Soybean (Glycine max) is a high water-demand crop and grown under moderate temperature in Japan. To protect the crop from hot summer and to utilize rainfall for its cultivation, selection of appropriate mulching material(s) is crucial. For optimum production of the crop, soil moisture and temperature regimes as well as water use efficiency (WUE) of the crop were investigated under straw, grass, paper, plastic and bare soil (control) mulching under rain-fed condition at Gifu university farm in Japan. The mulching treatments, compared to the control, lowered soil temperature by 2 °C at 5 cm depth and 0.5 °C at 15 and 25 cm depths. The plastic and straw mulching stored the highest quantity of soil moisture at 5 and 15 cm depths; the bare soil stored the lowest quantity. At 25 cm depth, soil-moisture content was the highest under paper mulch but invariable under the other mulches. Plastic mulching reduced evaporation rate from the soil surface and, consequently, the reduced soil-water consumption (SWC) from the root zone augmented WUE of soybean. The paper mulching, by conserving soil-moisture and reducing soil temperature, provided better crop growth attributes, while the plastic mulching improved WUE of green soybean. Therefore, the plastic mulch performed best in reducing soil-water consumption and increasing WUE, while the paper mulch was good for soil-moisture conservation and temperature modification that increased soybean yield. Keywords: Mulching, Soil-water consumption, Soil temperature, Water use efficienc

Historical trends of the annual maximum and minimum depths of groundwater tables (GWTs) that are indicative of sustainability status of groundwater resources still remain inadequately studied in the North-West (NW) hydrological region of Bangladesh. This study aimed at evaluating long-term (1985–2016) trends of GWTs of 350 monitoring wells and their impacts on groundwater development status in that region. The trends of the annual maximum and minimum depths of GWTs were determined and evaluated by using MAKESENS trend model. The functionality of suction-mode pumps was identified based on the annual maximum depth of GWTs. A significant (p ≤ 0.05) falling trend of the annual maximum depths of GWTs in 65.71% of the monitoring wells revealed continuous increase in groundwater abstraction. A significant falling trend of the annual minimum depths of GWTs in 69.71% of the monitoring wells revealed groundwater mining. GWTs remained below the suction limit (≈6 m) for 3 to 6 months in each year in 59.72% of the monitoring wells and for the whole year in 15.14% of the monitoring wells, making suction-mode pumps inoperable and creating domestic water scarcity. Therefore, groundwater extraction in many locations has become unsustainable, and hence, measures such as artificial recharge to the aquifers and water-saving technologies are needed to prevent groundwater mining.

The North-West (NW) region of Bangladesh is pivotal for the country’s agricultural development, mainly in producing irrigated Boro rice. However, increasing cost of irrigation water, fertilizers, labour and other inputs, and the spatio-temporal variation in actual yield, market price and profitability of rice, have added uncertainty to the sustainability of Boro rice cultivation. In this study, we evaluated the productivity, profitability, and prospect of Boro rice production using comprehensive field data collected directly from 420 farmers’ fields over two consecutive seasons (2015–16 and 2016–17), across seven geographically distributed locations in the NW region. We also analyzed the risk and return trade of popular Boro rice cultivars using Monte-Carlo simulation. The results show that there were significant (p≤0.05) variations in rice yield between sites, irrigation pump-types, and rice varieties, with Hybrid rice and BRRI dhan29 producing highest yields (6.0–7.5 t/ha). Due to different pricing systems, the cost of irrigation water varied from site to site and from year to year, but always comprised the highest input cost (20–25% of total production). The total paid-out cost, gross benefit, and gross income of rice significantly (p≤0.05) differed between sites, type of irrigation pumps, rice varieties, transplanting dates, and two cropping years. The variations in observed yield and profitability reveal considerable scope to improve rice production systems. Market variation in the price of rice affected overall profitability significantly. Probability and risk analysis results show that Minikit and BRRI dhan29 are the most stable varieties for yield and profitability. Hybrid rice, which has the maximum attainable yield among the cultivated rice varieties, also has the risk of negative net income. Based on the analysis, we discussed ways to improve yield and profitability and the prospect of Boro rice cultivation in the region. The study provides valuable information for policy-makers to sustain irrigated rice cultivation in both the NW region and nationally.