Critical points: interactions between on-farm irrigation systems and water distribution network

In this work, a new model useful to analyze interactions between the on-farm irrigation system supplied by critical points and the water supply network management was developed. The model evaluates the impacts of changes in the pressure head and demand simultaneity (number of open hydrants at a given time) on the irrigation system and evaluates emitter discharge and uniformity. It also estimates the potential reductions in crop yield due to decreased emission uniformity. The methodology is applied in the Bembézar Irrigation District (Southern Spain). Results show that the additional cost required for providing maximum pressure to the critical field does not offset the increase in crop yield. Hence, an increment from 91.7 to 92.1 % in yield in the critical field would represent increases in energy consumption from 0.15 to 0.17 kWh m^?3 of water. Also, the unit energy cost could be reduced by up to 0.11 kWh m^?3 without implying significant reductions in crop yield. The importance of a good selection of emitters in the critical fields (fields that are supplied by the critical hydrants) was also evaluated.     

Farmers’ incentives to save water with new irrigation systems and water taxation—A case study of Serbian potato production

Drip irrigation systems and irrigation strategies like deficit irrigation (DI) and partial root drying (PRD) are potential water saving irrigation systems and strategies. This paper analyses the Serbian farmer's economic incentive to use these water saving systems and strategies instead of the present sprinkler irrigation. The analysis is a partial budgeting analysis, based on irrigation application efficiency from the literature, standard figures for power requirements, pumping efficiency and friction losses for various sources of water and pressure requirements, yields and water use from recent Serbian field experiments, as well as prices and cost structures for potatoes collected in the Belgrade region. The analysis shows that changing the present system and strategy can save a significant amount of water (almost 50%). At the same time, however, irrigation costs are also significantly increased (more than doubled), and the total production costs are increased by 10% (deficit drip irrigation) and 23% (PRD). Increased taxes on water, investment subsidies, increased energy prices, and an increased yield or yield quality may provide incentives for farmers to change to new systems and strategies. The analysis indicates that a 0.80 to 1.97 € m⁻³ water tax is needed to make deficit drip irrigation and PRD profitable. The socioeconomic cost of providing water for irrigation and the alternative value of saved water are probably not that high. Thus, water taxation may not be a socioeconomic efficient means to improve the irrigation water productivity of Serbian potato production. Drip irrigation and PRD may, however, also increase the yield quality, and a 10-23% quality premium (price increase) is needed to make deficit drip irrigation and PRD profitable.     

A comparison between the gross energy requirements of different irrigation systems in Israel

Summary The energy requirements for manufacturing irrigation equipment were evaluated from a survey of a number of factories and workshops in Israel.Based on the results obtained and the life span of the components, the annual amortization of energy by high-pressure (overhead sprinklers), medium-pressure (undertree sprinklers and sprayers) and low-pressure (drip lines) irrigation systems was calculated for citrus orchards and cotton crops as irrigated in Israel. For citrus orchards a low-pressure sprayer system amortized 1.5 GJ ha^–1 y^–1 more energy than a medium-pressure undertree sprinkler system, and 2.7 GJ ha^–1 y^–1 more than a high-pressure, overhead sprinkler system. For irrigating a cotton crop, the low-pressure drip system used 6.8 GJ ha^–1 y^–1 more embodied energy than the movable, high-pressure overhead sprinkler system.The annual energy invested in irrigation water conveyance through the National Water Carrier, at the current hydraulic pressure of 500 kPa at the farm gate, varies for a cotton crop from 20 to 45 GJ ha^–1 y^–1 in the northern region and from 70 to 215 GJ ha^–1 y^–1 in the southern region of Israel, when irrigated with 4,050 m³ ha^–1. For a citrus orchard this energy input varies from 60 to 75 GJ ha^–1 y^–1 in the central region and from 120 to 375 GJ ha^–1 y^–1 in the southern regions, when irrigated with 7,200 m³ ha^–1. For obtaining the same yield in the south as in the north, the energy input for water conveyance has to be increased by 12% in the case of a cotton crop and by 7% in the case of a citrus orchard. Thus, in the north the annual energy amortization of a dripline irrigation system amounts to one third of that expended on water conveyance but in the south amounts to one-eighteenth or less, indicating the large regional dependency of energy inputs for irrigation.Calculations show that the reduction in energy requirement for water conveyance needed by irrigation systems operating at lower pressures compensates for their higher energy losses in system amortization. For example, in citrus irrigation the substitution of medium-pressure undertree sprinkler systems for high-pressure overhead sprinkler systems was calculated to save 8% of the total energy expenditure for water conveyance to the farm gate. This would amount to a saving of 7 GJ ha^–1 y^–1 for citrus in the central region and of 8 GJ ha^–1 y^–1 in the south. For cotton the substitution of low pressure dripline systems for high-pressure overhead sprinkler systems could save 16% of the total energy expenditure for pressurized water conveyance. This would amount to a saving of 8 GJ ha^–1 y^–1 in the northern region increasing to 10 GJ ha^–1 y^–1 in the south, taking into account a higher irrigation water requirement.Contribution from the Agricultural Research Organization, Bet Dagan, Israel. No. 1589-E, 1985 series     

