Mitigating Global Warming Potentials and Optimizing Rice Productivity through Synergistic Effects of Irrigation Practices and Soil Amendments in Drought Prone Areas of Bangladesh

Irrigation water availability has become a major crisis for rice cultivation in the North-West Barind Tract areas of Bangladesh. Therefore, field experiments were conducted at Mohadebpur, Naogaon and Nachole, Chapainawabganj districts to find out the suitable water savings irrigation technique for sustaining rice productivity and controlling global warming potentials with different combinations of vermicompost, phosphogypsum and chemical fertilizers. The maximum grain yield 6760 - 6800 kg∙ha−1 were recorded in Vermicompost (10 t∙ha−1) with Phospho-gypsum (2.5 t∙ha−1) amendments along with reduced amount of Nitrogen fertilizer (N 25% of the recommended doze), followed by 6680-6700 kg ha−1 (Vermicompost 7.5 t∙ha−1 + phospho-gypsum 2.0 t∙ha−1 + N 50% RFD) under AWD irrigation. Aerobic irrigation saved 37.0% - 39.0% irrigation water, followed by 24.5% - 26.0% in alternate wetting and drying irrigation compared to the total required water (30,807 m3 ha−1) in conventional irrigation. The average cost for irrigation was calculated at 14,825 - 15,100 Tk∙ha−1 under conventional irrigation, which decreased to 11,775 - 11,850 Tk∙ha−1 for alternate wetting and drying, 9750 - 9825 Tk∙ha−1 for aerobic irrigation, respectively. The seasonal cumulative CH4 emission and GWPs for boro season rice cultivation significantly decreased with AWD and aerobic irrigation practices. The maximum seasonal cumulative CH4 emission, 221 kg/ha and 195 - 217 kg/ha, was recorded in Vermicompost (2.5 t/ha) with Phospho-gypsum (1.0 t∙ha−1) amendments under conventional irrigation, which were decreased by 21% - 23.0% and 24% - 25.0% for AWD and aerobic irrigation practices, respectively. The maximum GWPs value is 4875 - 5425 kg CO2-eq∙ha−1 was estimated for conventional irrigation with vermicompost (2.5 t∙ha−1) plus Phospho-gypsum (1.0 t∙ha−1) amendments, which was decreased by 19% - 21% for AWD and 22% - 23% for aerobic irrigations, respectively. Soil physico-chemical properties were also improved with 7.5 - 10 t∙ha−1 vermicompost and 2.0-2.5 t∙ha−1 Phospho-gypsum amendments. Conclusively, the integration of environment friendly irrigation water management through alternate wetting and drying (AWD), and aerobic irrigation with Vermicompost amendments (7.5 - 10 t∙ha−1) and half of the recommended Nitrogenous fertilizer application may enhance the synergistic effect towards optimum rice productivity, increased water productivity, improved irrigation cost savings and ensure mitigation of GWPs during dry season irrigated rice cultivation.