Impact of rainwater management on growth and yield of rainfed lowland rice

Continuous flooding of rice from emergence to maturity is believed to suppress rice growth and productivity. A field experiment was conducted in Fogera plain, northwestern Ethiopia, during the rainy season (June-October) in 2010 and 2011 to determine appropriate water management practices for rainfed lowland rice production. Ten water management treatments were studied in RCB design with three replications. The water management treatments included continuous flooding, draining water after every 15 days and re-flooding after one day, draining water after every 15 days and re-flooding after two days , draining water after every 15 days and re-flooding after three days , draining water after every month and re-flooding after one day , draining water after every month and re-flooding after two days , draining water after every month and re-flooding after three days , draining water after every one and a half month and re-flooding after one day , draining water after every one and a half month and reflooding after two days and draining water after every one and a half month and re-flooding after three days . Data on leaf area at heading, plant height, thousand seeds weight, and grain and aboveground biomass yields were collected and analyzed. Leaf area index (LAI), Crop Growth Rate (CGR), Net Assimilation Rate (NAR) and harvest index (HI) were computed. Results of the experiment indicated that with continuous flooding, LAI, CGR, NAR, plant height, number of productive tillers, number of filled spiklets, grain yield and biomass yield were highly depressed but improved when drainage and aeration were practiced. Compared to continuous flooding, a grain yield increment of 26 % was obtained due to draining and re-flooding the water from 15-days to one month interval. It is concluded that the productivity of rain-fed lowland rice was depressed in response to continuous flooding whilst it was enhanced in response to draining and re-flooding the water at least every month.