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1.
The division of irrigation water in The Fayoum, Egypt, has been measured. Factors influencing this division are discussed: the hydraulic conditions at structures and canals, the operation regime of gates, lack of reliable gauge data for system operation, shortage of labour, and the water level in Lake Qarun. A deviation from uniform supply has been found for the entire Fayoum, but also along a lateral and sub-lateral. The reasons for this are discussed and suggestions for possible technical improvements of The Fayoum system are given.Abbreviations FWSBM Fayoum Water and Salt Balance Model Project - MSL Mean Sea Level at Alexandria - FID Fayoum Irrigation Department - mcm million cubic metres  相似文献   

2.
The irrigation system in The Fayoum is designed for a continuous supply of water (24 h a day, 7 days a week) to rotational units, which vary in size from about 20 to 500 fe. The Fayoum Irrigation Department is responsible for the delivery of irrigation water to the rotational units. Within the units, the farmers rotate the water in a seven days rotation.One of the characteristics of present water management of The Fayoum is the non-uniformity of the division of flow over the main canals. The purpose of this paper is: (i) to study the effects of this non-uniformity by comparing water management in tertiary units in an area with a (more than) sufficient water supply to an area subject to some water shortage; (ii) to discuss implications of the present tertiary unit water management for the water management of the entire The Fayoum.The findings are that: (i) the non-uniformity of the main system water supply has a strong effect on the water management in the tertiary units. Water shortage results in a lower cropping intensity and fallow land, no possibility to cultivate rice, and a possible trend towards salinization in the Seila area; (ii) the farmers in both research areas modify the official rotation schedule. These modifications create a high flexibility in the rotational units: The water supply for different crops and plots is adjusted almost to the minute.Glossary and abbreviations Bahar Gate-Tender - FaWMDI Fayoum Water Management and Drainage Improvement Project - fe Feddan (1 fe = 0.42 ha) - FID Fayoum Irrigation Department - Ganabiah Secondary or Sub-Secondary - IIP Irrigation Improvement Project - Kafr Satellite Village of a Larger Village with a Mayor - Mesqah Tertiary Canal - MSL Mean Sea Level at Alexandria - Nasbah Cluster of Fayoum Standard Weirs - Sheikh el Balad The Oldest of the Kafr (Elected Position)  相似文献   

3.
A great challenge for the agricultural sector is to produce more food from less water, particularly in arid and semi-arid regions which suffer from water scarcity. A study was conducted to evaluate the effect of three irrigation methods, using effluent versus fresh water, on water savings, yields and irrigation water use efficiency (IWUE). The irrigation scheduling was based on soil moisture and rooting depth monitoring. The experimental design was a split plot with three main treatments, namely subsurface drip (SSD), surface drip (SD) and furrow irrigation (FI) and two sub-treatments effluent and fresh water, which were applied with three replications. The experiment was conducted at the Marvdasht city (Southern Iran) wastewater treatment plant during 2005 and 2006. The experimental results indicated that the average water applied in the irrigation treatments with monitoring was much less than that using the conventional irrigation method (using furrows but based on a constant irrigation interval, without moisture monitoring). The maximum water saving was obtained using SSD with 5907 m3 ha−1 water applied, and the minimum water saving was obtained using FI with 6822 m3 ha−1. The predicted irrigation water requirements using the Penman-Monteith equation (considering 85% irrigation efficiency for the FI method) was 10,743 m3 ha−1. The pressure irrigation systems (SSD and SD) led to a greater yield compared to the surface method (FI). The highest yield (12.11 × 103 kg ha−1) was obtained with SSD and the lowest was obtained with the FI method (9.75 × 103 kg ha−1). The irrigation methods indicated a highly significant difference in irrigation water use efficiency. The maximum IWUE was obtained with the SSD (2.12 kg m−3) and the minimum was obtained with the FI method (1.43 kg m−3). Irrigation with effluent led to a greater IWUE compared to fresh water, but the difference was not statistically significant.  相似文献   

