Core Ideas Soil water release curve is important but difficult to measure. HYPROP and WP4 are used to develop the soil water release curves for three soils. HYPROP and WP4 provided a good and simple way to measure soil water release curves. A soil water release curve (SWRC) describes the critical and soil‐specific relationship between soil water content and matric potential. In this study, soil moisture and corresponding matric potentials were measured using (1) a new method by HYPROP and WP4 dewpoint potentiometer, and, (2) the traditional method by hanging water column, Tempe cell, and pressure plate. The SWRCs were developed for Fargo silty clay, Glyndon silty loam, and Hecla sandy loam soils by using the van Genuchten model. The goodness of fit between the fitted SWRC and the measured data agreed well with R2 between 0.91 and 0.98. The comparison for the fitted SWRCs showed that the SWRCs for Hecla sandy loam soil provided the best agreement while Glyndon silty loam soil had the best match in terms of slope and shape. The SWRCs for Fargo silty clay soil did not provide a good match between the two methods. The difference in water content between the two fitted SWRCs was less than 2% for Glyndon silty loam and Hecla sandy loam soils. However, Fargo silty clay had a 4.5 to 5% difference for 66% of the measurements, possibly due to the different bulk densities caused by shrinkage and swelling nature of the clay soil. Since the best fitted van Genuchten parameters were within the reference range that was acceptable for the same type of soils, the HYPROP and WP4 can be used to develop SWRCs that are comparable to the traditional laboratory methods for the three soils in the Red River Valley.

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.

An experiment was conducted at farmers' field aimed to evaluate the water saving technologies in Boro rice. The experiment involved three plots at 33 m, 65 m and 100 m distance from the water source. Each plot was divided into two parts to accommodate two management practices as research management (RM) and farmer's management (FM). RM comprised of plastic pipe water distribution system to reduce conveyance loss and alternate wetting and drying (AWD) method for field water management. FM comprised of earthen canal water distribution system and conventional irrigation method. BRRI dhan28 was cultivated with recommended agronomic practices. In RM, irrigation was applied when water level went 15 cm down below the ground surface where FM included conventional practice. Result showed that conveyance loss of water in earthen canal increased with increasing the distance from water source to field. Conveyance loss found 6.1 and 0.5 l s -1 per 100 m in earthen canal and plastic pipe distribution system, respectively. Plastic pipe distribution system successfully minimized 91.6% water loss that occurred in earthen canal. AWD practice alone saved 20.2% field water over conventional practice. Combination of AWD and plastic pipe had saved 42% water, Tk 2,270 ha -1 as electricity cost and Tk 2,947 ha -1 as irrigation cost over farmer's management. RM had higher yield than FM due to better performance of yield contributing parameters. Water productivity increased from 0.35 kg m -3 in FM to 0.65 kg m -3 in RM. Both the technologies in RM are environment friendly for reducing groundwater use in the irrigated ecosystem.

Ber (Zizyphus mauritiana Lamk.) is an indigenous delicious, nourishing fruit grown widely throughout the India but faces heavy fruit drop due to several biotic and abiotic stress factors resulted in declining trend of ber production over the year. Keeping these facts in foreground, replicated field experiment was conducted during 2013-14 and 2014-15 at HRS, Mondouri, BCKV, West Bengal with eleven treatments consist two different levels of NAA, GA 3 , 2,4-D, ZnSO 4 and H 3 BO 3 along with a control (water spray). Results of investigation revealed that application of 2,4-D @ 10 mg/l recorded highest fruit set (48.80%). Maximum fruit retention (42.83%) and total no. of fruits/tree (514) were obtained with the application of NAA @ 20 mg/l. Application of GA 3 @ 20 mg/l recorded significantly (p≤0.05) higher yield (30.67 kg/tree), fruit weight (60.5 g), fruit length (5.8 cm), fruit breadth (5.1 cm), pulp to seed ratio (13.9) and specific gravity (1.104) as well as economic returns over control during both the year of experiment. Among the treatments H 3 BO 3 at 0.4% recorded the highest TSS (11.7°Brix), total sugar (8.33%), reducing sugar (5.21%) and TSS: Acid (107.36) ratio with lowest fruit acidity (0.10 %) whereas highest vitamin-C content of fruit was recorded with GA 3 at 20 mg/l (64.68 mg / 100 g) followed by NAA at 20 mg/l. Results suggest that twice spraying of GA 3 @ 20 mg/l and H 3 BO 3 at 0.4% is vital for optimizing yield components, yield and quality of ber (cv. BAU Kul-1) in trans-Gangetic plains of West Bengal.

