In Bangladesh’s hill regions, where there is less cultivable land, increasing crop output requires efficient land use. Thus, in this challenging farming setting, two crop-based patterns evolved into three or four crop-based patterns. To increase cropping intensity and farmer income by incorporating mustard and mungbean in a rice-based cropping pattern, a field experiment was carried out at Sadar and Panchari Upazila, Khagrachhari during 2017–2018 and 2018–2019. Two years’ mean data (using a block farming approach) showed that the modified pattern had produced a much higher yield through improved management practices. In the improved cropping pattern (Transplant aman (T. aman)–mustard–mungbean–aus rice), a higher rice equivalent yield (16.25 t ha⁻¹) was found due to the inclusion of mustard and mungbean in the existing rice-based cropping patterns T. aman–fallow–boro (9.87 t ha⁻¹) and T. aman–fallow–tomato (9.09 t ha⁻¹). The gross margin from the improved cropping pattern was 448,715 BDT, which was 44.26% higher than the mean gross margin (311,050 BDT) of the two existing cropping patterns. Farmers are interested in growing mustard and mungbean since both can easily cultivated in hilly areas and can yield great economic returns quickly. For the large-scale production of oil and pulse, the T. aman–mustard–mungbean–aus rice cropping pattern might be introduced in the Khagrachhari district of Bangladesh.

This study evaluated twenty-four Aman rice (Oryza sativa L.) germplasm for morphological variability and genetic diversity at the Bangladesh Institute of Nuclear Agriculture. The focus was on ten quantitative and thirty-two qualitative traits using a randomized complete block design (RCBD). Significant differences were observed among all traits, with Dilbazal achieving the highest grain yield g plant⁻¹ and Baishfuli the lowest. The genotypic coefficient of variation (GCV) was lower than the phenotypic coefficient of variation (PCV) for all traits, indicating environmental influence. High PCV and GCV, along with significant heritability and genetic advance (GA), were noted for filled and unfilled grains panicle⁻¹ and 1000-grain weight. Grain yield correlated positively with plant height, total and effective tillers, filled grains, unfilled grains, and thousand seed weight. Path coefficient analysis revealed direct positive effects of days to effective tillers, panicle length, and filled grains on grain yield. Cluster analysis grouped the germplasm into five distinct clusters, while qualitative assessments showed significant variation among genotypes, aiding in crop improvement efforts. Best performed genotypes were Vabmati, Nolkoshdhan, Dilbazal in cluster II for higher production and in cluster III Voirol, lalmota dhan-2 for highly scented germplasm.

Rice production faces critical challenges from water scarcity and greenhouse gas emissions, particularly in irrigated systems supplying half the global population. While alternate wetting and drying (AWD) irrigation and biochar amendments show individual promise for sustainability, their synergistic potential remains inadequately characterized. This study investigates whether combining these practices simultaneously enhances productivity, conserves water, and mitigates methane emissions in water-limited rice systems. Field experiments across two agroecological zones in Bangladesh (Boro season 2023-24) evaluated ten treatments combining irrigation methods (conventional flooding versus AWD) with biochar doses (0-20 t/ha) and fertilizer inputs. The optimal treatment 10 t/ha biochar with 50% recommended fertilizer under AWD (T8) achieved 6.4 t/ha grain yield (statistically equivalent to conventional management with full fertilizer), while reducing methane emissions by 40% and irrigation water requirements by 64%. Mechanistically, this integration operates through complementary pathways: AWD creates periodic aeration that elevates soil redox potential, disrupting anaerobic methanogenesis, while biochar enhances oxygen diffusion through improved porosity and increases alternative electron acceptors, collectively suppressing methane-producing microorganisms. These synergies improved soil organic carbon, nutrient availability, and water retention, sustaining yields with reduced chemical inputs. Robust treatment effects across contrasting soil types and principal component analysis demonstrate broad applicability. These findings establish that moderate biochar amendment combined with AWD irrigation represents a scalable, climate-smart strategy for sustainable rice intensification, reconciling food security with environmental stewardship in water-stressed regions.