4.
A cost–benefit analysis was performed for a mature, commercial almond plantation [Prunus dulcis (Mill.) D.A. Webb] cv. Cartagenera in Southeastern Spain to determine the profitability of several regulated-deficit irrigation (RDI) strategies under subsurface drip irrigation conditions (SDI), compared to an irrigation regime covering 100% crop evapotranspiration (ETc). The plantation was subjected to three drip irrigation treatments for 4 years: T1 (control, surface drip irrigation)—irrigated at 100% ETc throughout the growth cycle, T2 (RDI treatment under SDI)—an irrigation strategy that provided 100% ETc except during the kernel-filling period, when only 20% ETc was provided and T3 (RDI treatment under SDI)—an irrigation strategy that provided 100% ETc except during the kernel-filling period (20% ETc) and post-harvest (50% ETc). A 45% water saving was achieved with strategy SDI T3, while almond production was reduced by only 17%, increasing water use efficiency compared to the control irrigation regime. SDI T3 had fixed overhead costs 9% higher than T1, however, the operating costs were 21% lower for SDI T3 compared to T1. This reduction in costs was basically due to the 45% saving in the cost of water and the corresponding saving in electricity. The break-even point was lower in SDI T3; each kilogram of almonds cost 0.03€ less to produce than in the control conditions. Related to this, the maximum price of water for obtaining profit 0 was 0.21€ m−3 for SDI T3 compared to 0.18€ m−3 for T1, indicating that higher water costs can be borne in SDI T3 (up to 0.03€ m−3 more expensive). Finally the profit/total costs ratio (used as an expression of the overall profitability of the orchard) indicated a greater profitability for the treatment SDI T3 compared to T1 (10.46 and 9.27%, respectively). The RDI strategy SDI T2 did not show economic indices or water use efficiency as much as those of SDI T3. From these results we conclude that RDI applied during kernel-filling and post-harvest under SDI conditions, and specifically the irrigation strategy SDI T3, may be considered economically appropriate in semiarid conditions in order to save water and improve water use efficiency.  相似文献   

5.
The reduction of suspended solids, nutrients, and organic matter loads in drainage water from paddy fields is an important issue for water quality management in closed water areas in Japan. We evaluated the ability of cyclic irrigation to reduce the suspended solids load from paddy fields. In 2006 and 2007, we investigated water and mass balances during the irrigation period in a low-lying paddy-field district neighboring Lake Biwa, which is the largest lake in Japan. We confirmed that cyclic irrigation reduced effluent loads during the puddling season. With cyclic irrigation, 118 kg ha−1 of suspended solids was returned to the paddy fields in 2006 and 199 kg ha−1 in 2007. The effect of cyclic irrigation on the net suspended solids load can be represented by three ratios: the concentration ratio, which represents the ratio of the suspended solids concentration in drainage water to that in lake water; the cyclic irrigation ratio, which represents the ratio of the volume of reused water to that of irrigation water in cyclic irrigation; and the surplus irrigation water ratio, which represents the ratio of the volume of surplus irrigation water to that of irrigation water. The cyclic irrigation ratio and the surplus irrigation water ratio interact to determine the effect of cyclic irrigation on the net suspended solids load. Simultaneously increasing the cyclic irrigation ratio and decreasing the surplus irrigation water ratio will maximize the purification effect on drainage water from paddy fields.  相似文献   

6.
The continuous flow furrow irrigation (COFFI), surge flow furrow irrigation (SUFFI), cutback flow furrow irrigation (CUFFI), variable alternate flow furrow irrigation (VAFFI), and tail water reuse system furrow (TWRSF) techniques with the same inflow rate of 0.072 m3 min−1 were compared in relation to the cotton yield and water use efficiency at a 3-year field study conducted on cotton (Gossypium spp.) in the Southeastern Anatolia Project (GAP) area of Turkey. Yields revealed significant statistical differences between the furrow management techniques (P < 0.05). The maximum yield was obtained from the COFFI treatment (2,630 and 2,920 kg ha−1) in the first 2 years, and from SUFFI and CUFFI treatments (3,690 and 3,780 kg ha−1, respectively) in the last year. There were significant yield reductions, which varied from 10 to 35% in TWRSF and from 11 to 19% in VAFFI treatments although 43 and 28% more water was applied to the TWRSF than to CUFFI and SUFFI treatments, respectively. The average total water use efficiencies (WUEET) varied from 4.14 (VAFFI) to 2.59 (COFFI). The corresponding values were 0.37 and 0.36 kg ha−1 m−3 for CUFFI and SUFFI, respectively. The average irrigation water use efficiency (WUEIR) for CUFFI and SUFFI treatments were 0.30 and 0.23 kg ha−1 m−3, respectively.  相似文献   

