灌溉水盐度和施氮量对棉花根系分布影响研 究简

 通过田间小区试验,研究了不同灌溉水盐度和施氮量对滴灌棉花根系分布的影响。试验设置3种灌溉水盐度;0.35、4.61和8.04 dS·m^-1（分别代表淡水、微咸水和咸水三种灌溉水类型）;施氮量为0、240、360和480 kg·hm^-2。结果表明,按质量计,棉花的根主要分布在0~20 cm,此部分占根总质量的85%~90%。微咸水和咸水灌溉棉花根的总质量显著降低,分别较淡水灌溉减少10%和36%,尤其在土壤表层0~20 cm和下层60~100 cm显著降低;施用氮肥可以显著增加棉花根的质量。以长度计,棉花根集中分布在0~60 cm,此部分占总根长的87%~96%;60 cm以下根长密度明显降低。微咸水灌溉棉花根长密度最大,其次是咸水,淡水灌溉最低;淡水灌溉下,根长密度随施氮量增加显著降低;微咸水和咸水灌溉下,根长密度随施氮量增加呈先增后降趋势,其中施氮240 kg·hm^-2最高。棉花根表面积表现为微咸水>淡水>咸水,平均根直径为微咸水>咸水>淡水,而不同灌溉水处理间根体积的差异不显著。随着施氮量的增加,根表面积、根体积和平均直径均显著降低。     

Soil‐Based Vegetation Technique to Quantify Effects of Rhizospheric Soil Osmotic and Matric Water Potentials on Crop Salt Tolerance

In saline soils, plant water supply is the most critical growth factor. To better understand water supply and growth of soil‐grown crops, research should focus on root water uptake in saline soils. Plant water supply and growth is complex. One has to consider, simultaneously, soil and plant parameters: (i) the soil physical parameters texture; pF curve; osmotic, matric and total water potential; salinity at the soil/root interface; and bulk soil salinity; and (ii) the plant parameters root mass and rooting density; root morphology; transpiration; and shoot growth. Technical devices for direct and simultaneous measurement of all parameters are not yet available. This study presents a vegetation technique (VeTe) that permits to determinate required data from continuous measurement of pot water losses and by indirect calculation. The VeTe was tested using young rape (Brassica napus, cv. Lingot) as the model plant, growing in a silty soil. Rape was selected for its efficient root system to explore soil determined growth factors. Basically, the VeTe requires two vegetation phases: a pre‐cultivation phase, and an experimental phase. The objective of the first phase is to grow young plants that are homogenous in their shoot and root development through well‐controlled water management. Varying rooting densities of soils are performed when plants are pre‐cultivated in different soil volumes. The experimental phase starts when plants are irrigated with water of different salt concentrations up to soil water contents of 30 vol.%. During the experiment, plants were grown under well‐controlled, climatic conditions, and pot water losses were measured bi‐hourly. Measurement of continuous water losses serves to calculate soil moisture contents, derive osmotic and matric heads and their impact on plant transpiration. The proposed technique provides a means for quantitatively studying the combined impacts of soil osmotic and matric stresses on water uptake by crops differing in their root morphologic traits at different rooting densities.     

微咸水膜下滴灌土壤水盐运移研究进展

覆膜灌溉、滴灌和利用微咸水灌溉是极具生命力的3种节水灌溉方式。将三者结合的微咸水膜下滴灌是一项复杂的系统工程,对土壤和作物存在潜在的威胁。因此,近30年来国内外学者对膜下滴灌土壤水盐动态、微咸水灌溉影响效应,以及膜下滴灌土壤水盐运移模型进行了细致研究,并取得大量成果。但是,作物-水盐之间相互作用机理的探寻、田间尺度的盐分迁移转化参数问题,以及如何结合当地土壤水土资源状况,建立安全高效的膜下微咸水滴灌的土壤水盐调控技术体系和灌溉模式,并在区域上推广应用等问题亟待解决。     

