Assessing the impact of alternate wetting and drying irrigation on soil salinity, water productivity, and Boro rice yield in coastal saline regions of Bangladesh

Alternate Wetting and Drying (AWD) irrigation is widely promoted for rice cultivation to reduce water use and enhance water productivity. However, its performance under saline conditions remains insufficiently understood. Field experiments were conducted during the 2021-22 and 2022-23 seasons in the low-salinity (Barishal) and medium-salinity (Khulna) regions of coastal Bangladesh. Three irrigation treatments, including continuous flooding (CF), saturation, and AWD, were evaluated for rice cultivation across five locations in each region to assess soil salinity dynamics, rice yield, and water productivity. The salt-tolerant rice variety BRRI dhan67 was used in both regions. In Barishal, irrigation treatment did not significantly affect rice yield. However, AWD significantly improved irrigation water productivity compared with CF, by approximately 30% and 21% in 2021-22 and 2022-23, respectively (0.75 and 0.69 kg m − 3 under AWD, and 0.58 and 0.57 kg m − 3 under CF). Soil EC 1:5 increased with crop growth stage, but treatment differences were relatively small in the low-salinity environment. In contrast, in Khulna, soil EC 1:5 increased progressively during crop growth, with higher salinity observed under AWD and saturation than under CF. Average grain yield was about 14% lower under AWD than CF, while irrigation water productivity remained higher (21–29%) than CF. These findings indicate that AWD can improve irrigation water productivity without reducing yield in a low-salinity environment such as Barishal. However, in medium-salinity regions like Khulna, AWD was associated with greater soil salinity and lower grain yield, indicating that careful irrigation and salinity management are required. Further validation across a wider range of locations, seasons, and rice varieties is needed to identify conditions under which AWD can be safely implemented in coastal saline environments.