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1.
In arid and semi-arid regions, effluent from sub-surface drainage systems is often saline and during the dry season its disposal poses an environmental problem. A field experiment was conducted from 1989 to 1992 using saline drainage water (EC=10.5–15.0 dS/m) together with fresh canal water (EC=0.4 dS/m) for irrigation during the dry winter season. The aim was to find if crop production would still be feasible and soil salinity would not be increased unacceptably by this practice. The experimental crops were a winter crop, wheat, and pearl-millet and sorghum, the rainy season crops, grown on a sandy loam soil. All crops were given a pre-plant irrigation with fresh canal water. Subsequently, the wheat crop was irrigated four times with different sequences of saline drainage water and canal water. The rainy season crops received no further irrigation as they were rainfed. Taking the wheat yield obtained with fresh canal water as the potential value (100%), the mean relative yield of wheat irrigated with only saline drainage water was 74%. Substitution of canal water at first post-plant irrigation and applying thereafter only saline drainage water, increased the yield to 84%. Cyclic irrigations with canal and drainage water in different treatments resulted in yields of 88% to 94% of the potential. Pearl-millet and sorghum yields decreased significantly where 3 or 4 post-plant irrigations were applied with saline drainage water to previous wheat crop, but cyclic irrigations did not cause yield reduction. The high salinity and sodicity of the drainage water increased the soil salinity and sodicity in the soil profile during the winter season, but these hazards were eliminated by the sub-surface drainage system during the ensuing monsoon periods. The results obtained provide a promising option for the use of poor quality drainage water in conjunction with fresh canal water without undue yield reduction and soil degradation. This will save the scarce canal water, reduce the drainage water disposal needs and associated environmental problems.  相似文献   

2.
Summary Lucerne was irrigated for three years on a slowly permeable, duplex soil, with saline water up to 2.4 dS m–1 without significant yield decline. Irrigation water of 4.5 dS m–1 significantly reduced yield. Lucerne yield was most closely related to the soil ECe of the 0–15 cm depth, rather than the total rootzone, and was described by; Relative yield=100–6.5 (ECe-2.1). While lucerne roots reached depths of at least 150 cm, approximately 80% of total root length was located in the 0–60 cm depth.Increasing salinity increased the plant concentrations of sodium and chloride, however, these changes were not closely related to changes in yield.Soil salinity increased with increasing salinity of the applied water. However, during the irrigation season water penetration and the accumulation of salt within the profile was predominantly restricted to the 0–60 cm depth. No portion of the applied irrigation water was available as a leaching fraction. Any leaching of salts to the watertable, particularly below 120 cm, was due to winter rainfall rather than the application of summer irrigation water.Ripping the soil to a depth of 75 cm increased water infiltration and resulted in increased crop yields, but did not significantly affect the crop relative yield-soil ECe relationship.From the results it is proposed that on the slowly permeable duplex soils, when watertable depth is controlled, management strategies for lucerne irrigated with saline water should be based on controlling the salinity of the shallow soil depths, to 60 cm.  相似文献   