Establishment of a crop evapotranspiration calculation model and its validation

In order to contribute knowledge on the method used to calculate the actual crop evapotranspiration, soil, crop, atmosphere, and water spatial structure were integrated into a complete system. Based on the energy balance equation and aerodynamic equation, the meteorological data was reduced and the crop physiological parameter was increased, then the crop evapotranspiration calculation model under natural conditions was derived. The crop evapotranspiration calculation model was verified by the water balance formula using data generated from corn, potato, and flue-cured tobacco grown under field conditions for three consecutive years from 2017 to 2019. The results showed that: from 2017 to 2019, the average root mean square error for measured and calculated evapotranspiration of corn, potato, and flue-cured tobacco at different growth times were 0.5948, 0.4753, and 0.3326, respectively, the mean deviation, mean absolute error, and mean relative error were small, and the coefficient of determination and consistency index were both greater than 0.9100. The measured and calculated crop evapotranspiration of the selected crops increased at first and then decreased gradually as the crops matured, and finally decreased to harvest evapotranspiration, showing a parabolic trend. The crop evapotranspiration calculation model not only reflects the actual evapotranspiration of crops at different growth time but also reflects the change law of actual crop evapotranspiration. The model does not need the correction of soil moisture content, irrigation method, and crop coefficient and can directly calculate the actual crop evapotranspiration. It has the characteristics of consistency between the calculated value and the measured value, strong applicability, simple calculation process, and high accuracy and has the best effect on monitoring soil moisture and crop water shortage sensitivity. The model is significance in that it guides for monitoring soil moisture, determining actual crop evapotranspiration, crop water shortage index, and high yield and efficiency under water-saving conditions.     

基于咸水处理和精准灌溉相结合的优势分析

咸水淡化技术是开发利用海洋资源最合理的方式。文章从咸水直接灌溉带来的土壤盐渍化危害入手,概述了咸水处理与精准灌溉的意义,介绍了微咸水淡化流程和精准灌溉流程,提出了微咸水处理及精准灌溉的结合方式,展望了咸水淡化和节水灌溉的发展趋势,并分析了制约咸水淡化技术发展的能源和工艺2个因素。本研究得出,节水灌溉技术未来将集远程灌溉管理和综合调控分析于一体,真正实现智能化灌溉管理。将太阳能技术与纳滤技术相结合会创造广阔的市场前景,纳米颗粒膜和光热转化碳纤维等材料将是海水淡化研究的热点。因此,咸水淡化技术与精准灌溉相结合,其资源利用效率将大幅提高,土壤环境亦会得到极大改善,与未来生态科技的发展趋势将更加契合。     

Climate-smart crops: key root anatomical traits that confer flooding tolerance

Plants require water, but a deficit or excess of water can negatively impact their growth and functioning. Soil flooding, in which root-zone is filled with excess water, restricts oxygen diffusion into the soil. Global climate change is increasing the risk of crop yield loss caused by flooding, and the development of flooding tolerant crops is urgently needed. Root anatomical traits are essential for plants to adapt to drought and flooding, as they determine the balance between the rates of water and oxygen transport. The stele contains xylem and the cortex contains aerenchyma (gas spaces), which respectively contribute to water uptake from the soil and oxygen supply to the roots; this implies that there is a trade-off between the ratio of cortex and stele sizes with respect to adaptation to drought or flooding. In this review, we analyze recent advances in the understanding of root anatomical traits that confer drought and/or flooding tolerance to plants and illustrate the trade-off between cortex and stele sizes. Moreover, we introduce the progress that has been made in modelling and fully automated analyses of root anatomical traits and discuss how key root anatomical traits can be used to improve crop tolerance to soil flooding.     

Saline Drainage Water, Irrigation Frequency and Crop Species Effects on Some Physical Properties of Soils

This field study evaluated the effects of water quality, irrigation frequency and crop species on some physical properties of soils. The experiment had a split-split-plot design, with three irrigation water qualities (normal water, drainage water and a 1 : 1 mixture of freshwater and drainage water) as the main treatments, two irrigation frequencies (at 7- and 14-day intervals) as the subtreatments and two crops (barley and alfalfa) as the subsubtreatments. The soil infiltration rate was highest in the barley plot receiving freshwater irrigation at weekly intervals. The lowest soil infiltration rate was found in alfalfa plots receiving saline irrigation water at 14-day intervals. Bulk density and proportions of micropores [pore radius (r) < 1.4 µm] were higher and the proportion of macropores (r > 14.4 µm) was lower in barley than in alfalfa. Saline irrigation caused the greatest decrease in total porosity. The soil infiltration rate was higher with more frequent irrigation, and was highest in alfalfa plots receiving freshwater irrigation. The decrease in soil bulk density and infiltration rate was greater with saline drainage water, irrespective of the crop grown and the irrigation frequency.     