Management model for decision support when applying low quality water in irrigation

Use of low quality water for irrigation of food crops is an important option to secure crop productivity in dry regions, alleviate water scarcity and recycle nutrients, but it requires assessment of adverse effects on health and environment. In the EU-project “SAFIR¹” a model system was developed that combines irrigation management with risk evaluation, building on research findings from the different research groups in the SAFIR project. The system applies to field scale irrigation management and aims at assisting users in identifying safe modes of irrigation when applying low quality water. The cornerstone in the model system is the deterministic “Plant-Soil-Atmosphere” model DAISY, which simulates crop growth, water and nitrogen dynamics and if required heavy metals and pathogen fate in the soil. The irrigation and fertigation module calculates irrigation and fertigation requirements based on DAISY's water and nitrogen demands. A Water Source Administration module keeps track of water sources available and their water quality, as well as water treatments, storage, and criteria for selection between different sources. At harvest, the soil concentrations of heavy metals and pathogens are evaluated and the risk to consumers and farmers assessed. Crop profits are calculated, considering fixed and variable costs of input and output. The user can run multiple “what-if” scenarios that include access to different water sources (including wastewater), water treatments, irrigation methods and irrigation and fertilization strategies and evaluate model results in terms of crop yield, water use, fertilizer use, heavy metal accumulation, pathogen exposure and expected profit. The management model system can be used for analysis prior to investments or when preparing a strategy for the season.     

提高毛水生产率研究

分析了减损性节水和增效性节水与水分生产率的概念,论述了农业技术在优种、培肥土壤、精耕细作、覆膜与化肥及水利技术在适时适量灌溉、输水系统减损、灌水技术、雨养农业农田基本建设等方面对提高水分生产率的作用。重点指出当前亟须加大育种投入,使流失的有机肥归田,抓好城市肥源归田、灌区输水系统管道化、山区农田基本建设3类试点,要农业与水利相结合,发挥各自优势,提高水分生产率,提高单产。     

Evaluation of the influence of irrigation methods and water quality on sugar beet yield and water use efficiency

Rapid urbanization and industrialization have increased the pressure on limited existing fresh water to meet the growing needs for food production. Two immediate responses to this challenge are the efficient use of irrigation technology and the use of alternative sources of water. Drip irrigation methods may play an important role in efficient use of water but there is still limited information on their use on sugar beet crops in arid countries such as Iran. An experiment was conducted to evaluate the effects of irrigation method and water quality on sugar beet yield, percentage of sugar content and irrigation water use efficiency (IWUE). The irrigation methods investigated were subsurface drip, surface drip and furrow irrigation. The two waters used were treated municipal effluent (EC = 1.52 dS m⁻¹) and fresh water (EC = 0.509 dS m⁻¹). The experiments used a split plot design and were undertaken over two consecutive growing seasons in Southern Iran. Statistical testing indicated that the irrigation method and water quality had a significant effect (at the 1% level) on sugar beet root yield, sugar yield, and IWUE. The highest root yield (79.7 Mg ha⁻¹) was obtained using surface drip irrigation and effluent and the lowest root yield (41.4 Mg ha⁻¹) was obtained using furrow irrigation and fresh water. The highest IWUE in root yield production (9 kg m⁻³) was obtained using surface drip irrigation with effluent and the lowest value (3.8 kg m⁻³) was obtained using furrow irrigation with fresh water. The highest IWUE of 1.26 kg m⁻³ for sugar was obtained using surface drip irrigation. The corresponding efficiency using effluent was 1.14 kg m⁻³. Irrigation with effluent led to an increase in the net sugar yield due to an increase in the sugar beet root yield. However, there was a slight reduction in the percentage sugar content in the plants. This study also showed that soil water and root depth monitoring can be used in irrigation scheduling to avoid water stress. Such monitoring techniques can also save considerable volumes of irrigation water and can increase yield.     

