Water management in irrigated rice - Rice Knowledge Bank ...

Practical implementationSpecific information on minimum tillage andconservation agriculture technologies for rice can beobtained from the Rice-Wheat Consortium (www.rwc.cgiar.org/index.asp).3.5 What option where?The relative “attractiveness” of the above technologiesfor farmers to respond to water scarcitydepends on the type and level of water scarcity(Chapter 1.7), on the irrigation infrastructure (orthe level of control that a farmer has over the irrigationwater), and on the socioeconomics of theirproduction environment.With absolute, or physical, water scarcity,farmers have little choice but to adapt to receivingless water than they would need to keep their fieldscontinuously flooded. Figure 3.6 presents a gradientin relative water availability and some appropriateresponse options. On the far right-hand side of the(horizontal) water axis, water is amply availableand farmers can practice continuous flooding oflowland rice and obtain the highest yields. On thefar left-hand side, water is extremely short, suchas in rainfed uplands, and yields are very low. Goingfrom right to left along the water-availabilityaxis, water gets increasingly scarce and yields willdecline.Even with sufficient water available, goodland leveling, bund maintenance, construction offield channels, and thorough puddling (in the caseof puddled systems) will contribute to good cropgrowth and high yields. “Getting the basics right”is something that all farmers can do, no matterwhether they operate in large- or small-scale irrigationsystems or whether they use their own sourcesof irrigation (such as tubewells) or shared sources.After crop establishment, continuous ponding ofwater generally provides the best growth environmentfor rice and will result in the highest yields.After transplanting, water levels should be around 3cm initially, and gradually increase to 5−10 cm withincreasing plant height. With direct wet seeding, thesoil should be kept just at saturation from sowing tosome 10 days after emergence, and then the depthof ponded water should gradually increase withincreasing plant height. With direct dry seeding,the soil should be moist but not saturated from sowingtill emergence, or else the seeds may rot in thesoil. After sowing, apply a flush irrigation if thereis no rainfall to wet the soil. Saturate the soil whenplants have developed three leaves, and graduallyincrease the depth of ponded water with increasingplant height. In special problem soils, introducingsome form of alternate wetting and drying (AWD)105Yield (t ha –1 )Traditionalupland ricesystemFurrow, flush,sprinkler irrigationTechnologies to reduce water inputAerobic ricesystemAWD SSCSoil management,reduced water depthLowland ricesystem∆Y = f (variety, management)0LowAerobicWater availabilityFCSoil conditionSFloodedHighFig. 3.6. Schematic presentation of yield responses to water availability and soil condition in different rice production systemsand their respective technologies to reduce water inputs. AWD = alternate wetting and drying, SSC = saturated soil culture,FC = field capacity, S = saturation point, ΔY = change in yield. Adapted from Tuong et al (2005).29