3.
A relationship between crop yield and irrigation water salinity is developed. The relationship can be used as a production function to quantify the economic ramifications of practices which increase irrigation water salinity, such as disposal of surface and sub-surface saline drainage waters into the irrigation water supply system. Guidelines for the acceptable level of irrigation water salinity in a region can then be established. The model can also be used to determine crop suitability for an irrigation region, if irrigation water salinity is high. Where experimental work is required to determine crop yield response to irrigation water salinity, the model can be used as a first estimate of the response function. The most appropriate experimental treatments can then be allocated. The model adequately predicted crop response to water salinity, when compared with experimental data.Abbreviations A Crop threshold rootzone salinity in Equation of Maas and Hoffman (dS/m) - B Fractional yield reduction per unit rootzone salinity increase (dS/m)–1 - Ci Average salinity of applied water (dS/m) - Cr Average salinity of rainfall (dS/m) - Cs Linearly averaged soil solution salinity in the rootzone (dS/m) - Cse Linearly averaged soil saturation extract salinity in the rootzone (dS/m) - Cw Average salinity of irrigation supply water (dS/m) - Cz Soil solution salinity at the base of the crop rootzone (dS/m) - C Mean root water uptake weighted soil salinity in equation of Bernstein and François (1973) (dS/m) - Ep Depth of class A pan evaporation during the growing season (m) - ETa Actual crop evapotranspiration during the growing season (m) - ETm Maximum crop evapotranspiration during the growing season (m) - I The total depth of water applied during the growing season (including irrigation water and rainfall) (m) - K Empirical coefficient in leaching equation of Rhoades (1974) - Kc Crop coefficient for equation of Doorenbos and Pruit (1977) to estimate crop water use - Ky Yield response factor in equation of Doorenbos and Kassam (1974) - LF The leaching fraction - Ro Depth of rainfall runoff during the growing season (m) - R Depth of rainfall during the growing season (m) - W Depth of irrigation water applied during the growing season (m) - Y Relative crop yield - Ya Actual crop yield (kg) - Ym Maximum crop yield (kg) - /z Dimensionless depth for equation of Raats (1974), and empirical coefficient for the leaching equation of Hoffman and van Genutchen (1983)  相似文献   

4.
Artificial subsurface drainage is not an option for addressing the saline, shallow ground water conditions along the west side of the San Joaquin Valley because of the lack of drainage water disposal facilities. Thus, the salinity/drainage problem of the valley must be addressed through improved irrigation practices. One option is to use drip irrigation in the salt affected soil.A study evaluated the response of processing tomato and cotton to drip irrigation under shallow, saline ground water at depths less than 1 m. A randomized block experiment with four irrigation treatments of different water applications was used for both crops. Measurements included crop yield and quality, soil salinity, soil water content, soil water potential, and canopy coverage. Results showed drip irrigation of processing tomato to be highly profitable under these conditions due to the yield obtained for the highest water application. Water applications for drip-irrigated tomato should be about equal to seasonal crop evapotranspiration because yield decreased as applied water decreased. No yield response of cotton to applied water occurred indicating that as applied water decreased, cotton uptake of the shallow ground water increased. While a water balance showed no field-wide leaching, salinity data clearly showed salt leaching around the drip lines.  相似文献   

5.
Maximization of crop yields when the salinity of irrigation water is high depends on providing plant transpiration needs and evaporative losses, as well as on maintaining minimum soil solution salinity through leaching. The effect of the amount of applied irrigation water was studied regarding transpiration, yields, and leaching fractions as a function of irrigation water salinity. Bell pepper (Capsicum annum L. vars. Celica and 7187) in protected growing environments in the Arava Valley of Israel was used as a case study crop to analyze water quantity–salinity interactions in a series of lysimeter, field and model simulation experiments. Leaching fraction was found to be highly influenced by plant feedback, as transpiration depended on root zone salinity. Increased application of saline irrigation water led to increased transpiration and yields. The higher the salinity level, the greater the relative benefit from increased leaching. The extent of leaching needed to maximize yields when irrigating with saline water may make such practice highly unsustainable.  相似文献   

6.
不同土壤基质势对滴灌枸杞生长的影响研究   总被引：1，自引：0，他引：1  
采用滴头正下方0．2m深处埋设负压计控制土壤基质势下限进行水盐调控,通过田间试验研究了不同土壤基质势对宁夏枸杞生长和产量的影响。试验结果表明,2010年枸杞生长周期内,随着土壤基质势的降低,不同处理的累计灌水量显著减少,不同土壤基质势处理对枸杞生长和产量都没有显著影响。当滴头正下方0．2m处土壤基质势为-20kPa时,...  相似文献   

