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This paper proposes a heat-wave definition for Bangladesh that could be used to trigger preparedness measures in a heat early warning system (HEWS) and explores the climate mechanisms associated with heat waves. A HEWS requires a definition of heat waves that is both related to human health outcomes and forecastable. No such definition has been developed for Bangladesh. Using a generalized additive regression model, a heat-wave definition is proposed that requires elevated minimum and maximum daily temperatures over the 95th percentile for 3 consecutive days, confirming the importance of nighttime conditions for health impacts. By this definition, death rates increase by about 20% during heat waves; this result can be used as an argument for public-health interventions to prevent heat-related deaths. Furthermore, predictability of these heat waves exists from weather to seasonal time scales, offering opportunities for a range of preparedness measures. Heat waves are associated with an absence of normal premonsoonal rainfall brought about by anomalously strong low-level westerly winds and weak southerlies, detectable up to approximately 10 days in advance. This circulation pattern occurs over a background of drier-than-normal conditions, with below-average soil moisture and precipitation throughout the heat-wave season from April to June. Low soil moisture increases the odds of heat-wave occurrence for 10-30 days, indicating that subseasonal forecasts of heat-wave risk may be possible by monitoring soil-moisture conditions. [ABSTRACT FROM AUTHOR]

The present study is aimed at examining the rainfall changes and their relationship to vegetation dynamics in the central-coastal region of Bangladesh. Different statistical tests were used in the study to investigate the rainfall changes, such as the Mann-Kendall test and Sen's slope estimation. The normalized difference vegetation index (NDVI) time series were collected from Google Earth Engine and processed in R programming to examine the level and extent of vegetation coverage. A correlation analysis was used to determine the association between the total rainfall (June–September) and mean NDVI (October–November). Results depict that annual rainfall decreased in all the stations, with the highest values in Senbag (Z = -5.16 and Q = 55.24). The post-monsoon variability exhibited an increasing trend in the majority of the stations, whereas other seasons showed a decreasing trend with the highest values in Feni (pre-monsoon Z = -2.37 and monsoon Z = -2.49). The relationship between rainfall and vegetation dynamics (NDVI) was observed, which was a moderate to strong positive lag correlation throughout the region. It was also noticed that the locations with higher rainfall fluctuations have a weaker association with the NDVI. Reduced rainfall can reduce vegetation productivity by disrupting growth seasons, lowering soil water content, and increasing salinity in the area. It is expected that the findings will contribute to a better understanding of the impacts of climate change induced rainfall variability and the response of the vegetative environment to it. [ABSTRACT FROM AUTHOR]

Due to the combined effect of biotic and abiotic constraints, rising population pressure, and inelastic demand in the crop and horticulture sector, Bangladesh has had to adopt heavily subsidized and intensified fertilizer policies to enhance crop productivity, achieve and sustain self-sufficiency in food production, and food security provision. Although the initiative has played a vital role in boosting production, it has also invigorated the unbalanced amount of fertilizer application practices raising questions about maintaining biodiversity and ecosystem services while feeding the nation's population. Further research in this area must thus be applied to monitor and improve this sector. This study attempts to understand the issue by investigating the factors influencing Boro rice farmers' adoption decisions of recommended fertilizer doses. The study employs an ordered probit model with a sample selection approach. The investigation is based on collected data from 405 randomly selected farmers using a face-to-face interview method. The farmers were classified into low, middle, high and non-adopter groups. The study revealed that farmers' age, land typology, soil water retention, knowledge, and availability of cow dung significantly influenced farmers' decision to apply fertilizers. However, farmers' carry an aversion to following recommendations for fertilizer application due to their ambiguity about the whole system, their current fertilizer application-seeking behavior, and the lack of understanding of the environmental benefits of adoption. These issues urge policy interventions to initiate village-based demonstration programs that synthesize better synergies between recommended dose adoption, yield amelioration, sustainable soil care, and economics. [ABSTRACT FROM AUTHOR]