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Predicting surface runoff and flooding in seasonally frozen areas such as the Red River of the North Basin (RRB) in USA is a challenging task. It depends on the knowledge of the complex process of infiltration in frozen soil, such as phase changes of water, ice content and distribution in the infiltration zone (the top 0–30 cm of the soil profile), soil pore size distribution, soil temperature and freeze–thaw cycles. In this study, the infiltration rates into frozen soil (Colvin silty clay loam according to the United States Department of Agriculture (USDA) Classification, and Chernozem according to Food and Agriculture Organization of the United Nations (FAO) international soil Classification) were measured at three different initial water contents: permanent wilting point (PWP), θpwp; field capacity (FC), θfc; and between FC and PWP, θmid. Laboratory infiltration experiments were conducted using a Cornell sprinkle infiltrometer with three replications for each initial water content. Volumetric soil water content (θv) and soil temperature at three depths were also continuously monitored using sensors. The average infiltration rates were 0.66, 0.38, and 0.59 cm/min for three initial water contents (θpwp, θmid, and θfc, respectively). Initial infiltration into frozen soil occurred quickly in the soil with θpwp because the soil was dry. Melted ice water contributed to the total soil water content over time, so it made the initial infiltration comparatively slower in the soil with θmid. Initial infiltration was also slower in the soil with θfc because the wet soil had very small pore space, so the soil rapidly reached its saturation after the infiltration started. The Horton infiltration equation was fitted with the observed infiltration rates for the soils with three initial water contents, and the goodness of fit was evaluated by using the coefficient of determination (R2) and the root-mean-square error (RMSE). The final infiltration rates from the fitted Horton equations were 0.060, 0.010, and 0.027 cm/min for the initial water contents (θpwp, θmid, and θfc, respectively). The soil water content along the soil profile changed with the amount of infiltrating water over time. However, the initial soil water content and melt water from ice resulting from soil temperature rise regulated the change in soil water content. The amount of ice melt water contribution to soil water content change varied among the soils with different initial water contents (θpwp, θmid, and θfc, respectively). The θv changed gradually in the θpwp soil, rapidly at 0 °C in the θmid soil, and less in the θfc soil. The change in pore distribution due to freeze–thaw cycles and soil packing altered the soil hydraulic properties and the infiltration into the soil. This study can provide critical information for flood forecasting model and subsurface drainage design in the RRB.

Land surface temperature (LST) is a basic determinant of the global thermal behavior of the Earth surface. LST is a vital consideration for the appraisal of gradual thermal change for urban areas to examine the strength of the thermal intensity of the surface of urban heat island (SUHI) and to see how hot the surface of the Earth would be in a particular location. In this respect, the most developed urban city like Dhaka Metropolitan Area (DMA), Bangladesh is considered for estimation of LST, and Normalized Difference Vegetation Index (NDVI) changes trend in more developed and growing developing areas. The focus of this study is to find out the critical hotspot zones for further instantaneous analysis between these two types of areas. The trends of long-term spatial and temporal LST and NDVI are estimated applying Landsat images-Landsat 5-TM and Landsat OLI_TIRS-8 for the period of 1988 to 2018 for DMA and for developed and growing developing areas during the summer season like for the month of March. The supervised classification was used to estimate the land cover categories and to generate the LST trends maps of the different percentiles of LSTs over time using the emissivity and effective at sensor brightness temperature. The study found the change in land cover patterns by different LST groups based on 50th, 75th, and 90th percentile where the maximum LST for the whole DMA went up by 2.48˚C, 1.01˚C, and 3.76˚C for the months of March, April, and May, respectively for the period of 1988 to 2018. The highest difference in LST was found for the most recently developed area. The moderate change of LST increased in the built-up areas where LST was found more sensitive to climate change than the growing developed areas. The vegetation coverage area decreased by 6.

HighlightsHydraulic conductivity was measured in frozen and unfrozen soil conditions by a minidisk infiltrometer.In the RRB, frozen sandy loam and silty clay soils had the highest and lowest hydraulic conductivity, respectively.Three simple equations were developed for the three soils to predict frozen soil hydraulic conductivity.Freeze-thaw cycles reduced soil hydraulic conductivity.Abstract. Hydraulic conductivity (k) is a key parameter in describing water movement through a soil profile. In the Red River of the North basin (RRB), the hydraulic properties of frozen soils vary with temperature, water content, and other factors. In this study, a minidisk infiltrometer was used to measure the k values of three soils from the RRB: Colvin silty clay loam, Fargo silty clay, and Hecla sandy loam. The k values were measured for frozen and unfrozen soils with five different initial soil water contents: oven dry, permanent wilting point, field capacity, midway between permanent wilting point and field capacity, and saturation. The results showed that the mean k value of a frozen soil increased with an increase in initial soil water contents. Hecla soil had the highest k values and Fargo soil had the lowest k values for frozen soils. Three equations were fitted with the measured k values of Colvin silty clay loam, Fargo silty clay, and Hecla sandy loam soils. The k values were also estimated using the Motovilov model. When evaluating model performance, the fitted regression models agreed more closely with the measured k values (index of agreement, d, values of 0.96, 0.94, and 0.94 for Colvin, Fargo, and Hecla soils, respectively) than Motovilov models. Based on overall considerations of statistical measures, the fitted regression models predicted the k values better than Motovilov models for all three frozen soils. It was also found that the k values decreased with an increase in the number of the freeze and thaw cycles that changed the soil properties. Keywords: Frozen soil, Hydraulic conductivity, Mini disk infiltrometer, Red River Valley.