7.
Unlike annual crops where reclamation leaching of salts can be readily conducted between cropping, leaching of salts in permanent crops that are drip irrigated pose challenges. A need exists to formulate and test a management-type of salinity model for drip irrigation of table grapes. The model reported herein predicts the distribution of salts along the vine row and between the rows during the growing season, as affected by reactivity of salts of the applied irrigation water as well as rate and duration of drip application. The calibrated model reproduced the initial field salinity profiles after repeated irrigation cycles by adjusting only the routing factor α which is the ratio of horizontal to vertical water flow. After eight cycles the profiles stabilized and the calibrated horizontal to vertical flow routing ratio was 0.6. There is remarkable agreement between measured and simulated salinity. Corresponding soil moisture profiles show the expected high water content with depth at the emitter, the decrease in surface water content with radial distance and the increase with depth, at the distal end of the wedge. Although the model is location specific it can be applied knowing soil, initial and boundary conditions, as well as irrigation application quantity and quality and as such can be applied location by location in order to assess flow and quality of deep percolation recharging the groundwater system. With this capacity the model can predict soil water quantity and quality outcomes for possible land and water management scenarios.  相似文献   

8.
河套灌区节水灌溉对土壤盐分累积规律的模拟研究   总被引：1，自引：0，他引：1  
在内蒙古河套实施农业节水对引黄灌区水资源可持续利用具有非常重要的意义。通过河套灌区土壤水盐动态的原位监测,并应用水盐运移和作物耦合模型HYDRUS-EPIC对不同灌溉条件下葵花土壤盐分累积规律进行分析。研究结果表明:现状滴灌条件下葵花生育期土壤表层(0~10cm)盐分呈累积趋势,全盐含量分别比传统地面灌溉和等量地面灌高115%和37%;葵花生育期0~100cm增加的全盐量(ΔC)滴灌比传统地面灌溉高305%,比等量地面灌溉低23%,淋洗是灌区滴灌不可或缺的抑盐措施;滴灌条件下葵花的产量比传统地面灌小6.5%;滴灌产量比等量地面灌高11.7%,增产效果明显。  相似文献   

9.
In the irrigated western U.S. disposal of drainage water has become a significant economic and environmental liability. Development of irrigation water management practices that reduce drainage water volumes is essential. One strategy combines restricted drainage outflow (by plugging the drains) with deficit irrigation to maximize shallow groundwater consumption by crops, thus reducing drainage that needs disposal. This approach is not without potential pitfalls; upward movement of groundwater in response to crop water uptake may increase salt and sodium concentrations in the root zone. The purposes for this study were: to observe changes in the spatial and temporal distributions of SAR (sodium adsorption ratio) and salt in a field managed to minimize drainage discharge; to determine if in situ drainage reduction strategy affects SAR distribution in the soil profile; and to identify soil or management factors that can help explain field wide variability. We measured SAR, soil salinity (EC1:1) and soil texture over 3 years in a 60-ha irrigated field on the west side of the San Joaquin Valley, California. At the time we started our measurements, the field was beginning to be managed according to a shallow groundwater/drainage reduction strategy. Soil salinity and SAR were found to be highly correlated in the field. The observed spatial and temporal variability in SAR was largely a product of soil textural variations within the field and their associated variations in apparent leaching fraction. During the 3-year study period, the percentage of the field in which the lower profile (90-180 cm) depth averaged SAR was above 10, increased from 20 to 40%. Since salinity was increasing concomitantly with SAR, and because the soil contained gypsum, sodium hazard was not expected to become a limiting factor for long term shallow groundwater management by drain control. It is anticipated that the technology will be viable for future seasons.  相似文献   

10.
实用型滴灌灌溉计划制定方法   总被引：19，自引：0，他引：19  
康跃虎 《节水灌溉》2004,(3):11-12,15
介绍了适合日光温室、塑料大棚等设施栽培和小块农田经济作物栽培滴灌灌溉计划制定的2种方法。方法一：将真空表负压计埋在滴头正下方20cm深度处监测土壤水势，每次的灌水量相同，或者将作物整个生育期分为2～3个生长阶段，每个生长阶段内每次的灌水量相同．只要土壤水势超出预定的范围，就进行灌溉。对于大部分作物，只要每次的灌水量在5mm左右，土壤水势保持在25～35kPa的范围内，就能获得比较理想的产量。方法二：在冠层顶部放置一个20cm标准蒸发皿，灌溉频率一定．将一个灌水周期内蒸发皿的蒸发量乘以比例系数作为下一个灌水周期的灌水量。对于大部分日光温室和塑料大棚栽培的作物来说，只要将这个比例系数定为1，灌水周期定为每天1次、每2天1次或每3天1次，就能获得比较理想的产量。  相似文献   

