Assessment of Crop Water Productivity and Efficiency of Paddy Systems: A Comparison between Alternate Wetting and Drying and Conventional Flooding Methods

Water scarcity is still among the major challenges facing rice production as the gap between available water supply and water demand is increasing in many parts of the world, limiting future expansion of irrigation. Crop water productivity for rice was evaluated using the alternate wetting and drying (AWD) and continuous flooding irrigation (CF) methods to come up with the best method with higher productivity (WP) and water use efficiency (WUE). An experiment was carried out at Hembeti irrigation scheme, Morogoro region in Tanzania to investigate WP and WUE of paddy systems comparing the AWD and CF methods. The experiment was done in 2 seasons starting from July to September 2023 and from September to November 2023 using a rice variety locally known as SARO MALOLO (cross of YY and Super) with 90 day-growing duration from nursery to harvest. Two treatments namely, AWD and CF were arranged in a randomized complete block design with 3 replications to form 6 experimental plots each with 1m2 area separated by a 1 m buffer zone to prevent lateral movement of water. Plant spacing used was 20cm x 20cm forming 25 plants per square meter (1 seedling per hill). Several growth variables were monitored and data collected on daily and weekly basis. The growth parameters monitored were plant height, canopy cover, number of tillers and productive tillers, number of panicles and grain number. Findings show that WP was 4.05kgm-3 for AWD plots and 1.21kgm-3 for CF. It also shows that AWD achieved 75% of WUE compared to 41% in CF. Furthermore, AWD gave higher dry yield of 1.52 t ha⁻¹ than 1.33 t ha⁻¹ of dry yield in CF. This indicates that AWD performed much better compared to CF in terms of water use and yield. The results also showed that there was no significance difference in the number of productive tillers and panicles for both treatments at p=0.05, but with slight variation (significance difference) between the seasons and between the replicates. Results also showed significance difference in the amount of water applied and consumed for both treatments at p=0.05, where AWD managed to save 65.8% of irrigation water meaning AWD is the best method for regions with water scarcity as it can maintain or improve yield but with an advantage of less water input.