Comparative Effect of Nitrogen Sources on Maize under Saline and Non-saline Conditions

The main objective of this study was to compare the relationship between biomass yield and nutrient uptake in salt-stressed maize ( Zea mays L.) following nitrogen (N) nutrition in a greenhouse. Three forms of N were applied, each at the rate of 100 kg ha⁻¹: urea-N, nitrate-N, 1/2 urea-N + 1/2 nitrate-N (mixed-N) and no N application (control). Maize was grown as a test crop for 6 weeks. All N sources greatly stimulated crop growth and nutrient uptake compared with the control. The biomass (shoot and root) of maize was significantly greater in mixed-N treatment than in single sources in saline soil whereas it varied in the order of urea-N > mixed-N > nitrate-N > control in non-saline soil. Under both soil conditions, the concentration of Ca, Mg and Na in shoot was highest in nitrate-N treatments while that of K was highest in the control. Shoot nitrogen concentration was not significantly different among N sources under non-saline treatment, whereas under saline conditions, the concentration varied markedly in the order of nitrate-N > urea-N > mixed-N > control. The mineral concentrations in the shoot increased under salt treated soil when compared with non-saline soil. The ratios of Na/K, Na/Ca and Na/Mg were also higher under salt stress due to higher accumulation of Na ion in the shoot. Among N-fertilizer sources, Na/Ca and Na/Mg ratios were highest in control whereas Na/K ratio was the highest in nitrate-N treatment. The lowest cation ratios were noted in mixed-N-treated plants under both soils. Regression analysis showed that maize biomass was related to N concentration by the following equations: Y = −4.54 + 0.97N for the non-saline soil and Y = 0.89 + 0.25N for the saline soil. Nitrogen use efficiency for non-saline soil exceeded that of saline soil by 15 %.     

Development and Testing of Root Effectiveness Function for Soil Water Uptake

For soil water uptake studies under cropped conditions, root effectiveness for soil water absorption is of great significance. For development of root effectiveness function, information on the age of roots present at any soil depth at any time during the crop growth period is needed. For estimation of root age and root effectiveness function, a methodology has been developed. Wheat crop was used as a test crop. It has been observed that root effectiveness for water uptake remains constant during the early period of root growth and thereafter it decreases exponentially with root age. The application of the proposed root effectiveness function was tested successfully using macroscopic model of soil water dynamics which yielded 7 .83 per cent variation between observed and simulated soil water content on overall basis in the crop root zone for the entire crop growth season.     

Spatial and temporal changes to the water regime of a Mediterranean vineyard due to the adoption of cover cropping

The use of cover cropping is currently increasing in vineyards but its development remains hampered in Mediterranean regions because of the possibility of severe competition for resources. However, recent studies on intercropping in vineyards have shown that in some situations, water stress may not be greater than that prevailing in bare soil vineyards. Over a 4-year period, we studied the effects of introducing a cover crop in terms of temporal and spatial (i.e. row vs. inter-row) changes to the water regime of a Mediterranean vineyard. The experiments compared the water dynamics prevailing under three different treatments: a perennial cover crop, annual cover crop or the use of chemical weed control.A compensatory growth of the grapevine root system was revealed, thus partly prevented direct competition for resources between it and the intercrop. The rooting of a permanent cover crop was deeper than that of an annual crop, with a higher root density. Consequently, the soil compartment dried by the cover crop was larger and the grapevine was forced to explore deeper soil layers. In the presence of a cover crop on the inter-row, the grapevine also concentrated its root system below the row and dried out this soil compartment more intensively. Overall, associating grapevine with a cover crop led to a spatial distinction of soil zones exploited by the two species. The present study provides evidence that this spatial shift mainly resulted from a temporal shift in the dynamics of resource uptake by the associated species. Indeed, cover crops began to take up water before grapevine budbreak and had almost completely dried out the soil compartment they explored before grapevine water uptake became significant. This led the grapevine to modify its rooting and explore other soil zones. This phenomenon is possible in deep soils and limits competition for water between the grapevine and cover crop. Such competition is also reduced because of better soil water replenishment during the winter in the presence of a cover crop. Nevertheless, our experiments showed that this additional water mainly benefited the intercrop and did not totally compensate for transpiration by the grass cover.In conclusion, this work shows how cover cropping can spatially and temporally modify the water regime of a vineyard, and how grapevine can partially adapt to limit water competition under certain conditions. These findings provide a clearer understanding of the water dynamics prevailing in such a system, and an opportunity to model these dynamics.     