11.
Summary Irrigation is essential for economic production of some crops in semiarid climates. Benefits from irrigation may be partially offset by detrimental effects of rising water tables and salinization. Drainage systems are usually installed when the water table rises to the root zone, but installation of a drainage system and safe disposal of drainage water are expensive. The long-term consequences of a high saline water table on crop production, particularly as related to irrigation scheduling, has not been firmly established. A multiseasonal transient state model, known as the modified van Genuchten-Hanks model, was used to simulate cotton (Gossypium hirsutum L.) production using a three or four in-season irrigation schedule (3irr or 4irr) under both free drainage and water table conditions. Under drainage conditions, irrigation scheduling to avoid applying more water than the soil water-holding capacity during any irrigation event is important, whereas this factor is less important under water table conditions. Excess water during an irrigation causes a rise in the water table, but this water remains available for later crop use which lowers the water table. In the presence of a water table the simulations indicate, (1) higher yields are achieved by applying less irrigation during the crop season and more during the preirrigation for salt leaching purposes, (2) annual applied water must equal evapotranspiration to avoid long-term water table rise or depletion, and (3) high cotton yields can be achieved for several years even if the water table is saline and no drainage occurs if the irrigation water is low in salinity.  相似文献   

12.
新疆滴灌技术已在小麦作物上推广应用,但滴灌小麦农田大多受盐碱危害,为研究滴灌小麦水盐分布特点,通过测坑试验,分析了小麦各生育期土壤剖面上的水盐分布,结果表明,小麦滴灌条件下土壤水盐分布垂直方向受影响深度主要在0～60cm土层,在0～20cm土层水盐变化最为剧烈。土壤盐分分布变化范围和水分变化范围基本吻合。在0～100cm土壤剖面内,土壤含水量的分布呈随土层深度呈先降低后升高的趋势,而土壤盐分则基本上呈现先增加后减少再增加的分布特点。  相似文献   

13.
The influences of water quantity and quality on young lemon trees (Eureka) were studied at the University of Jordan Research Station at the Jordan Valley for 5 years (1996–2000). Five water levels and three water qualities were imposed via trickle irrigation system on clay loam soil. The primary effect of excess salinity is that it renders less water available to plants although some is still present in the root zone. Lemon trees water requirements should be modified year by year since planting according to the percentage shaded area, and this will lead into substantial water saving. Both evaporation from class A pan and the percentage shaded area can be used to give a satisfactory estimate of the lemon trees water requirement at the different growth stages. The highest lemon fruit yield was at irrigation water depth equal to evaporation depth from class A pan when corrected for tree canopy percentage area. Increasing irrigation water salinity 3.7 times increased average crop root zone salinity by about 3.8–4.1 times.The high salt concentration at the soil surface is due to high evaporation rate from wetted areas and the nature of soil water distribution associated with drip irrigation system. Then, the salt concentration decreased until the second depth, thereafter, salt concentration followed the bulb shape of the wetted soil volume under trickle irrigation. Irrigation water salinity is very important factor that should be managed with limited (deficit) irrigation. But increasing amount of applied saline water could result in a negative effect on crop yield and environment such as increasing average crop root zone salinity, nutrient leaching, water logging, increasing the drainage water load of salinity which might pollute ground water and other water sources.  相似文献   

