Higher performance through combined improvements in irrigation methods and scheduling: a discussion

Prior to the discussion on approaches to combine irrigation scheduling and water application practices, several farm irrigation performance indicators are defined and analysed. These indicators concern the uniformity of water distribution along an irrigated field and the efficiency of on-farm water application. Then, the analysis focus is on three main irrigation systems: surface, sprinkler and microirrigation. For each of these systems, the analysis concerns the main characteristics and constraints of the systems, more relevant aspects influencing irrigation performances, and approaches which could lead to a more appropriate coupling of irrigation scheduling and water application methods. Conclusions point out on the need for combined improvements in irrigation scheduling and methods, for expanding field evaluation of irrigation in farmers fields, for improved design of on-farm systems, and for quality control of irrigation equipments and design.     

Optimal furrow irrigation scheduling under heterogeneous conditions

In California, better farm water management practices are needed to meet the increasing water demands by competing water users (industrial, urban, wildlife, etc.), increasing environmental awareness and cost of water. Management can be improved through better irrigation scheduling and irrigation system designs. In this study, optimal furrow irrigation schedules, designs and irrigation adequacy were determined for heterogeneous soil conditions. The seasonal performance between optimal and full irrigation was compared. For the bean crop studied, the maximum return to water was achieved with the irrigation adequacies of 63, 59, 54, 49 and 50%, respectively, for irrigation intervals of 10, 12, 14, 18, and 21 days. An irrigation interval of 10 days with 63% adequacy gave the global maximum return to water. However, the Natural Resource Conservation Service recommended irrigation adequacy for homogeneous soil condition is 87·5%. For any given irrigation interval, optimal irrigation required less (48–63%) water than full irrigation. This also reduced both the deep percolation and runoff losses and caused a 31–43% increase in the application efficiency. Furthermore, loss in revenue due to yield reduction was less than the savings in irrigation cost, which resulted in higher (32–54%) net return to water under the optimal irrigation compared with full irrigation. These results indicate that the optimal irrigation strategy has potential not only for water conservation, but also for reducing non-point source pollution.     

BP网络在焉耆盆地土壤积盐影响因素分析中的应用

以焉耆盆地为例，采用BP网络技术，对土壤舍盐量与各种影响因素的关系作了初步定量评价，发现潜水矿化度和潜水位埋深是土壤舍盐量的最敏感因素，其次是灌区引水量、引盐量和地下水蒸发量，其中灌区引水量大是焉耆盆地土壤次生盐渍化加剧的最主要因素；而潜水位埋深是土壤脱盐最敏感的因素。焉耆盆地土壤次生盐渍化防治应从减少灌溉引水量和降低地下水位入手。     

Effect of improved cultural practices on crop yield and soil salinity under relatively saline groundwater applications

The salinity in the root zone increases with the application of relatively saline groundwater. Therefore, a limited water supply coupled with high pumping cost and salinity hazards, makes it more important than ever that irrigation water be used efficiently and judiciously. In the present study, farmer's practices of irrigation application methods (Field 1) were compared with the water saving techniques (Field 2) for crop yield and salinization for two years with maize–wheat–dhanicha cropping pattern. For maize crop, regular furrow method of irrigation was used in Field 1 and alternate furrow method of irrigation was used in Field 2. For wheat experiments, basin irrigation method of water application was compared with bed and furrow method. For dhanicha, basin irrigation was applied in both the fields. The results showed that about 36% water was saved by applying irrigation water in alternate furrows in each season without compromising the maize crop yield. The salt accumulation in root zone in alternate furrow field was less than that in regular furrow field. The salinity level near the surface increased substantially in both the fields. The water saving in wheat crop under bed and furrow was 9–12% in both seasons. The salinization process in both fields during wheat crop was almost same except redistribution of salts throughout the root zone in basin field of wheat. The salinity developed in root zone during two major growing seasons was leached in monsoon.     