磁化水灌溉对农作物生长发育影响的研究进展

磁化水处理应用于农作物的生产实践是一个比较特殊的领域,国内外科研人员在开发磁化水的基础上开展了磁化水对农作物生长发育影响的诸多研究,比较了磁化水与普通水灌溉对种子发芽、秧苗生长素质、田间相关农艺性状及土壤理化性质影响的异同,表明磁化水对水稻生长发育调控和土壤改良效应有一定的影响。通过系统总结,发现磁化水对水稻及其他农作物表现出的差异主要集中于土壤特性、生长指标、叶片叶绿素含量、根系性状、产量及品质方面,同时磁化水灌溉影响水稻及其他农作物的生理特性。研究结果为磁化水灌溉在农作物生产中的推广应用提供参考依据。     

作物对干旱胁迫的响应机制及提高作物抗旱能力的调控措施研究进展

干旱是影响作物生长发育和产量的最主要非生物胁迫之一,在气候变化背景下,作物遭受干旱胁迫的风险越来越大。为了应对干旱,作物表现出一系列的抵御机制,包括形态特征和生理生化（抗氧化酶、渗透调节物质、内源激素）特性改变。本研究从上述2个方面总结了作物对干旱胁迫的响应机制,并对提高作物抗旱能力的调控措施进行了论述,主要包括：（1）筛选抗旱性品种,促进对深层土壤贮水的吸收利用;（2）地面覆盖,有利于降低土壤蒸发,增加土壤含水量;（3）节水灌溉技术,如微喷灌、滴灌等灌溉方式能实现少量多次灌溉,根区局部灌溉有利于调节气孔关闭,减少奢侈蒸腾,降低土壤蒸发;（4）抗蒸腾剂,在作物枝干及叶面表层形成超薄透光的保护膜,抑制作物水分过度蒸腾;（5）植物生长调节剂,调控植物生理代谢,增强抗旱性;（6）纳米肥料,改变作物生理生化反应,促进植株生长发育;（7）生物炭,有利于土壤通气保水,改善土壤的物理性质和土壤的持水能力。本研究系统地对以上7种措施提高作物抗旱能力的作用机理、应用前景及存在问题进行了论述,以期为应对干旱胁迫提供理论依据和技术参考。     

一种水肥气高效耦合灌溉系统的设计与试验研究

本研究旨在解决传统灌溉农业的“水氧矛盾”和根系的“向水追氧”两大农业难题,应用现代水肥耦合和增氧灌溉技术,设计了一种水肥气高效耦合灌溉系统。通过应用灌溉系统对水稻、黄瓜等作物的栽培试验证明：相比于常规灌溉方式,水、肥、气耦合灌溉能促进作物根系生长和提高根系活力,使其能最大限度地从土壤中吸收水分和养分,进一步挖掘和提高作物自身生产力,提高水肥利用效率,增产提质,同时也为从根源上缓解农业面源污染提供一种新途径。     

局部灌水条件下不同根区在作物吸水中的作用

采用分根装置,在均匀灌水、固定部分根区灌水和根系分区交替灌水3种方式下,分期测定玉米的耗水量、两个1/2根区及整个根区的土—根系统水分传导与土壤含水量,研究各个根区在作物水分吸收中的作用。结果表明,3种灌水方式下,玉米耗水量与全部根区和灌水区土-根系统水分传导间均存在密切的正相关关系。均匀灌水条件下,1/2根区水分传导约占全部根区水分传导的一半;固定灌水条件下,灌水区占全部根区水分传导的比例远大于非灌水区,与全部根区接近。交替灌水条件下,两个根区对全部根区水分传导的贡献呈交替变化,其非灌水区占全部根区水分传导的比例较之固定灌水明显增大。全部根区土-根系统水分传导与灌水区土壤含水量明显相关,灌水区土壤含水量决定了整株作物的水分吸收情况。交替灌水的非灌水区从土壤到根系仍有一定的水分传输作用,而固定灌水的非灌水区使全部根区的土—根系统水分传导降低。     

