查看更多>>摘要：? 2022 Elsevier B.V.Groundwater resources carrying capacity (GRCC) is defined as the capacity of groundwater resources for supporting social-economic development, which has been incredibly reduced in groundwater-depended agricultural regions due to unreasonable use of groundwater resources. Identifying the key factors influencing GRCC and providing the optimal strategy is critical for sustainable use of groundwater resources. The present study used the improved GRCC index, regression functions, and random forest to identify the key factors influencing the GRCC in a groundwater over-exploited area [Zhangjiakou, Hebei province, China (ZJK)]. And the particle swarm optimization and optimal water allocation model were used to select the best crop distribution scenarios for improving the GRCC. The results showed that IncMSE index (random forest) for each influencing factors ranging from ? 3.4–8.9, indicating that crop distribution is the most important factor affecting the GRCC. Therefore, changing the crop distribution is the key factor to improve the GRCC in ZJK. The results of optimizing crop distribution scenarios showed the total water use for optimized crop distribution O26 (potato and cabbage planting area were 36,885 and 362,936 ha) was 713,701,500 m3, which was reduced by 14% compared to base scenarios in 2016. Furthermore, the GRCC index (D) has decreased by 53%～83%, which means the groundwater resources would be sustainable by using this crop distribution with irrigation quotas are 900 and 1875 m3/ha respectively. The results can provide decision-making references for sustainable use of groundwater resources in groundwater over-exploitation regions.
查看更多>>摘要：? 2022 Elsevier B.V.New Rice for Africa (NERICA) was reported to have higher exudation and transpiration rates, above ground dry matter at heading than Japanese cultivars. Information on the expression of their gas exchange attributes and water balance under repeated cycles of water deficit at reproductive stage is unknown. This investigation tested the hypothesis that variation in leaf gas exchange and energy attributes of NERICA rice under repeated cycles of water deficit at reproductive stage would affect their performance under field conditions. Repeated cycles of water regimes (irrigation and water deficit) at reproductive stage were imposed on eight NERICA rice (NERICA 1–8) and checks (CG14, WAB56–104 and IR64). Water regimes were assigned to main plots and rice cultivars to sub-plots using randomised complete block design with three replicates. Drought-tolerant NERICA 4 and 7 had significantly higher relative water content, stomatal conductance, leaf photosynthetic rates with the least canopy temperature than others. A converse pattern was observed in the drought-susceptible IR 64. Grain yield of NERICA 4 and 7 was significantly higher than that of IR 64. These results suggested that improved water and energy status observed in NERICA 4 and 7 could have been responsible for its better performance than IR 64.
查看更多>>摘要：? 2022Increased water demands and drought have resulted in the need to provide data to guide deficit water management decisions in irrigated maize (Zea mays L.) for grain production. The objective of this study was to develop relationships between maize grain yield and maize water use (ETc, crop evapotranspiration) under low and high nitrogen (N) input systems on a soil type (silt loam) common to maize production in the arid Northwest U.S. The treatments consisted of two N inputs (0 and 246 kg N ha-1 year-1, -N and +N, respectively) and four water input treatments ranging from 100% to 25% of full irrigation. The full irrigation treatment was 20% less than evapotranspiration model calculated crop use (ETm), indicating that crop coefficient (Kc) values may need to be adjusted for maize in the arid Northwest U.S. There were no grain yield response differences between N input treatments in 2017 but during 2018 and 2019 (treatments on same plots), ETc versus grain yield relationships were different for the -N and +N treatments. Crop water production functions were developed using quadratic relationships between ETc and maize grain yield. The range of grain yield across all years and treatments were 15.03–7.23 Mg ha-1. The range of crop water productivity (CWP) across all years and treatments were 1.6–2.6 kg m-3. The ETc at maximum CWPs across all years and treatments had a range of 60–71% of ETm. These relationships are valuable to understanding maize response over a range of water availability and in developing tools to assess future production under water shortages.
查看更多>>摘要：? 2022 Elsevier B.V.Agriculture has by far the largest water footprint of human activities. Improving the water productivity of crop production is key to enhancing both water and food security. Irrigation is a significant pressure on water resources in the arid region of Northwest China. Here, we examine optimizing the regional cropping distribution within the Heihe River basin for achieving the dual goals of improving productivity and reducing irrigation water demand. The Soil and Water Assessment Tool (SWAT) and a cellular automata model are employed to model the processes of cropping pattern changes. The optimization takes the maximum of crop water productivity (CWP), the maximum economic water productivity (EWP) and the maximum nutrient water productivity (NWP) as the objective function. The model optimizes the spatial distribution of six crops including corn, spring wheat, spring barley, spring canola-Polish, alfalfa and upland cotton. Results show that under the premise of considering food security, the maximization of water productivity for CWP, EWP, and NWP, leads to the reduction of corn planting area and the eastward shift of corn planting region. A significant decrease in the proportion of wheat planting occurs in the objective of EWP maximization, while the planting proportion of barley and canola increased significantly. All three optimization objectives yield cropping distributions that reduce the irrigation water demand of cultivated land and improve the water productivity of the basin, among which maximizing CWP scenario has the greatest water-saving intensity. Furthermore, from the perspective of ecosystem services, the cropping distribution of maximizing EWP is more reasonable for the basin. Different cropping change scenarios provide effective references for decision makers to make a reasonable cropping distribution in the region.