新疆三工河流域灌区实行节水灌溉水费标准分析

利用工程实际资料，对井渠结合灌区的供水成本及水费标准进行分析讨论，提出现阶段水费计收标准以及加强灌区灌溉管理、降低供水成本、提高灌溉效益的初步建议，并为灌区作物结构优化设计提供依据。     

Water use in rice schemes in the Senegal river Delta and Valley

The water use of rice schemes was derived from field measurements made during the 1991 and 1992 season at 13 irrigation schemes situated in the delta and valley of the Senegal river. The seasonal water consumption, as well as the water distribution throughout the season and the operation of the pumping stations were evaluated. The water consumption was compared with standards which ranged from 16,650 to 21,100 m³ ha^–1 depending on the season and the location of the scheme. Half of the analyzed schemes used more water than required. Analysis of the water distribution throughout the season revealed that in general the supply follows the demand. In small-scale schemes however, the fit between supply and demand is often lacking, resulting in crop stress and yield reduction. Furthermore, the study shows that the capacity of half of the pumping stations are under-used as a result of a long stretched saturation period and/or the irrigation of only a small fraction of the total area of the scheme.     

Irrigation for crops in a sub-humid environment VII. Evaluation of irrigation strategies for cotton

Summary Empirical functions to predict the nitrogen uptake, increase in LAI and minimum leaf water potential (LWP) of cotton were incorporated into a water balance model for the Namoi Valley, N.S.W. A function was then developed to describe the lint yield of irrigated cotton as a function of water stress days at 4 stages of development, total nitrogen uptake and days of waterlogging. A water stress day was defined as predicted minimum leaf water potential less than -1.8 MPa up to 90 days after sowing and -2.4 MPa there-after; stress reduced yield by up to 40 kg lint ha^–1 d^–1 with greatest sensitivity at 81–140 days after sowing and when N uptake was highest. Nitrogen uptake was reduced by 0.98 kg per ha and yield reduced by 33.2 kg lint ha^–1 for each day of waterlogging. The model was used to evaluate various irrigation strategies by simulating production of cotton from historical rainfall data. With a water supply from off farm storage, net returns ($ M1^–1) were maximized by allocating 7 Ml ha^–1 of crop. The optimum practice was not to irrigate until 60 days from sowing and until the deficit in the root zone reached 50%. When the supply of water was less than 7 Ml ha^–1 there was no advantage in either delaying the start of irrigation or irrigating at a greater deficit; it was economically more rational to reduce the area shown or, if already sown, to irrigate part with 6 Ml ha^–1 and leave the rest as a raingrown crop. Irrigation decisions are compromises between reducing the risk of water stress and increasing the risk of waterlogging. The simulation showed that there is no single set of practices that is always best in every season; in a number of seasons practices other than those which on average are best, give better results.     

灌水处理对冬小麦生理生长特性等的影响研究

通过对冬小麦不同生育期进行有限灌溉的大田试验,研究不同水分处理对冬小麦的土壤水分变化、株高、叶面积指数、光合特性、产量以及水分利用效率的影响。结果表明:①灌水量越大,含水量变化的土层深度越大;并且土层深度越大,含水量的变化越小。②开花期灌水对缺水处理叶面积指数和株高的补偿效应明显。③各处理的光合特性日变化趋势一致,蒸腾速率和气孔导度日变化趋势均是双峰曲线,光合速率日变化趋势均是单峰曲线,均有"午休"现象。④开花水有利于籽粒的形成,只灌开花水也可获得较高产量。但产量与总灌水量之间呈抛物线关系。⑤单叶和产量水平的水分利用效率均随灌水量的不同而不同。总灌水量越大,叶片水分利用效率越大,灌溉水利用效率越低,水分利用效率越低。⑥综合考虑,全生育期只灌1次75 mm开花水的处理最合理。     

长距离大流量输水管涵贝类防除研

淡水贝类在河道、沟渠中的生长非常普遍，这些贝类通常在输水管线中生长、死亡，引起管道堵塞，水流不畅等诸多不良后果，由此对南方地区长距离大流量大断面输水管涵内生长的贝类种类及危害性等进行初步调查与研究，并提出初步的防除技术思路，对类似工程有一定的参考价值。     