不同灌水处理对盐渍土壤中玉米生长发育 及水盐热变化的影响

通过盐渍土壤盆栽玉米种植试验,对常规灌溉、固定灌溉、交替灌溉3种灌水方式下玉米的生长发育及水分、盐分、温度的变化情况进行了研究。结果表明:不同的灌溉处理对玉米生长发育及水分、盐分、温度变化的影响较大。株高和叶面积的长势是常规灌溉>交替灌溉>固定灌溉;生育期水分利用率和主根生长条数是交替灌溉>常规灌溉>固定灌溉,根冠比是交替灌溉>固定灌溉>常规灌溉;随着土层深度的增加温度呈减小的趋势,且对3种灌水方式都有A灌水水平的温度低于B灌水水平的温度;随着土层深度的增加体积含水率呈增大的趋势;由于蒸发和灌水交替进行,电导率在土层深度上呈现出多变的特点。     

Growth,Development and Yield of Crambe Abyssinica Under Saline Irrigation in the Greenhouse

Salinity is one of the major factors limiting agricultural productivity in arid and semi‐arid regions. Saline areas around the world are increasing and sources of fresh water are decreasing. The increasing importance of the use of brackish water to supplement regular irrigation has demonstrated a need for finding new potential plants with tolerance to irrigation with saline water which can be used in industrial agriculture. The aim of this study was to determine whether irrigation with brackish water of Crambe Abyssinica, a plant commonly used for industrial oil production and for ornamental purposes and with high economical value, especially in Central Asia and the Aral Sea region, is feasible. One more goal was to study how it influences growth and development, seed and oil yield and some physiological parameters such as photosynthesis, transpiration, chlorophyll content, osmotic potential and accumulation of fresh and dry weight. The effects of three salinity levels, 3, 6 and 9 dS m^?1, were investigated in a greenhouse experiment during two consecutive years. Results of this study showed that growth of Crambe abyssinica in arid zones and irrigation with mild saline water up to EC 6 dS m^?1, mostly common in these areas is feasible, suggesting tolerance to moderate salinity levels and feasibility of its culture in areas of the Aral Sea with adequate salinity levels. Consequently, in spite of the fact that biomass and seed yield were significantly decreased in plants irrigated with brackish water, Crambe abyssinica might be cultivated as an alternate source of green biomass and for industrial vegetable oil under conditions not suitable for conventional plant production.     

Root and Shoot Development of Phaseolus vulgaris L. (French Beans) as Affected by Soil Moisture and Fertilizer Potassium

The development of an extensive root system enables plants to overcome water stress. However, there is little information on the response of food legumes to soil moisture, especially during early growth, which determines crop establishment. Thus, an experiment was conducted under controlled conditions to identify the effect of soil moisture and fertilizer potassium on root and shoot growth of french beans ( Phaseolus vulgaris L.) seedlings. The seedlings were grown in a sand medium under a high and low soil moisture regime and with 0.1, 0.8 or 3.0 mM potassium.
Root lengths, dry weights and numbers of root hairs were greater under low soil moisture conditions. Potassium increased root growth irrespective of soil moisture regimes. The impact of potassium on root length was more pronounced under a high soil moisture regime. In contrast, potassium increased root dry weights and root hairs to a greater extent when plants were grown under dry conditions. The lack of adequate soil moisture increased specific leaf weights, and this phenomenon was reduced by the application of potassium. Shoot:root ratios also showed a similar phenomenon. The development of an extensive root system by french bean seedlings under dry conditions to extract a greater quantity of available soil moisture fur establishment and plant growth and the ability of potassium to promote this phenomenon is presented in this study.     

SHORT COMMUNICATION: Effect of Salt Stress on Peruvian Germplasm of Chenopodium quinoa Willd.: A Promising Crop

Soil salinity is a major problem in today’s agriculture. Quinoa has become an important crop because it exhibits high levels of salinity tolerance. In addition, its seeds contain an excellent balance of carbohydrates, lipids, amino acids and proteins for human nutrition. The quinoa germplasm includes almost 2500 accessions, some of which have been tested under salt stress. Here, we report the effect of NaCl on the germination of 182 previously untested accessions. When seeds were irrigated with saline water at 30 dS m^?1 EC, the stress appeared to be too high: all accessions showed less than 60 % germination. In contrast, irrigation with 25 dS m^?1 EC saline water allowed over 60 % germination in 15 accessions. These latter accessions’ agricultural traits were then evaluated. The overall coefficients of variation indicated that quinoa genotype and salt treatment dramatically influence root dry mass per plant, but do not noticeably affect the length of the plant’s life cycle. Unexpectedly, salt treatment resulted in increased plant height, leaf dry mass and grain yield. Using Euclidean distance for the simultaneous selection of these five agricultural traits, accessions 100, 136, 127 and 105 proved to be the best performing genotypes under salt stress.     