查看更多>>摘要：? 2022 Elsevier B.V.The importance of stevia (Stevia rebaudiana) is increasing rapidly as a potential industrial crop throughout the world. Soil-moisture and nitrogen (N) are the key components for agricultural productivity. However, the information on the effects of availability of soil moisture and N dose on the growth of stevia, N dynamics in the plant and soil, and NUE is limited. Thus, a field study involving three soil-water regimes (irrigation schedule at 20–75 kPa) and five different levels of N (0–140 kg ha?1) was conducted. Results showed that the dry leaf and total steviol glycosides (SGs) yield of stevia was found maximum with the irrigation at 50 kPa. At harvest, the plants irrigated at 50 kPa produced 26.9–32.5% higher dry matter over limited application of water (75 kPa). The N at 105 kg ha?1 registered maximum leaf yield (2.59 and 2.37 t ha?1) and N uptake (83.23 and 74.73 kg ha?1). The higher dose of N (140 kg ha?1) did not enhance dry leaf and total SGs yield compared with N at 105 kg ha?1. The low apparent N-recovery and agronomic N-efficiency at higher doses of N indicate higher accumulations of N into the environment. The soil N-balance sheet indicates that the maximum N has been harvested with the higher N under water limiting conditions. Thus, it can be concluded that the irrigation at 50 kPa in combination with N at 105 kg ha?1 could improve leaf and total SGs yield, N uptake, and NUE of stevia without deteriorating soil health.
查看更多>>摘要：? 2022 Elsevier B.V.Water cycling within agricultural watersheds includes high uncertainty because of natural and anthropogenic factors (e.g., cultivation practices). Remotely sensed evapotranspiration products (RS-ET) have been adopted as an additional constraint on watershed modeling to enhance the accuracy of water cycling predictions while reducing uncertainty. However, plant parameters affecting evapotranspiration (ET) in watershed models are poorly calibrated without the use of appropriate constraints. The goal of this study is to assess the predictive uncertainty of the Soil and Water Assessment Tool (SWAT), depending on the inclusion or exclusion of annual crop yield as an additional constraint for an agricultural watershed. We analyzed the simulated results with acceptable performance measures depending on a varying degree of model constraints: one constraint (streamflow), two constraints (streamflow and RS-ET) and three constraints (streamflow, RS-ET, and crop yield). The three performance measures used were Nash-Sutcliffe Efficiency (NSE), Percent bias (P-bias), and Kling-Gupta Efficiency (KGE). As the number of model's constraints increased, the number of acceptable parameter sets were substantially reduced from 180 (acceptable for streamflow) to 116 (acceptable for streamflow and RS-ET) and 2 (acceptable for streamflow, RS-ET, and crop yield). In addition, overall model performance measures for ET were greatest in the simulation results with three constraints representing 0.02–0.2 and 0.04–0.05 greater NSE and KGE values than those of one constraint and two constraints, respectively. The parameter set with the best ET performance measures was also acceptable for predicting crop yield. Based on these results, we conclude that this crop yield data can be adopted as a model constraint for agricultural watersheds to reduce model uncertainty in ET simulations and to increase model prediction accuracy.
查看更多>>摘要：? 2022 Elsevier B.V.To further explore the performance of the newly proposed crop water stress indicator - the Mean Value of Gaussian Distribution of Excess Green index (MGDEXG) for maize canopy in RGB imagery, studies were conducted in two maize fields with different irrigation levels during the 2015 and 2019 growing seasons. Specifically, the effects of spatial resolution of RGB images collected by both ground and UAV platforms, and segmentation scale of UAV RGB orthophoto on the performance of MGDEXG were investigated, and MGDEXG maps were derived based on UAV RGB orthophoto to monitor maize water status and its inter-field variability. The results show that when the spatial resolution of ground RGB images (2.4 mm) was resized by bilinear interpolation algorithm to 4.8, 9.6, 19.2, 38.4, and 76.8 mm, similar water estimation performances of MGDEXG were observed when compared to the crop water stress index (CWSI), with R2 values ranging 0.80–0.83. However, the processing time per RGB image with 2.4 mm spatial resolution was greatly reduced from 232.26 s to 0.32 s when the resolution was reduced by 32 times, providing a better opportunity to obtain MGDEXG in real-time. When UAV RGB images with two spatial resolutions of 2.7 mm and 14.7 mm were adopted, a poor water stress estimation performance was observed for the lower resolution with R2 of 0.62 and RMSE of 0.12 mol·m-2·s-1 for the maize stomatal conductance. The possible reason could be the errors introduced during the mosaicking process. When segmentation scales of 2 m x 2 m, 4 m x 4 m, 6 m x 6 m, 8 m x 8 m, 10 m x 10 m, and 12 m x 12 m were adopted to crop UAV RGB orthophoto, similar results were also observed. Finally, MGDEXG maps were derived from UAV RGB orthophoto. Overall, this study demonstrated that the water stress estimation performance of MGDEXG index was not affected by image spatial resolution and statistical scale, and MGDEXG maps could be successfully acquired by a UAV RGB remote sensing platform with the advantages of low cost and easy to be adopted by users.