Optimum soil physical conditions for crop establishment are more likely to occur with mechanised row‐sowing using metered seeding and controlled depth placement of seeds than with broadcast sowing, that is common in many traditional South Asian cropping practices. Establishment success is a limitation for post‐rice crops in medium to heavy textured soils in the Eastern Gangetic Plain because sowing coincides with rapid topsoil drying and increases in soil strength. In addition, due to lack of rainfall in the post‐rice season the crop relies on access to stored soil water during vegetative and reproductive growth to achieve adequate yields. Our aim was to determine whether decreased soil disturbance (from full tillage to zero tillage (ZT) to undisturbed soil (Fallow)) and direct seeding (using small‐scale seeders) could 1) enhance chickpea crop establishment by conserving seedbed soil water and 2) alter crop water use of the water stored in the soil profile. The silt loam soil has an estimated volumetric soil water content (θv) of 34% at field capacity. At sowing, θv in the seedbed was between 25% to 29%. This was adequate for successful chickpea crop establishment, but slightly wetter than optimum for tillage. In the wet soil at sowing, there was evidence of smeared furrow walls and poor soil covering of the seed in the seedbed in strip planting (SP; rotating blades in front of tine) and ZT. Uncovered furrows (in ZT; using a tine opener) and the fallow soil lost more surface soil water (9%, 23 days after sowing) than the seedbeds created with greater levels of soil disturbance. In 2008, grain yield of single‐pass shallow tillage (SPST) was greater than SP but in 2009, grain yields of all one‐pass tillage techniques (ZT, SP, SPST) were greater than in the broadcast seeding in fully tilled soils. The improvement in chickpea yields was attributed to greater plant numbers, early plant vigour and root growth. Chickpea roots were found to 60 cm depth in the soil profile, and soil water content was less than the θv of wilting point to this depth at podding. There is evidence that root growth and plant water uptake occur deeper in these soil profiles to achieve the grain yields > 1,000 kg/ha recorded in this study. Mechanised sowing in rows with small‐scale seeders has the capability to overcome establishment and yield limitations for chickpea on medium to heavy soils in the post‐rice season. [ABSTRACT FROM AUTHOR]

The current study has been derived to understand morphometric parameters to pledge the reduction in the proclaimed drought influence for climate change. Watershed prioritization has been studied using the geographical information system and remote sensing techniques for soil erosion and water preservation measure at Plio–Pleistocene elevated tract in Bangladesh. Secondary data, i.e., SRTM DEM and the topographical sheets, have been used for the drainage network identification. Seventeen watersheds of fifth order and three watersheds of sixth order are selected for the whole study. Sixteen basic morphometric parameters that are categorized as areal, linear and relief aspects have been used for the study area. The study area comprises sixth stream order that has been obtained using a stream threshold value of 100-m length. Morphometric analysis is suitable for water and soil conservation practice where groundwater and relevant data sets are not available. For the categorization and correlation of the morphometric parameters, principal component analysis (PCA) has been used in the present study. PCA analysis is more suitable, well-known and widely used method for its simplicity to choose more influencing parameters (correlated parameters) that are responsible for watershed prioritization. Strongly correlated components (Dd, Rc, Re and Rb) are used for the compound parameter (Cp) and final priority (Rp) calculation. Low Cp value is suitable for water and soil conservation measure. Therefore, the corresponding low Cp has been taken as one for final priority ranking (Rp) purpose, then second lowest value as two, and so on. [ABSTRACT FROM AUTHOR]

Climate extremes such as droughts and intense rainfall events are expected to strongly influence global/regional water resources in addition to the growing demands for freshwater. This study examines the impacts of precipitation extremes and human water usage on total water storage (TWS) over the Ganges-Brahmaputra-Meghna (GBM) River Basin in South Asia. Monthly TWS changes derived from the Gravity Recovery And Climate Experiment (GRACE) (2002-2014) and soil moisture from three reanalyses (1979-2014) are used to estimate new extreme indices. These indices are applied in conjunction with standardized precipitation indices (SPI) to explore the impacts of precipitation extremes on TWS in the region. The results indicate that although long-term precipitation do not indicate any significant trends over the two subbasins (Ganges and Brahmaputra-Meghna), there is significant decline in rainfall (9.0 ± 4.0 mm/decade) over the Brahmaputra-Meghna River Basin from 1998 to 2014. Both river basins exhibit a rapid decline of TWS from 2002 to 2014 (Ganges: 12.2 ± 3.4 km3/yr and Brahmaputra-Meghna: 9.1 ± 2.7 km3/yr). While the Ganges River Basin has been regaining TWS (5.4 ± 2.2 km3/yr) from 2010 onward, the Brahmaputra-Meghna River Basin exhibits a further decline (13.0 ± 3.2 km3/yr) in TWS from 2011 onward. The impact of human water consumption on TWS appears to be considerably higher in Ganges compared to Brahmaputra-Meghna, where it is mainly concentrated over Bangladesh. The interannual water storage dynamics are found to be strongly associated with meteorological forcing data such as precipitation. In particular, extreme drought conditions, such as those of 2006 and 2009, had profound negative impacts on the TWS, where groundwater resources are already being unsustainably exploited. [ABSTRACT FROM AUTHOR]

