Investigating water productivity and yield of boro rice under conventional and conservation irrigation practices in Bangladesh

Abstract

Irrigation is one of the vital inputs to rice production in Bangladesh, where 78% of irrigation is dependent on groundwater (GW) resources. For the past two decades, GW level has been significantly declining across the country and on the other hand, surface water is limited in the dry season. This poses a great challenge to meet burgeoning irrigation demand of the country. Amid this situation, optimal and judicial use of water for irrigation is being thought to be a way out without compromising crop yield. In such context, an experiment was performed at the Field Irrigation Laboratory, Bangladesh Agricultural University in Mymensing to investigate the water productivity, growth and yield characteristics of BRRI dhan28 under three different irrigation techniques i.e. alternate wetting and drying (AWD), raised bed (RB), and conventional continuous flooding (CF). Six treatments including four AWD variants with three replications for each treatment were laid out randomly in 18 plots. The highest yield was 6.63±0.65 t ha⁻¹ under 10 cm disappearance AWD treatment (T₂). But the lowest yield was (5.73±1.25 t ha⁻¹) under mixed AWD treatment (T₅) which did not show a significant variation on the yield of different techniques. CF treatment (T₁) needed 68.94±3.44 cm of water and its water productivity was 0.48±0.08 kg m⁻³, where the T₂ treatment needed average 52.10±3.21 cm of water and average water productivity was 0.59±0.04 kg m⁻³. The study revealed that 10 cm, 15 cm, 20 cm disappearance AWD and mixed AWD treatments (respectively, T₂, T₃, T₄, and T₅) saved 24.42, 24.28, 28.92 and 38.56% of irrigation water, respectively, and where the RB also saved 15.52% over the conventional method. On the basis of the above consideration, it can be concluded that AWD technology can be adopted to increase the water productivity of dry season boro rice and thus to make its cultivation more profitable.