The adoption of improved irrigation technology and management practices—A study of two irrigation districts in Alberta, Canada

Irrigation is by far the largest consumer of water in Alberta. The government is therefore dependent on this sector to achieve water savings for reallocating water to other sectors. Hence, a major objective of a recent government strategy is to see an increase in water efficiency and productivity of 30%. A survey of two irrigation districts was undertaken to determine the measures irrigators have taken and plan to take in the future to improve irrigation technologies and management practices to enhance water use efficiency and which factors facilitate or impede the adoption of such measures. As anticipated, the adoption rate varied between the two districts as a result of differences in production characteristics. The major drivers of adoption were to ensure security of water supply during drought, to increase quantity and quality of crops, and to save cost, while the major impediments were financial constraints and physical farm conditions. It seems that most feasible technological improvements have been implemented and considerable financial improvements or subsidies will be necessary to encourage a significant increase in adoption. There seems to be considerable scope for improvement through the adoption of better management practices. Considering that farmers in the two irrigation districts also have modest plans to adopt improved management practices, promotion and education campaigns that encourage new practices that involve minimal cash outlays might yield the greatest water savings in the future.     

The effect of an intelligent surface drip irrigation method on sorghum biomass, energy and water savings

Over the last few decades, precipitation has decreased as a result of climate change. This change increases crop water requirements, while irrigation water is wasted because of improper irrigation scheduling. Soil moisture sensors could be used to improve irrigation scheduling and save both water and energy. The objective was to study the energy and water savings, and the gross margin achieved, when using an intelligent surface drip irrigation method on sorghum bicolor (L.) Moench. In the years 2008 and 2009, a study was conducted at the farm of the University of Thessaly, Central Greece. A Class A evaporation pan and an automated frequency domain reflectometry soil moisture sensor were used for irrigation scheduling. Two treatments in four replications were organized in a randomized complete block design: (1) pan surface drip irrigation (PSDI100) and amount of water equal to 100 % of the daily evapotranspiration (ETd), as determined by a Class A evaporation pan, and (2) automated surface drip irrigation (ASDI100) and amount of water equal to 100 % of the ETd, as determined by an automated soil moisture sensor. The mean dry biomass production and the gross margin were greater in the PSDI100 treatment. The fully automated treatment remained profitable despite the high first costs. The mean water saving was 12.5 %, while the mean energy saving was 12.4 %, and the irrigation water-use efficiency was higher in the ASDI100 treatment.     

Irrigation with saline water: benefits and environmental impact

The shortage of water resources of good quality is becoming an important issue in the arid and semi-arid zones. For this reason the availability of water resources of marginal quality such as drainage water, saline groundwater and treated wastewater has become an important consideration. Nevertheless, the use of these waters in irrigated lands requires the control of soil salinity by means of leaching and drainage of excess water and salt. However, the leaching of salts, soil microelements and agro-chemicals can lower the quality of the drainage water in the irrigation scheme. The irrigation return flows with water or poor quality are a source of pollution of the surface water bodies situated downstream of the drainage outlet. Deep percolation could also contaminate the groundwater. Therefore, irrigation with saline water requires a comprehensive analysis even beyond the area where water is applied. The problem should be treated beyond the scope of the irrigation scheme, taking into consideration the groundwater and downstream surface water resources of the river basin. Consequently, the sustainable use of saline water in irrigated agriculture requires the control of soil salinity at the field level, a decrease in the amount of drainage water, and the disposal of the irrigation return flows in such a way that minimizes the side effects on the quality of downstream water resources. This paper describes the guidelines for a preliminary evaluation of the suitability of water for irrigation and the key factors for salinity control in lands irrigated with saline water. Options to improve the quality of the drainage water, strategies for the reuse of this water and alternatives for disposal of the outflow are also analysed. The final goal is to obtain sustainable agriculture and maintain the quality of the water resources in the river basin.     

Numerical evaluation of subsurface trickle irrigation with brackish water

In this study, an assessment for a proposed irrigation system in the El-Salam Canal cultivated land, Egypt, was conducted. A numerical model (HYDRUS-2D/3D) was applied to investigate the effect of irrigation amount, frequency, and emitter depth on the wetted soil volume, soil salinity levels, and deep percolation under subsurface trickle irrigation (SDI) of tomato growing with brackish irrigation water in three different soil types. The simulations indicated that lower irrigation frequency increased the wetted soil volume without significant increase in water percolates below the plant roots. Deep percolation decreased as the amount of irrigation water and emitter depth decreased. With the same amount of irrigation water, the volume of leached soil was larger at lower irrigation frequency. The salinity of irrigation water under SDI with shallow emitter depth did not show any significant effect on increasing the soil salinity above tomato crop salt tolerance. Based on the results, it appears that the use of SDI with brackish irrigation water is an effective method for growing tomato crop in El-Salam Canal cultivated land especially with shallow emitter depth.     