石津灌区农业水资源利用效率的初步研究

采用灌溉水利用系数、灌溉效率和水分生产率3种指标,结合石津灌区2004~2005年冬小麦生育期内的耗水量和产量,从灌区管理与水资源利用的角度,评价了该灌区农业水资源的利用状况。同时运用地下水位观测资料分析计算了田间渗漏水量和垂向回归水量,定量分析了垂向回归水补给量对灌溉效率的影响。经计算,灌溉水利用系数为0.476、灌溉效率平均为0.667、灌溉水分生产率不同尺度分别为1.214、1.350、1.490、1.751 kg/m3。回归水的再利用使得灌溉效率值平均提高了18.8%。     

Response of cotton to different soil water deficits on clay soils

Summary Cotton was grown under sprinkler irrigation on a silty clay soil at Keiser, Arkansas, for the 1987, 1988 and 1989 growing seasons. Irrigation treatments consisted of maximum soil water deficits (SWD) of 25, 50 and 75 mm and a nonirrigated control. While the irrigated treatments were significantly different from the control for plant height and total seedcotton yield, significant differences among the three irrigated treatments were only observed for plant height. Yields were significantly lower in 1989 than in the other two years of the study, due in part to later planting. The 3-year averages for total seedcotton yield were 3280 and 2870 kg ha^–1 for irrigated and nonirrigated, respectively, for an average increase corresponding to irrigation of 416 kg ha^–1 or 14.5% of the nonirrigated yield. The maximum increase was observed in 1988 as 602 kg ha^–1 or 20.6% of the nonirrigated yield for that year. The 75 mm allowable SWD was the most efficient treatment and resulted in a 3-year average of 3.85 kg ha^–1 additional seedcotton (above the nonirrigated) harvested for each 1 mm of irrigation applied. Maintaining the SWD below a 75 mm maximum required an average of four irrigations and 110 mm of irrigation water per year.     

农业灌区改革中的水权管理探讨

针对目前多数灌区供水体制管理中存在的问题,围绕水权探讨改革措施。指出模糊水权是灌区用水的制约因素,概述灌区水权改革历程,分析水管理部门、灌区管理机构和用水户的关系,提出应保障灌区用水转让权、明晰水权与灌区资产权利关系,为灌区供水体制管理改革提供参考。     

调亏灌溉对日光温室青茄品质和耗水规律的影响

在日光温室滴灌条件下采用小区试验方法,研究了不同生育期不同程度调亏灌溉对青茄耗水规律、产量、品质和水分利用效率的影响。结果表明,温室青茄耗水高峰出现在成熟采摘期,该阶段耗水模系数在49.96%～64.11%之间;苗期的耗水量最小,其阶段耗水模系数在8.64%～16.68%之间。苗期和成熟采摘期适度调亏灌溉(灌水定额为适宜供水的80%)可提高青茄产量和水分利用效率,开花坐果期水分过度亏缺(灌水定额为适宜供水的60%)对青茄品质有所改善,但显著降低青茄产量和灌溉水利用效率。综合考虑产量和品质,拟定日光温室青茄滴灌条件下适宜的灌溉制度为,灌水周期10d,苗期和成熟采摘期适度亏水,灌水定额分别为12mm和20mm;开花坐果期宜充分灌溉,灌水定额为25mm。     

Response of Vitis vinifera cv. ‘Tempranillo’ to partial rootzone drying in the field: Water relations, growth, yield and fruit and wine quality

This paper reports the effects of irrigation amount and partial rootzone drying (PRD) on water relations, growth, yield and wine quality of Vitis vinifera cv. ‘Tempranillo’ during two consecutive years in a commercial vineyard with a deep, light-clay soil located in Requena, Valencia, Spain. Partial rootzone drying applied at two amounts (100% and 50% of the estimated crop evapotranspiration), was compared to conventional drip irrigation, and also to rainfed vines. Results showed that the effects of irrigation amount on yield and wine quality were different between years. In 2003 with low yield values (around 6.3 t ha⁻¹) irrigation did neither affect grape production nor wine quality. However, in the following year, with much higher general yield (17 t ha⁻¹), the high irrigation dose increased yield by 30% compared to rainfed vines and it also increased must total soluble solids and wine alcohol content. In both seasons, PRD did not significantly affect physiological parameters, nor growth, yield or fruit and wine quality, when compared to the same amount of water applied by conventional drip irrigation. Overall these results suggest that, under our experimental conditions, it was the irrigation amount rather than the system of application what affected vine performance, indicating the difficulties of successfully employing the PRD type of irrigation with a drip system in heavy and deep soils.     

