The relative performance of global climate models (GCMs) of phases 5 and 6 of the Coupled Model Intercomparison Project (CMIP5 and CMIP6, respectively) was assessed in this study based on their ability to simulate annual and seasonal mean rainfall and temperature over Bangladesh for the period 1977-2005. The multiple statistical metrics were used to measure the performance of the GCMs at 30 meteorological observation stations. Two robust multicriteria decision analysis methods were used to integrate the results obtained using different metrics for an unbiased ranking of the GCMs. The results revealed MIROC5 as the most skilful among CMIP5 GCMs and ACCESS-CM2 among CMIP6 GCMs. Overall, a significant improvement in CMIP6 MME compared to CMIP5 MME was noticed in simulating rainfall over Bangladesh at annual and seasonal scales. CMIP6 MME also showed significant reduction in maximum and minimum temperature biases over Bangladesh. However, systematic wet and cold biases still exist in CMIP6 models for Bangladesh. CMIP6 GCMs showed higher spatial correlation with observed data compared to CMIP5 GCMs, but higher difference in terms of standard deviations and centered root mean square errors, indicating better performance in simulating geographical distribution but lower performance in simulating spatial variability of most of the climate variables for different timescales. In terms of Taylor skill score, the CMIP6 MME showed higher performance in simulating rainfall but lower performance in simulating temperature compared to CMIP5 MME for most of the timeframes. The findings of this study suggest that the added value of rainfall and temperature simulations in CMIP6 models is incompatible with the climate models used in this research.

Agricultural productivity is affected by air temperature and CO 2 concentration. The relationships among grain yields of dry season irrigated rice (Boro) varieties (BRRI dhan28, BRRI dhan29 and BRRI dhan58) with increased temperatures and CO 2 concentrations were investigated for futuristic crop management in six regions of Bangladesh using CERES-Rice model (DSSATv4.6). Maximum and minimum temperature increase rates considered were 0˚C, +1˚C, +2˚C, +3˚C and +4˚C and CO 2 concentrations were ambient (380), 421, 538, 670 and 936 ppm. At ambient temperature and CO 2 concentration, attainable grain yields varied from 6506 to 8076 kg·ha −1 depending on rice varieties. In general, grain yield reduction would be the highest (13% -23%) if temperature rises by 4˚C and growth duration reduction would be 23 -33 days. Grain yield reductions with 1˚C, 2˚C and 3˚C rise in temperature are likely to be compensated by increased CO 2 levels of 421, 538 and 670 ppm, respectively. In future, the highest reduction in grain yield and growth duration would be in cooler region and the least in warmer saline region of the country. Appropriate adaptive techniques like shifting in planting dates, water and nitrogen fertilizer management would be needed to overcome climate change impacts on rice production.

Unpuddled transplanting of rice is gaining attention in Bagnaldesh agriculture. Energy budget is essential for efficient management of the resources in agricultural production. The energy balance under different minimum tillage practices in rice cultivation was assessed during 2009-11 by comparing the parameters: energy input, energy output, energy productivity and energy output:input ratio. Energy input in CT, SPWT, BP and ST were 25.50, 23.15, 20.48 and 20.49 GJ ha -1 , respectively in rice cultivation. Maximum energy was consumed for chemical fertilizers. Tillage energy ranked second in conventional tillage and ranked fourth in minimum tillage options. Energy output was insignificant due to insignificant yield difference. Unpuddled transplanting (BP and ST) showed 8-12% increase in energy productivity and 22-24% increase in energy output:input ratio. However, from the energy saving point of view, unpuddled transplanting may be considered better options depending on the resources availability in rice cultivation.

In the changing climatic condition, temperature is the most vulnerable parameter and is projecting a trend of increase in the future. Crop growth and development process depend largely on air temperature. This study aims to determine the role of increasing air temperature in yield, crop water requirement (CWR), and other agronomic parameters of irrigated rice. Ceres-rice model associated in the Decision Support System for Agrotechnology Transfer (DSSAT) was used in 15 different locations of Bangladesh. Grain yield, growth duration, and crop water requirement of widely cultivated irrigated rice (Boro rice) variety BRRI dhan28 were analysed in normal temperature and elevated air temperature by 1°C, 2°C, 3°C, and 4°C. The result revealed detrimental effect of elevated temperature on growth duration and grain yield. The estimated highest growth duration reduction of 30 days was found in Moulvibazar for 4°C temperature rise. The grain yield reduction was projected by 0–17%, 16–35%, 31–49%, and 39–61% from the normal condition if the seasonal mean temperature increased by 1°C, 2°C, 3°C, and 4°C, respectively. The country average crop water requirement was found to be 405 mm of which the highest 445 mm and the lowest 358 mm were recorded in Moulvibazar and Chandpur, respectively. The study revealed that the country average rice CWR reduced by 5%, 8%, 12%, and 17% over the normal condition for 1°C, 2°C, 3°C, and 4°C rising temperature, respectively. For 1°C temperature rise, BRRI dhan28 life span shortened by 6.4 days, grain yield reduced by 695 kg, and estimated CWR decreased by 14 mm. The projected declining CWR indicated that irrigated rice will require less irrigation water, but it will cause considerable yield loss under elevated temperature. Though elevated temperature will save huge irrigation water used in country-wide Boro rice cultivation, the crop developers need to introduce new heat-tolerant cultivar to minimize yield loss.