查看更多>>摘要：? 2022Agriculture-heavy alluvial aquifer regions around the world have experienced severe groundwater declines due to irrigation demand. This consequence has been observed in the United States in the latter half of the 20th century, notably in the Central Valley of California and in the Mississippi River Valley. In some portions of the Mississippi River Valley, such as the Cache River Critical Groundwater Area (CRCGA) of northeast Arkansas, drawdown has exceeded 30 m and portends aquifer depletion in the near future. In addition to adopting surface-water storage and irrigation efficiency methods, farm-scale managed aquifer recharge (MAR) with infiltration galleries (IG), gravel-filled trenches designed to move surface water into the aquifer, may be a useful tool for reducing declines. Low-permeability surface deposits, which limit and create significant variation in natural recharge across the region, also control the placement of MAR systems. It is therefore critical to understand the variability of surface deposits, as well as underlying aquifer properties, to best plan the placement, design, and operation of such systems. This study aimed to characterize surface and upper aquifer conditions to assess the feasibility of IG in the central CRCGA. Available well logs were used to interpolate the approximate thickness of surface deposits and identify thinner areas. Approximately 37% of the study area has less than 5 m of confining material at the surface and included 28 existing reservoirs that could act as recharge water sources. Guided by this mapping effort, geophysical and sediment surveys were conducted at selected sites. The upper unsaturated alluvial aquifer of fine silty-sand had estimated hydraulic conductivities of 0.20–2.79 m d?1. These results are promising for the implementation of farm-scale IG in the study region and suggest that small MAR systems could be a useful tool for groundwater management in other agricultural aquifer systems given the proper placement.
查看更多>>摘要：? 2022Subsurface (tile) drainage, while necessary for viable agricultural crop production in the humid, poorly drained regions of the world, has been linked to offsite nutrient transport, culminating in harmful algal blooms and hypoxia in downstream waterbodies. Drainage water management (DWM), also known as controlled drainage, has been promoted as a method to reduce nitrogen (N) and phosphorus (P) loss from field scale tile drainage; however, subsequent changes in surface runoff and associated water quality have not been explored. Four years of surface and subsurface discharge, N, and P loss from two sets of paired field sites in northwest Ohio, USA were evaluated using a before-after control-impact (BACI) design to quantify the impact of DWM. Mean event surface runoff was greater (significant at one site) under DWM while tile drainage discharge was less at both sites but not significant. There was no significant difference in surface nitrate-N (NO3--N) loss; however, significant reductions in tile NO3--N loss under DWM were measured at both sites. Similar to discharge, dissolved reactive P (DRP) loss measured in surface runoff was greater under DWM (significant at one site), while no significant differences were noted in mean event tile drainage DRP loss. Total P (TP) surface runoff losses were significantly greater under DWM at the site with significantly greater surface runoff, while DWM reduced tile drainage TP loss at only one site. These findings suggest that DWM reduced tile NO3--N loss, while also highlighting that any benefit from DWM with respect to tile DRP or TP loss could be negated in part by increased surface losses. Furthermore, these findings emphasize the need to understand the natural resource concern to which the practice is targeted and also call for additional research on DWM implementation that includes surface runoff across a range of soil textures, cropping management, and climates.
查看更多>>摘要：? 2022 Elsevier B.V.The raised and sunken bed (RSB) land configuration was tested and evaluated during 2017–2020 for promoting crop diversification and intensification, enhancing water and crop productivity, and testing the economic variability of the farmers of North-east India. Being situated in sub-tropics, the study area received an average annual rainfall of 1905 mm. Water accumulated in the sunken beds was used for irrigating crops in the raised beds. The results indicated considerable improvement in cropping intensity, productivity, employment, and income under RSB system in comparison to farmers’ practice (FP) of rice monocropping system. Various cropping sequences such as broccoli-blackgram, cabbage-blackgram, cauliflower-blackgram, tomato-cowpea (fodder), chilli-greengram, potato-blackgram, pea-greengram etc. in raised beds and rice-rice sequence in sunken beds were possible under RSB land configuration to diversify the rice monocropping system. The rice equivalent yield (REY) of the cropping sequences under RSB ranged between 8.9 and 43.5 t ha?1 over only 2.7 t ha?1 under FP. The employment generation and crop production were enhanced by over 10 times (942%) and 4 times (336%), respectively under RSB over the FP. Similarly, water productivity and production efficiency were enhanced by 2.0–31.0 and 1.5–13.8 times, respectively through various cropping sequences compared to rice monocropping (FP). The various cropping sequences under RSB land configuration enhanced the B:C ratio by 75.5–513.2% over the FP producing a net income ranging from USD 657.7 to USD 5890.1 ha?1 against only USD 26.1 ha?1 under FP.
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