Water Relations and Transpiration of Quinoa (Chenopodium quinoa Willd.) Under Salinity and Soil Drying

Drought and salinity are the two major factors limiting crop growth and production in arid and semi‐arid regions. The separate and combined effects of salinity and progressive drought in quinoa (Chenopodium quinoa Willd.) were studied in a greenhouse experiment. Stomatal conductance (g_s), leaf water potential (Ψ_l), shoot and root abscisic acid concentration ([ABA]) and transpiration rate were measured in full irrigation (FI; around 95 % of water holding capacity (WHC)) and progressive drought (PD) treatments using the irrigation water with five salinity levels (0, 10, 20, 30 and 40 dS m^?1); the treatments are referred to as FI₀, FI₁₀, FI₂₀, FI₃₀, FI₄₀; PD₀, PD₁₀, PD₂₀, PD₃₀, PD₄₀, respectively. The measurements were carried out over 9 days of continuous drought. The results showed that increasing salinity levels decreased the total soil water potential (Ψ_T) and consequently decreased g_s and Ψ_l values in both FI and PD. During the drought period, the xylem [ABA] extracted from the shoots increased faster than that extracted from the roots. A reduction in Ψ_T, caused by salinity and soil drying, reduced transpiration and increased apparent root resistance (R) to water uptake, especially in PD₀ and PD₄₀ during the last days of the drought period. The reasons for the increase in apparent root resistance are discussed. At the end of the drought period, the minimum value of relative available soil water (RAW) was reached in PD₀. Under non‐saline conditions, Ψ_l decreased sharply when RAW reached 0.42 or lower, but under the saline conditions of PD₁₀ and PD₂₀, the threshold values of RAW were 0.67 and 0.96, respectively. In conclusion, due to the additive effect of osmotic and matric potential during soil drying on soil water availability, quinoa should be re‐irrigated at higher RAW in salt‐affected soils, i.e. before the soil water content reaches the critical threshold level causing the drop in Ψ_l resulting in stomatal closure.     

Biochar amendment of fluvio‐glacial temperate sandy subsoil: Effects on maize water uptake,growth and physiology

Coarse sandy soils have poor water retention capacity, which may constrain crop growth during drought. We investigated the effect of biochar amendment to subsoil on crop physiological processes and maize yield, comparing irrigated and drought conditions. A two‐year greenhouse experiment was conducted with one‐time application of straw biochar at concentrations of 0%, 1%, 2% and 3% (B0, B1, B2 and B3). Maize was planted twice in the same large pots one week and again 12 months after biochar application. Plants were fully irrigated until flowering; thereafter, half of them were subjected to drought. Our results indicate B2 and B3 increased soil water content at field capacity. Leaf water potential, stomatal conductance, photosynthesis and transpiration were maintained in B2 and B3 during the drying cycle in year one and in all biochar levels in year two. In the first year, B3 induced negative root geotropism and significantly reduced vegetative biomass under both irrigation schemes. Cob biomass was significantly reduced by B1 under full irrigation. In year two, B3 significantly increased cob biomass under drought. Nitrogen uptake was significantly reduced by B2 in year one, but increased significantly in B3 in year two. In both years, P uptake was significantly increased by B2 and B3. Furthermore, K uptake was significantly increased in B2 in year one and in all biochar treatments in year two. Overall, biochar improved water content of coarse sandy soil due to decreased bulk density and increased porosity after biochar amendment, consequently, improving crop physiological processes including transpiration and photosynthesis. Significant effects on yields tended to be more negative in the first year, and neutral to positive in the second year suggesting the enhancement of biochar effects with ageing. The positive effect in the second year shows biochar's potential for improving agriculture productivity in drought‐prone regions.