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Decomposed organic materials, in combination with plant growth-promoting bacteria (PGPB), are environmentally friendly and reduce synthetic fertilizer use in rice production. A bio-organic fertilizer (BoF) was prepared using kitchen waste (79%), chita-dhan (unfilled rice grain) biochar (15%), rock phosphate (5%), and a consortium of 10 PGPB (1%) to supplement 30% nitrogen and to replace triple superphosphate (TSP) fertilizer in rice production with an improvement of soil health. PGPB were local isolates and identified using 16S ribosomal RNA partial gene sequences as Bacillus mycoides, Proteus sp., Bacillus cereus, Bacillus subtilis, Bacillus pumilus, Paenibacillus polymyxa, and Paenibacillus spp. Isolates could fix N2 by 0.7–1.4 g kg–1, solubilize 0.1–1.2 g kg–1 phosphate, and produce 0.1–40 g kg–1 indoleacetic acid. The performance of BoF was evaluated by 16 field experiments and 18 farmers’ field demonstration trials during the year 2017–2020 in different parts of Bangladesh. Performances of BoF were evaluated based on control (T1), full synthetic fertilizer dose of N, P, and K (T2), BoF (2 t ha–1) + 70% N as urea + 100% K as muriate of potash (T3), 70% N as urea + 100% P as TSP + 100% K as muriate of potash (T4), and 2 t ha–1 BoF (T5) treatments. At the research station, average grain yield improved by 10–13% in T3 compared with T2 treatment. Depending on seasons, higher agronomic N use efficiency (19–30%), physiological N use efficiency (8–18%), partial factor productivity (PFP)N (114–150%), recovery efficiency (RE)N (3–31%), N harvest index (HIN) (14–24%), agronomic P use efficiency (22–25%), partial factor productivity of P (9–12%), AREP (15–23%), and HIP (3–6%) were obtained in T3 compared with T2 treatment. Research results were reflected in farmers’ field, and significant (P < 0.05) higher plant height, tiller, panicle, grain yield, partial factor productivity of N and P were obtained in the same treatment. Application of BoF improved soil organic carbon by 6–13%, along with an increased number of PGPB as compared with full synthetic fertilizer dose. In conclusion, tested BoF can be considered as a green technology to reduce 30% synthetic N and 100% TSP requirements in rice production with improved soil health.

This study is focused on the possibility of using coal mine wastes as a replacement for conventional road subgrades. Various laboratory tests carried out on fresh coal mine waste collected from Barapukuria Coal Mine (Located at Dinajpur, Bangladesh) showed that, it behaves like low strength soil with 0.71% CBR and 18.74% plasticity index which is unsuitable for engineering utilization. Later, fine sand and cement were added with the waste. Three different cement proportion were tested (5%, 8% and 10% of total weight) keeping a constant sand proportion (20% of total weight). The unconfined compression strength and CBR value were found to increase greatly. Analyzing the test results, waste mixed with 8% cement and 20% sand showing 27.44% CBR and 9.09% plasticity index was found to be effective for using as subgrade. Chemical analysis of waste detected the presence of lead as 0.026 ppm which may cause groundwater contamination.

Exploring the homogeneity (or heterogeneity) at sub-national level is crucial as it associated with design, budget allocation and implementation of a research project. Since demographic and socioeconomic factors depict the first valuable insight of a community, it is imperative to explore the homogeneity within a country by considering these variables. Yet, the information on this aspect is scarce in Bangladesh. Therefore, the present study aimed to identify the district and district town specific homogeneity in Bangladesh. The data for this study were extracted from the most recent Housing and Population Census of the country, and the multivariate cluster analysis was employed to identify the natural groups or segments. We found that Bangladesh could be classified into three distinct clusters both at district and district town levels based on demographic and socioeconomic factors. The findings of this study would provide insights to the policymakers and researchers for designing and implementing community-based research initiatives, particularly in the area of public health and social science as well as market analysis research. The findings could also be helpful in the situation when the national representation of data is required with budget and time constraints.