海河流域冬小麦水分生产率特征分析

以海河流域为研究对象,以农田总供水水分生产率(WUEa)和灌溉水分生产率(WUEi)为评价指标,运用对流域内典型灌区的调查资料,计算了海河流域主要作物冬小麦的用水效率并进行特征分析,得到了其水分生产率的分布和变化规律。结果表明,WUEa在田间尺度上均值为1.50 kg/m3、灌区尺度上均值为0.97kg/m3,WUE在...     

Using drainage systems for supplementary irrigation

The use of drainage systems for supplementary irrigation is widespread in The Netherlands. One of the operating policies is to raise the surface water level during the growing season in order to reduce drainage (water conservation) or to create subsurface irrigation. This type of operation is based on practical experience, which can be far from optimal.To obtain better founded operational water management rules a total soil water/surface water model was built. In a case study the effects of using the drainage system in a dual-purpose manner on the arable crop production were simulated with the model. Also, the operational rules for managing this type of dual-purpose drainage systems were derived.The average annual simulated increase in crop transpiration due to water conservation and water supply for subsurface irrigation are 6.0 and 5.4 mm.y^–1, respectively. This is equivalent with 520 × 10³ and 460 × 10³ Dfl.y^–1 for the pilot region (2 Dfl 1 US $). The corresponding investments and operational costs are 600 × 10³ Dfl and 9 × 10³ Dfl.y^–1 for water conservation and 3200 × 10³ Dfl and 128 × 10³ Dfl.y^–1 for subsurface irrigation. Hence, water conservation is economically very profitable, whereas subsurface irrigation is less attractive.Comparing the management according to the model with current practice in a water-board during 1983 and 1986 learned that benefits can increase with some 50 and 500 Dfl per ha per year, respectively.     

灌排方案对避雨番茄需水特性与产量的影响

为了实现南方地区番茄节水、优质、高效生产,在避雨栽培条件下,研究了不同灌排方式对番茄需水特性与产量的影响.研究结果表明:各亏缺灌溉处理土壤含水率随时间总体呈下降趋势,暗管埋深08 m的处理较埋深06 m处理,土壤含水量下降更快但不明显.番茄不同生育阶段的蒸发蒸腾量差别较大,表现为始花坐果期>果实成熟与采收期>苗期.随着番茄的生长,其日蒸发蒸腾量大体呈逐渐上升的趋势.在不同灌排模式和避雨措施条件下,苗期的日蒸发蒸腾量变化范围为107～271 mm／d,始花坐果期日蒸发蒸腾量变化范围为160～309 mm／d,果实成熟与采收期日蒸发蒸腾量变化范围为178～335 mm／d.在相同的排水措施,不同灌溉条件下,番茄果实产量随着灌水量的减少而减少,水分利用率和灌溉水利用率却随着灌水量的减少而增大.研究可为南方避雨栽培下番茄灌排方式的选择及其节水、优质、高产提供参考.     

Irrigation for crops in a sub-humid environment

Summary A four year study examined the effect of irrigating at various water deficits at different times in the growing season, in combination with a range of nitrogen fertilizer rates, on the growth, yield and quality of cotton. The major effect of irrigation treatment on growth was to increase leaf area and plant size; net assimilation rate in the vegetative phase was not affected by irrigation treatment. The initial rate of boll setting was slightly faster in low nitrogen and less frequent irrigation treatments, but by day 180 (immediately prior to defoliation), all treatments had 60% of total dry weight as bolls and 7% as leaf. The best irrigation strategy varied from year to year due to the variable rainfall pattern. Irrigation when 80% of the available soil moisture had been depleted in the first half of the season only decreased total lint yield by up to 12% in two of the four seasons. During the second half of the season the 80% level of depletion decreased yield by an average of 15% but gave an earlier crop. Yield was reduced by up to 17% if irrigation at 40–60% of available moisture depletion in the first half of the season was followed by irrigation at 80% of available moisture depletion in the second half of the season. A rainfed treatment yielded from 16 to 43% less than the heaviest yielding irrigation treatment. After irrigation there was evidence of poor aeration in the soil which was most severe and lasted the longest at 30 cm depth. Heaviest yields were obtained with 100–150 kgN ha^–1, except in rainfed treatments where 0–50 kgN ha^–1 was sufficient. Irrigation at only 40% of available moisture depletion decreased nitrogen uptake in all seasons. Treatment effects on fibre quality in these experiments were small and variable. Nitrogen fertilizer generally increased length and strength but decreased micronaire. Stress during boll filling decreased micronaire and length in two of the four seasons.