Sugarcane water use from shallow water tables: implications for improving irrigation water use efficiency

The resource potential of shallow water tables for cropping systems has been investigated using the Australian sugar industry as a case study. Literature concerning shallow water table contributions to sugarcane crops has been summarised, and an assessment of required irrigation for water tables to depths of 2 m investigated using the SWIMv2.1 soil water balance model for three different soils. The study was undertaken because water availability is a major limitation for sugarcane and other crop production systems in Australia and knowledge on how best to incorporate upflow from water tables in irrigation scheduling is limited. Our results showed that for the three soils studied (representing a range of permeabilities as defined by near-saturated hydraulic conductivities), no irrigation would be required for static water tables within 1 m of the soil surface. Irrigation requirements when static water tables exceeded 1 m depth were dependent on the soil type and rooting characteristics (root depth and density). Our results also show that the near-saturated hydraulic conductivities are a better indicator of the ability of water tables below 1 m to supply sufficient upflow as opposed to soil textural classifications. We conclude that there is potential for reductions in irrigation and hence improvements in irrigation water use efficiency in areas where shallow water tables are a low salinity risk: either fresh, or the local hydrology results in net recharge.     

On-farm performance evaluation of improved traditional small-scale irrigation practices: A case study from Dire Dawa area, Ethiopia

Field evaluation of surface irrigation systems play a fundamental role to determine the efficiency of the system as it is being used and to identify management practices and system configurations that can be implemented to improve the irrigation efficiency. This study evaluated the performance of an ‘improved’ traditional small-scale irrigation practice at Adada, a representative small-scale irrigation practice in Dire Dawa Administrative Council, Eastern Ethiopia. In order to determine numerical values of performance measures, certain parameters were measured/observed before, during and after an irrigation event while farmers are performing their normal irrigation practice. These parameters include: irrigated crop, irrigation method, stream size, cutoff time, soil moisture deficiency, and field size, shape and spacing. The results showed that the irrigation water applied to a farmer's plot during an irrigation event/turn was generally higher than the required depth to be applied per event. Since the irrigation method used was end-dyked, the major cause of water loss was due to deep percolation. The deep percolation loss was 32% in sorghum, 57% in maize, and 70% in tomato and potato fields. The type of irrigation system used, the ridged irrigation practice and the poor irrigation scheduling in the study sites were the main problems identified in the management and operations of the schemes. The following corrective measures are recommended to improve the system: (1) farmers should regulate the depth of irrigation water they apply according to the type of crop and its growth stage, change the field irrigation system and/or configuration especially for shallow rooted row crops, to furrow system, (2) guidance and support to farmers in developing and introduction of appropriate irrigation scheduling, and (3) future development interventions towards improvement of traditional irrigation practices should also focus in improving the on farm irrigation systems in addition to improving physical infrastructure of the scheme.     

Drip Planner Chart: a simple irrigation scheduling tool for smallholder drip farmers

Drip irrigation is widely recognized as potentially one of the most efficient irrigation methods. However, this efficiency is often not achieved because systems are not always well designed or maintained and many farmers lack the tools to assess the crop water requirements and to monitor the soil moisture conditions in the field. There is a vast amount of literature on irrigation scheduling but little literature takes scientific information the next step by preparing practical guidelines for smallholder farmers. There is a large and widening gap between the state of the art irrigation scheduling tools and current on-farm irrigation practices. Most farmers find current irrigation scheduling tools overwhelming and lack the means and skills to install and operate them. It is suggested that farmers need simple, cheap and more comprehensive support tools to achieve improved irrigation management at the farm level. Wageningen University and Research Centre (WUR) developed the Drip Planner Chart (DPC) to provide smallholder farmers with a simple tool to schedule drip irrigation to the crops?? needs. DPC is a manual disk calculator to calculate daily irrigation requirement. Farmers?? feedback was the basis for developing the DPC. Using DPC over a three-year period in Spain resulted in a 14 % water saving and improved irrigation timing. Trials at smallholder farmer fields in Nepal and Zambia showed DPC advice is more adapted to the changing demands of the crop over the different growth stages and responds to the farmer??s quest for practical drip scheduling advice. This paper presents the Drip Planner Chart and the scientific validation of the accuracy of the DPC. Experiments on farmers?? fields show water saving in Nepal and improved yield in Zambia. In both countries an improved scheduling over the growing seasons was found using DPC.     

