Two field experiments were conducted to investigate rice-weed competition during direct-seeded rice cultivation. A rectangular hyperbolic equation was used to predict rice yield as a function of weed densities. Economic thresholds (ET) of multi-species weeds were estimated considering the cost of weed control and price of rice yield. The dry matter production and intraspecific competition of weeds were 1.13–3.63 g plant⁻¹ and 0.0375–0.0383, respectively. The competition effect of weeds on rice was significant and the competitivity value ranged from 0.0170 to 0.0126. Therefore, the number of panicles m⁻², grains panicle⁻¹ and 1,000-grain weight were significantly reduced by the competition of weed species. Considering the weed competitivity, weed control costs and price of grain, the ET values of weeds were 4.72–9.17 plants m⁻². These findings will be useful for weed management in direct-seeded rice cultivation.

Rice production in coastal tidal floodplains is severely constrained by periodic tidal submergence, making modern semi-dwarf varieties unsuitable. While local landrace cultivars are widely grown for their adaptability, their adaptation mechanisms and response to nitrogen management under tidal ecosystems remain poorly understood. This two-year on-farm study (aman seasons, 2021 and 2022) evaluated landrace rice cultivars against a modern check (BR23) under different nitrogen-management practices: urea super-granule deep placement and prilled urea application. Landraces adapted better to tidal submergence than BR23, exhibiting greater plant height, culm strength, biomass, and nutrient accumulation. Cultivar effects explained most of the variation in grain yield (38–40%), followed by nitrogen management (18–21%). Deep placement of urea super-granule significantly enhanced growth, yield, and nutrient uptake compared to prilled urea. Shorna showed the highest grain nitrogen uptake (48.23 kg ha⁻¹), agronomic efficiency (20.81 kg grain kg⁻¹ nitrogen), and partial factor productivity (71.91 kg grain kg⁻¹ nitrogen). Bhushiara achieved the highest grain harvest index (0.54) and nutrient harvest indices, indicating efficient nutrient partitioning to grains. During grain-filling, nitrogen and phosphorus efficiently remobilized to the grains, while potassium remained mostly in the straw. Ultimately, pairing resilient landraces like Shorna, Bhushiara, Dudmona, and Lalmota with optimized nitrogen management, specifically urea super-granule application, substantially improves productivity, nutrient efficiency, and climate resilience. This study provides some of the first comprehensive evidence on how genotype-specific adaptation and deep-placed nitrogen interact to support sustainable rice production in Bangladesh’s coastal floodplains.

Drought stress severely limits soybean productivity by impairing growth, physiological processes, and yield. This study evaluated the morpho-physiological, biochemical, and yield responses of three soybean genotypes (AGS 383, NCS 1, and BU Soybean-1) under control, moderate, severe, and extreme drought conditions to identify drought-tolerant genotypes. Drought significantly reduced plant growth, nodulation, dry matter, leaf area index, photosynthetic traits, chlorophyll content, and grain yield, with greater reductions under increasing drought severity. Among the genotypes, AGS 383 consistently performed best, producing taller plants, greater nodulation, higher biomass, larger leaf area index, higher photosynthetic rate (37.74 µmol m⁻² s⁻¹ under control), greater chlorophyll content, and the highest grain yield (2.21–1.30 t ha⁻¹ from control to extreme drought). NCS 1 maintained relatively stable leaf water status, stomatal conductance, transpiration, and accumulated the highest proline under severe drought, indicating effective osmotic adjustment. BU Soybean-1 retained comparatively higher leaf number and relative water content but showed lower biomass, photosynthetic capacity, and grain yield. Grain yield was positively associated with photosynthetic rate, chlorophyll content, plant height, water uptake, seed number, and 100-seed weight. Overall, AGS 383 showed the greatest drought tolerance and yield stability, making it a promising genotype for drought-prone environments and soybean breeding.

Under stressful rice ecosystems, crop yield can be sustained by the use of tolerant genetic material and/or improved agronomic practices. An experiment was carried out during Aman season to assess the plant survival and productivity of rice under nitrogen (N) management during pre- and post-submergence periods. BRRI dhan52, AZ7006, and BU dhan1 were grown under 14 days of submergence (14 DS) and control conditions. Two N management strategies were used: (i) urea super granule (USG at 7 days after transplanting, DAT) and (ii) prilled urea (PU, 1/3rd at 7 DAT + 1/3rd at 7 days after de-submergence (DADS) + 1/3rd at maximal tillering stage). Plant survival, lodging, chlorophyll content in the leaves and yield component of rice were negatively impacted by submersion. Submergence for 14 days reduced dry biomass by 86.73 to 93.72% and grain yield by 18.85 to 55.12% in rice as compared to no submergence. However, the application of USG improved plant survival (91%), increased panicle bearing tillers (21 hill -1 ), improved grain fertility (73%) and decreased spikelet sterility (27%) of AZ7006 as to PU treatment. By using USG in AZ7006, a minimum loss of grain and straw yield was achieved under 14 DS. The results of this study indicate that rice yield can be increased by 25.96% through applying USG under submergence condition. Therefore, the application of USG in the root zone offers a chance to increase the rice productivity of submergence tolerant varieties under flash-flood circumstances. Ann. Bangladesh Agric. 29(2): 67-91