WATER MANAGEMENT STRATEGY FOR INCREASING MONSOON RICE PRODUCTION IN BANGLADESH

Different studies on water management for monsoon (transplanted aman) rice cultivation were conducted at BRRI farm, Gazipur from 1978-1988 to determine its economics and feasibility. It was observed that the necessity and benefit of supplemental irrigation mainly depend on the amount of rainfall and its distribution pattern during the season. The crop suffers from moisture stress when the rainfall ceases by the first week of October. Percent filled grains is seriously affected by moisture stress at the later part of crop growth but other growth parameters remain unaffected because of sufficient rainfall during the crop development stage. Under these circumstances, one timely supplemental irrigation of about 60 mm can increase the rice yield up to 59% relative to the rainfed condition. Besides that, benefit-cost ratios of 5.3 and 11.7 (for different devices) indicated that supplemental irrigation is highly profitable for monsoon rice production. A pond size of about 5% of the total cultivable land area is required to store enough water for one supplemental irrigation, and it is economically viable with a benefit-cost ratio of about 2.4. Moreover, where there is no source of supplemental irrigation, a well-managed 15 cm high level is very effective (91%) in rain water conservation and can reduce yield loss to about 21%.