Assessing benefits of irrigation and nutrient management practices on a southeast Florida royal palm (Roystonea elata) field nursery

Many of the best management practices (BMPs) that are recommended for agricultural producers have not been scientifically evaluated for their conservation benefits considering the soil, climate, and hydrology of the proposed application location. The goal of this study was to compare royal palm (Roystonea elata) production in south Florida, USA, using tensiometer automated irrigation and reduced soil applications of nitrogen (N) and phosphorus (P), to that of traditional grower practices considering water savings, nutrient inputs, crop yield, crop nutrient status, soil nutrient status, and economic analyses. The study consisted of six treatments: (1) control (i.e., a grower irrigation rate and N and P fertilizer rates); (2) irrigation system automated to irrigate when soil water suction exceeded 5 kPa and the grower N and P rates; (3) irrigation system automated to irrigate when soil water suction exceeded 15 kPa and the grower N and P rates; (4) irrigation system automated to irrigate when soil water suction exceeded 15 kPa and 50% of the grower N and P rates; (5) the grower irrigation rate and 75% of the grower N and P rates; and (6) the grower irrigation rate and 50% of the grower N and P rates. Irrigation water volume applied, plant diameters, and plant heights were measured periodically throughout the study and plant tissue samples and soil samples were collected periodically for analysis of N and P content. Significant differences among treatments were only observed for the irrigation water volume applied. Automating the irrigation system to irrigate at soil suction exceeding 5 and 15 kPa resulted in 75 and 96% less water applied, respectively, than traditional irrigation scheduling practices used by a grower. Economic analyses suggested that all treatments would result in financial savings ranging from 7 to 34% per ha considering a 5-year, 2 ha investment. Thus, automating irrigation based on soil water suction for palm production in southern Florida, USA and similar locations will result in more sustainable agricultural production systems by benefiting the environment (less nutrients and water applied) and the grower (lower cost).     

基于SWAP模型的春玉米咸水非充分灌溉模拟

为了探究石羊河流域适宜春玉米生长的咸水非充分灌溉模式,应用SWAP模型模拟不同灌溉模式下的土壤水盐平衡、春玉米相对产量和相对水分利用效率,并预测了较长时期土壤水盐动态变化规律.研究结果表明:灌溉水矿化度为0.71 g/L和3.00 g/L的春玉米最优灌溉模式为生育期内灌4次水,灌溉定额均为408 mm,2种灌溉模式均能达到节约灌溉用水、提高作物产量和水分利用效率以及减少土体盐分累积量的目的.较长时期土壤水盐动态变化规律模拟结果表明:在冬灌条件下,春玉米最优灌溉模式下的土壤水分和盐分能够在模拟期内保持相对平稳的状态;在不同年份,相同土层土壤含水率随着土层深度的增加而增大,0.71 g/L的淡水灌溉土壤盐分主要累积在40~80 cm土层,3.00 g/L的微咸水灌溉土壤盐分主要累积在10~40 cm土层;5 a的模拟结果表明0.71 g/L和3.00 g/L的水持续灌溉5 a,不会引起土壤次生盐渍化.     

微咸水灌溉下土壤水盐动态及对作物产量的影响

华北平原农业灌溉用水非常紧缺,水资源日益缺乏与粮食需求日益增多之间的矛盾尖锐。充分利用微咸水资源是缓解这一矛盾的重要途径之一。该文以中国农业大学曲周试验站1997－2005年冬小麦和夏玉米微咸水灌溉田间长期定位试验为基础,研究了充分淡水、充分淡咸水、关键期淡水、关键期淡咸水和不灌溉等5个处理下土壤饱和电导率和含盐量的动态变化,探讨了微咸水灌溉对冬小麦和夏玉米产量的影响。结果表明：土壤水盐动态呈受灌溉和降雨影响的短期波动和受季节更替影响的长期波动;在正常降雨年份,使用微咸水进行灌溉是可行的,不会导致土壤的次生盐渍化;微咸水灌溉虽然导致冬小麦和夏玉米产量降低10%～15%,但节约淡水资源60%～75%。如果降雨量达到多年平均水平以及微咸水灌溉制度制订合理,微咸水用于冬小麦/玉米田间灌溉前景广阔。     