14.
Summary Many irrigated lands in semi-arid regions of the world are underlain with saline high water tables. Water management is critical to maintain crop productivity under these conditions. A multi-seasonal, transient state model was used to simulate cotton and alfalfa production under various irrigation management regimes. The variables included in-season water application of 1.0 or 0.6 potential evapotranspiration (PET), and 18 or 33 cm pre-irrigation amounts for cotton. The water table was initially at a 1.5m depth and a 9 dS/m salinity. A impermeable lower boundary at 2.5 m depth was imposed. Irrigation water salinity was 0.4 dS/m. Climatic conditions typical to the San Joaquin Valley of California were used for PET and precipitation values. The simulations were for no-lateral flow and also lateral flow whereby the water table was raised to its initial level prior to each irrigation event. Uniform application of 1.0 PET provided for relative cotton lint yields and alfalfa yields of 95% or more for at least 4 years. In-season irrigation of cotton with 0.6 PET had higher yields when associated with a 33 cm rather than an 18 cm pre-irrigation. Lateral flow provided for higher cotton lint yields production than the no-lateral flow case for each pre-irrigation treatment. The beneficial effects of lateral flow diminished with time because of the additional salt which accumulated and became detrimental to crop production. Substantial alfalfa yield reductions occurred after the first year when irrigation was set at 0.6 PET regardless of other conditions. Evaporation losses from the soil during the cotton fallow season were higher when the soil water content entering the fallow season were higher.Research was supported by the University of California Salinity/ Drainage Task Force  相似文献   

15.
Summary Field studies were conducted for a period of ten years (1974 to 1984) on Typic Ustochrept to determine the sustained effects of saline irrigation water electrical conductivity (EC iw ) 3.2 dS/m, sodium adsorption ratio (SAR) 21 (mmol/1)1/2 and residual sodium carbonate (RSC) 4me/1, on the build up of salinity in the soil profile and yield of crops grown under fixed rice-wheat and maize/millet-wheat rotations. Saline waters were continuously used with and without the addition of gypsum (at the rate needed to reduce RSC to zero) applied at each irrigation. In maize/millet-wheat rotation, two additional treatments viz. (i) irrigation with 50% extra water over and above the normal 6 cm irrigation, and (ii) irrigation with good water and saline water alternately, were also kept. The results showed that salinity increased rapidly in the profile during the initial years but after five years (1979–1984) the average soluble salt concentration in 0–90 cm soil profile did not appreciably vary and the mean EC e values under saline water treatment remained almost similar to EC iw , under both the crop rotations.Saline water irrigation increased pH and Na saturation of the soil, reduced water infiltration rate and decreased yields of maize, rice and wheat. The differences in the build up of salinity and ESP of the soil under the two cropping sequences seemed to be related with the differences in leaching that occurred under rice-wheat and maize/millet-wheat rotations. Application of gypsum increased the removal of Na from the profile, appreciably decreased the pH and Na saturation and improved water infiltration rate and raised crop yields. Application of non-saline and saline waters alternately was found to be a useful practice but irrigation with 50% extra water to meet the leaching requirement did not control salinity and hence lowered crop yields.  相似文献   

16.
内蒙古河套灌区不同灌溉模式对土壤温度及盐分的影响   总被引：2，自引：0，他引：2  
针对内蒙古河套灌区井渠结合膜下滴灌这一灌排发展趋势,分别选取了黄灌(H)、井灌(J)、滴灌(D)3种灌溉模式,研究了土壤温度时空变化规律和生育期盐分平衡状况。结果表明:玉米生育期内不同灌溉模式膜内膜外土壤温度月季下降明显,且膜内外土壤温度差异随着时间的推移越来越小;玉米需水旺季(6、7月)膜内5cm土壤日温度受灌水影响程度依次是滴灌井灌黄灌,平均温度黄灌较井灌高0.47℃,较滴灌高1.18℃;自6月下旬开始膜内5cm 10日平均土壤温度黄灌始终高于井灌0.35~1.53℃,滴灌基本小于井灌;30日平均温度黄灌较井灌温度始终高0.34~1.02℃,较滴灌高1.12~1.98℃。生育期黄灌、井灌、滴灌0~100、0~60cm土壤均积盐,膜外积盐率0~60cm远大于0~100cm。若地面灌溉一年一洗盐,滴灌0~100cm盐分累积至井灌土壤盐分水平需2年一次秋浇洗盐。  相似文献   

