plant's drought resistance by encouraging faster root growth and, thus, more soil area can be exploited for soil moisture.
· Increase soil organic maker (OM) content. OM improves the soil's water absorption and retention capacity.
· Minimum tillage (one plowing and one harrowing) reduces the water requirement for land preparation and speeds crop establishment, lowering the risks of an end-of-season drought. Minimum tillage is possible in fields where perennial weeds are few.
· Direct seedling of pregerminated seed can be used where there is not enough water to thoroughly prepare the land for transplanting. Direct seeding also results in a stronger root system. This gives the crop batter capacity to survive during short drought.
· Farmers should use the early rains of May for land preparation since this water largely goes to waste.
5. Altering the physical farm environment
· If feasible, impound water in one-fifth of the land area. A 200 sq.m structure will be enough to supply the water for a half hectare of rice crop and could also be used for fish production.
· Reduce the area planted to rice to increase the amount of irrigation or residual rainfall water available. The Sorjan system developed by farmers in Indonesia is one such method of water management. Tests done in Indonesia show that this system nearly doubled the amount of available water for rice production. Devote low-lying areas of the farm to rice and plant the upper areas with dryland crops. The rice crop can take advantage of the higher water table in the lower areas and can utilize runoff from the upper areas. (See the technology sheet on Sorjan: Towards Rice-based Integrated Cropping System.)
· Plant windbreaks to reduce evapotranspiration of the rice crop.
· At the national level, deforestation is the main cause of irrigated water shortages for rice production. For long-term sustainability, the nation's mountainous area must be reforested.