Assessing the groundwater dynamics and impacts of water saving in the Hetao Irrigation District, Yellow River basin

Water resources allocated to the agricultural sector in the Yellow River basin are being reduced due to severe water scarcity and increased demand by the non-agricultural sectors. In large-scale irrigation districts, the application of water-saving practices, e.g., improving the canal system, using water-saving irrigation technology and adjusting cropping patterns, is required for the sustainable agricultural development and the river basin environmental equilibrium. Adopting water-saving practices leads to lowering the groundwater table and to controlling salinity impacts related to excessive irrigation. However, assessing the effects of water-saving practices on the groundwater system requires further investigation. The Jiefangzha Irrigation Scheme of the Hetao Irrigation District is used as a case study for analyzing the temporal and spatial dynamics of the groundwater table. A lumped parameter groundwater balance model has been developed with this purpose and to assess impacts of various water-saving practices. The model was calibrated with monthly datasets relative to the non-frozen periods of 1997-1999 and validated with datasets from 2000 to 2002. Results indicate that canal seepage and deep percolation account for respectively 48% and 44% of the annual groundwater recharge. Groundwater discharge by direct evaporation and plant roots uptake represents 82% of the total annual groundwater discharge. After validation, the model was applied to assess the impacts of various canal and farm irrigation water-saving practices. It was observed that improvements in the canal system (e.g., canal lining, upgrading the hydraulic regulation and control structures, improving delivery schedules) might lower the groundwater table by 0.28-0.48 m, depending upon the level of implementation of these measures. Higher declines of the groundwater table are predicted when water-saving technologies are applied at both the canal and the farm systems. That decline of the water table favours salinity control and reduces capillary rise, thus reducing the groundwater evaporation and uptake by plant roots; that reduction may attain 128 mm. However, predictions may change depending on the way how water-saving measures are applied, which may be different of assumptions made; therefore, there is the need to perform a follow-up of the interventions in order to update predictions. Results indicate the need for appropriate research leading to improved irrigation management when the decline of the groundwater level will reduce groundwater contribution to vegetation growth.     

Optimal on-farm irrigation scheduling with a seasonal water limit using simulated annealing

As water resources are limited and the demand for agricultural products increases, it becomes increasingly important to use irrigation water optimally. At a farm scale, farmer's have a particularly strong incentive to optimize their irrigation water use when the volume of water available over a season is production limiting. In this situation, a farmer's goal is to maximize farm profit, by adjusting when and where irrigation water is used. However, making the very best decisions about when and where to irrigate is not easy, since these daily decisions require consideration of the entire remaining irrigation season. Future rainfall uncertainty further complicates decisions on when and which crops should be subjected to water stress. This paper presents an innovative on-farm irrigation scheduling decision support method called the Canterbury irrigation scheduler (CIS) that is suitable when seasonal water availability is limited. Previous optimal scheduling methods generally use stochastic dynamic programming, which requires over-simplistic plant models, limiting their practical usefulness. The CIS method improves on previous methods because it accommodates realistic plant models. Future farm profit (the objective function) is calculated using a time-series simulation model of the farm. Different irrigation management strategies are tested using the farm simulation model. The irrigation strategies are defined by a set of decision variables, and the decision variables are optimized using simulated annealing. The result of this optimization is an irrigation strategy that maximizes the expected future farm profit. This process is repeated several times during the irrigation season using the CIS method, and the optimal irrigation strategy is modified and improved using updated climate and soil moisture information. The ability of the CIS method to produce near optimal decisions was demonstrated by a comparison to previous stochastic dynamic programming schedulers. A second case study shows the CIS method can incorporate more realistic farm models than is possible when using stochastic dynamic programming. This case study used the FarmWi$e/APSIM model developed by CSIRO, Australia. Results show that when seasonal water limit is the primary constraint on water availability, the CIS could increase pasture yield revenue in Canterbury (New Zealand) in the order of 10%, compared with scheduling irrigation using current state of the art scheduling practice.     