Sowing of chickpea in the heavy-textured soils of north-west Bangladesh with minimum tillage technology aims to increase the timely planting of large areas during a relatively short sowing window before soil water deficit limits germination and emergence. However, the seedbed conditions into which chickpea is sown need to be better quantified, so that limiting factors which affect germination and emergence can be identified. Two of the soil physical characteristics of importance are soil water and aeration. Growth cabinet studies have identified the fastest germination and emergence of chickpea on representative soils for this area at gravimetric water contents of 17-18 %, whilst soil water contents above and below this delayed germination and emergence. Emergence was recorded at soil water potentials between field capacity (−10 kPa) and wilting point (−1500 kPa). Emergence was possible at lower soil water potentials in the finer textured soil, whilst in coarser textured soil, emergence was still possible at higher soil water potentials. [ABSTRACT FROM AUTHOR]

Rice-fallow and rice-rice are major cropping systems in the salt affected region of the Ganges Delta covering West Bengal, India and Bangladesh. The dry season rice (Boro) is grown mostly by irrigation from ground water in this water scarce region. Boro encounters soil and water salinity, air temperature fluctuations and intense evaporative demand. We studied six sowing dates (1 October, 15 October, 1 November, 15 November, 1 December and 15 December) and three varieties (WGL 20471, Bidhan 2 and IET 4786) of rice to find an interacting effect on yield and water productivity. Soil and water salinity varied during the growing period with lower soil salinity during the month of November (2.20–2.53 dS m−1) and higher soil salinity towards the end of the growing season (4.30–5.23 dS m−1). The mean field water salinity was higher (1.78 dS m−1) during the Boro 2017–18 compared to that (1.65 dS m−1) during 2016–17, as about 49 mm rainfall was received in the month of March 2017. Sowing dates significantly affected the yield of Boro rice. Earliest sowing on 1 October is not feasible as it significantly reduced the grain and straw yields. Sowing of nursery up to 1 of November was found to be the best possible option, and it should not be delayed up to 15 December. The rice variety IET 4786 was found to be susceptible to salinity with the lowest grain yield 2.65–2.98 t ha−1, compared to Bidhan 2 (3.41–5.95 t ha−1) and WGL 20471 (3.40–5.81 t ha−1). Both irrigation and economic water productivity of Boro were affected by sowing dates and variety. Rice variety IET 4786 required less irrigation water (1320 mm) than the other two varieties (1350 mm). Higher (>0.5 kg m−3) irrigation water productivity of Boro can be achieved by selecting salt tolerant varieties (WGL 20471 and Bidhan 2) and optimum sowing window of 1–15 November. [ABSTRACT FROM AUTHOR]

Drought is an intricate atmospheric phenomenon with the greatest impacts on food security and agriculture in South Asia. Timely and appropriate forecasting of drought is vital in reducing its negative impacts. This study intended to explore the performance of the evaporative stress index (ESI), vegetation health index (VHI), enhanced vegetation index (EVI), and standardized anomaly index (SAI) based on satellite remote sensing data from 2002–2019 for agricultural drought assessment in Afghanistan, Pakistan, India, and Bangladesh. The spatial maps were generated against each index, which indicated a severe agricultural drought during the year 2002, compared to the other years. The results showed that the southeast region of Pakistan, and the north, northwest, and southwest regions of India and Afghanistan were significantly affected by drought. However, Bangladesh faced substantial drought in the northeast and northwest regions during the drought year (2002). The longest drought period of seven months was observed in India followed by Pakistan and Afghanistan with six months, while, only three months were perceived in Bangladesh. The correlation between drought indices and climate variables such as soil moisture has remained a significant drought-initiating variable. Furthermore, this study confirmed that the evaporative stress index (ESI) is a good agricultural drought indicator, being quick and with greater sensitivity, and thus advantageous compared to the VHI, EVI, and SAI vegetation indices. [ABSTRACT FROM AUTHOR]

Puddling of clay soils for rice transplanting causes a loss of soil structure and vertical shrinkage cracks that are hypothesized to hamper sunflower root growth in the following dry season. To alleviate soil constraints for sunflower root growth and yield, we examined the effects of three levels of mulch and two irrigation regimes in the dry season on a clay-textured soil in the coastal zone of Bangladesh. These treatments were no-mulch, rice straw mulch at 5 t ha−1 and 10 t ha−1, irrigation applied to the field capacity (I1) and a water supply double that of the I1 treatment (I2). The rice straw mulch significantly increased soil water content by 3–9% and decreased soil penetration resistance by 28–77% and crack volume by 84–91% at A 0–30 cm soil depth relative to the no-mulch treatment. The better root development with the rice straw mulch increased sunflower yield by 23%. No benefit or further reduction in soil penetration resistance or yield improvement was obtained from increasing the level of mulch from 5 to 10 t ha−1 or the volume of irrigation water. It is concluded that ameliorating soil constraints by mulch application led to better root growth in the upper root zone and the increased yield in the clay soil. [ABSTRACT FROM AUTHOR]