17.
In both arid and semi-arid areas the use of saline water for irrigation is a common practice, even though it may cause a drop in crop yield and progressive soil salinization. In order to determine the most suitable irrigation strategy for higher yield, profitability, and soil salinity management of certain crops, the MOPECO-Salt Model has been developed. This model was first validated in the Eastern Mancha Agricultural System in Albacete (Spain) through a test carried out on onion crop in April-September 2009, where the simulated yield was 2% lower than the observed one. The model was then tested at Tal Amara Research Station in the Central Bekaa Valley Agricultural System (Lebanon) using data from a 5-year experiment on the effects of deficit irrigation on two cultivars of potato (Spunta: July-October 2001, and June-September 2002; and Agria: March-August 2004, 2005, and 2007). Furthermore, these results were compared with those obtained through AquaCrop, which does not currently assess crop response to salinity. Differences between observed and simulated yields were lower than 3% for MOPECO-Salt and up to 12% for AquaCrop. According to findings from simulations, the irrigation strategies without leaching fraction employed in both areas are remediable since the off-season rainfall is sufficient to wash out soluble salts supplied with irrigation water. Results showed that as much as 14.4% water could be saved when this strategy was adopted for onion crops.  相似文献   

18.
A field experiment was conducted for 10 years in the Nile Delta of Egypt to quantify the benefit of subsurface drainage on crop yield. During three crop rotations, subsurface drains at a spacing of 20 m and a depth of 1.5 m doubled the yield of cotton and rice and increased the yield of wheat and clover by 50%. No significant enhancement in crop yield was found from placing various envelope materials around the drains compared to no envelope. Drains of 75 mm diameter resulted in significantly lower yields (20% less) for cotton and rice than drains of 100 mm diameter but there were no yield differences for wheat and clover. Applying 10 Mg/ha of gypsum and deep plowing (25 cm deep) improved yields from 5 to 19% for all crops, cotton and clover having the largest yield improvement. Soil salinity to a depth of 1.5 m was reduced from an average 5.3–2.2 dS/m after 1 year of drainage without additional water being applied beyond the normal irrigation amounts and rainfall.  相似文献   

19.
滴灌条件下排水暗管间距对土壤盐分淋洗的影响   总被引：7，自引：0，他引：7  
在滴灌淋洗条件下设计暗管排水试验,研究暗管不同埋设间距(15、20、25 m)对土壤剖面盐分分布及脱盐淋洗效果的影响。结果表明:滴灌淋洗期间,0~70 cm土层含盐量显著降低,与CK相比,试验地不同地段土壤平均含盐量减少10 g/kg以上。从暗管上方至相邻暗管中点位置处不同剖面土壤平均脱盐率逐渐减小,15、20、25 m间距小区在0~100 cm埋深土壤中点位置处最大脱盐率分别为84.01%、77.75%、73.98%,土壤整体脱盐率介于51.82%~60.43%之间。吸水管埋管间距越小,小区暗管排水阶段排水流量越大,排水矿化度、电导率也越大,但成本会略高。15 m间距相比20、25 m间距小区每公顷多投入的成本和平均脱盐率差值分别为8 430、12 570元和4.78%、8.61%;15 m间距暗管处理在水平距离暗管0、5、7.5 m处土壤脱盐率最大值分别为86.47%、85.15%、84.01%,且排水期间排水流量、矿化度、电导率最大,分别为2 m~3/h、189.15 g/L和35.9 mS/cm;土壤盐分淋洗效果优于20、25 m间距小区,淋洗相同盐分含量土壤所需灌水量也低于20、25 m间距;2次灌水后0~70 cm土层盐分整体已降至10 g/kg以下,作物生长条件大为改善,适宜作为指导新疆盐渍土改良滴管条件下暗管间距布设参数的依据。  相似文献   

20.
Numerical evaluation of subsurface trickle irrigation with brackish water   总被引：1，自引：0，他引：1  
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.  相似文献   

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