Irrigation scheduling strategies for cotton to cope with water scarcity in the Fergana Valley, Central Asia

The Central Asian countries face high water scarcity due to aridity and desertification but excess water is often applied to the main irrigated crops. This over-irrigation contributes to aggravate water scarcity problems. Improved water saving irrigation is therefore required, mainly through appropriate irrigation scheduling. To provide for it, after being previously calibrated and validated for cotton in the Fergana region, the irrigation scheduling simulation model ISAREG was explored to simulate improved irrigation scheduling alternatives. Results show that using the present irrigation scheduling a large part of the applied water, averaging 20%, percolates out of the root zone. Several irrigation strategies were analyzed, including full irrigation and various levels of deficit irrigation. The analysis focused a three-year period when experiments for calibration and validation of the model were carried out, and a longer period of 33 years that provided for an analysis considering the probabilities of the demand for irrigation water. The first concerned a wet period while the second includes a variety of climatic demand conditions that provided for analyzing alternative schedules for average, high and very high climatic demand. Results have shown the importance of the groundwater contribution, mainly when deficit irrigation is applied. Analyzing several deficit irrigation strategies through the respective potential water saving, relative yield losses, water productivity and economic water productivity, it could be concluded that relative mild deficits may be adopted. Contrarily, the adoption of high water deficit that produce high water savings would lead to yield losses that may be economically not acceptable.     

不同灌溉制度对根层土壤盐分影响的模拟

以河套灌区沙壕渠灌域为例,采用SaltMod模型探讨了不同灌溉制度对作物根层土壤盐分的影响.利用2008-2010年基础资料对模型进行率定和验证并对研究区的根层土壤盐分进行模拟和预测.结果表明:在现有灌排条件下,沙壕渠灌域的盐渍化程度基本达到较为稳定的水平,且有轻微脱盐趋势,未来10 a后作物根层土壤盐分降低3%.生育期土壤水盐垂直交换运动强烈,对于控制土壤盐分而言,灌水量越小越好;作物根层土壤盐分随冬灌灌溉定额的增大而减小,不同冬灌灌溉定额对应的根层土壤盐分最初的增加量均较大,但增加的趋势随时间逐渐降低.根据当地作物种植结构,综合考虑节水灌溉、作物产量和根层土壤水盐环境,建议研究区较优的作物生育期综合净灌溉定额为2 700~3 500 m³/hm²,冬灌净灌溉定额为2 700 m³/hm².     

Modeling the effects of saline water use in wheat-cultivated lands using the UNSATCHEM model

Waters of poor quality are often used to irrigate crops in arid and semiarid regions, including the Fars Province of southwest Iran. The UNSATCHEM model was first calibrated and validated using field data that were collected to evaluate the use of saline water for the wheat crop. The calibrated and validated model was then employed to study different aspects of the salinization process and the impact of rainfall. The effects of irrigation water quality on the salinization process were evaluated using model simulations, in which irrigation waters of different salinity were used. The salinization process under different practices of conjunctive water use was also studied using simulations. Different practices were evaluated and ranked on the basis of temporal changes in root-zone salinity, which were compared with respect to the sensitivity of wheat to salinity. This ranking was then verified using published field studies evaluating wheat yield data for different practices of conjunctive water use. Next, the effects of the water application rate on the soil salt balance were studied using the UNSATCHEM simulations. The salt balance was affected by the quantity of applied irrigation water and precipitation/dissolution reactions. The results suggested that the less irrigation water is used, the more salts (calcite and gypsum) precipitate from the soil solution. Finally, the model was used to evaluate how the electrical conductivity of irrigation water affects the wheat production while taking into account annual rainfall and its distribution throughout the year. The maximum salinity of the irrigation water supply, which can be safely used in the long term (33 years) without impairing the wheat production, was determined to be 6 dS m^?1. Rainfall distribution also plays a major role in determining seasonal soil salinity of the root zone. Winter-concentrated rainfall is more effective in reducing salinity than a similar amount of rainfall distributed throughout autumn, winter, and spring seasons.     

论膜下滴灌技术在干旱-半干旱地区节水抑盐灌溉中的应用

以干旱 -半干旱的新疆地区为重点 ,分析了传统盐碱地开发改良的缺陷与不足 ,提出了干旱 -半干旱地区盐碱地开发与改良的新思路 -膜下滴灌技术。膜下滴灌集地膜覆盖与滴灌的优点于一体 ,对土壤的水、盐、热状况有良好的调节作用。膜下滴灌在西北地区已有应用 ,经生产实践证明有良好的节水、洗盐和生产效益。