Effects of Integrated Nutrient Management and Urea Deep Placement on Rice Yield, Nitrogen Use Efficiency, Farm Profits and Greenhouse Gas Emissions in Saline Soils of Bangladesh

Abstract
Soil salinity is one of the major yield-limiting factors in the coastal ecosystems of Bangladesh. An efficient fertilizer management practice and selection of appropriate crop cultivars could play a crucial role in improving yield and promoting low-carbon agriculture across saline soils. A two-year multi-location field experiment was conducted during the Boro (dry) season (December–April) to investigate the effects of fertilizer management and rice cultivar selection on rice yield, economic viability, and global warming potential (GWP) in coastal saline soils of Bangladesh. The study included seven fertilizer treatments with varying nitrogen rates and sources, as well as two rice cultivars (BRRI dhan67 and BRRI dhan88). The results showed that integrated nutrient management-2 (INM-2) significantly (p < 0.05) increased rice yield and nitrogen use efficiency compared to other treatments for both BRRI dhan67 and BRRI dhan88. Similarly, INM-2 gave a higher return on fertilizer investment and marginal benefit-cost ratio than other treatments in both locations and under both cultivars. BRRI dhan67 significantly (p < 0.05) increased rice yield relative to BRRI dhan88 by 21 % and 52 % at the BRRI farm and Kaliganj in Satkhira, respectively. The cost-dominant analysis excluded BRRI dhan88 and all fertilizer treatments, except urea deep placement (UDP) and INM-2, from consideration in both locations. Consequently, INM-2 and UDP proved to be economically viable in both locations, with INM showing a higher marginal rate of return than UDP in BRRI dhan67. In terms of environmental sustainability, UDP significantly (p < 0.05) reduced GWP and yield-scaled emissions of CH4 by 31 % and 38 % without causing yield loss compared to INM-2. Similarly, BRRI dhan67 significantly (p < 0.05) reduced GWP and yield-scaled emissions of CH4 by 5 and 22 % compared to BRRI dhan88. These findings suggest that selecting salt-tolerant rice cultivars and implementing appropriate fertilizer management practices can enhance economic profitability, ensure food security, and mitigate the adverse effects of climate change in coastal saline soils.
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