7.
Economic incentives reduce irrigation deliveries and drain water volume   总被引：1，自引：0，他引：1  
This paper describes the application of an economic incentive program to achieve water quality objectives by motivating improvements in farm-level water management practices. The program includes farm-specific water allotments, tiered water pricing, and low-interest loans for purchasing irrigation equipment. The implementation of this program in a California water district has resulted in significant reductions in irrigation deliveries and drain water volume. Since the program was implemented, average irrigation depths have declined by 25% on cotton fields, 9% on tomatoes, 10% on cantaloupes, 30% on seed alfalfa, and 29% on grain fields. The average volume of drain water collected each year in subsurface drainage systems has declined from 4.8 million m3 during 1986 through 1989 to 2.6 million m3 during 1990 through 1993. These results confirm that economic incentives can be effective in generating improvements in water quality.  相似文献   

8.
Improved irrigation water use efficiency is an important component of sustainable agricultural production. Efficient water delivery systems such as subsurface drip irrigation (SDI) can contribute immensely towards improving crop water use efficiency and conserving water. However, critical management considerations such as choice of SDI tube, emitter spacing and installation depth are necessary to attain improved irrigation efficiencies and production benefits. In this study, we evaluated the effects of subsurface drip tape emitter spacing (15, 20 and 30 cm) on yield and quality of sweet onions grown at two locations in South Texas—Weslaco and Los Ebanos. Season-long cumulative crop evapotranspiration (ETc) was 513 mm in Weslaco and 407 mm at Los Ebanos. Total crop water input (rain + irrigation) at Weslaco was roughly equal to ETc (92% ETc) whereas at Los Ebanos, water inputs exceeded ETc by about 35%. Onion yields ranged from 58.5 to 70.3 t ha−1 but were not affected by drip tube emitter spacing. Onion pungency (pyruvic acid development) and soluble solids concentration were also not significantly influenced by treatments. Crop water use efficiency was slightly higher at Weslaco (13.7 kg/m3) than at Los Ebanos (11.7 kg/m3) partly because of differences in total water inputs resulting from differences in irrigation management. The absence of any significant effects of drip tape emitter spacing on onion yield may be due to the fact that irrigation was managed to provide roughly similar irrigation amounts and optimum soil moisture conditions in all treatments.  相似文献   

9.
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.  相似文献   

10.
Research on crop response to deficit irrigation is important to reduce agricultural water use in areas where water is a limited resource. Two field experiments were conducted on a loam soil in northeast Spain to characterize the response of maize (Zea mays L.) to deficit irrigation under surface irrigation. The growing season was divided into three phases: vegetative, flowering and grain filling. The irrigation treatments consisted of all possible combinations of full irrigation or limited irrigation in the three phases. Limited irrigation was applied by increasing the interval between irrigations. Soil water status, crop growth, above-ground biomass, yield and its components were measured. Results showed that flowering was the most sensitive stage to water deficit, with reductions in biomass, yield and harvest index. Average grain yield of treatments with deficit irrigation around flowering (691 g m−2) was significantly lower than that of the well-irrigated treatments (1069 g m(2). Yield reduction was mainly due to a lower number of grains per square metre. Deficit irrigation or higher interval between irrigations during the grain filling phase did not significantly affect crop growth and yield. It was possible to maintain relatively high yields in maize if small water deficits caused by increasing the interval between irrigations were limited to periods other than the flowering stage. Irrigation water use efficiency (IWUE) was higher in treatments fully irrigated around flowering.  相似文献   

11.
A detailed district and agro-ecoregional level study comprising the 604 districts of India was undertaken to (i) identify dominant rainfed districts for major rainfed crops, (ii) make a crop-specific assessment of the surplus runoff water available for water harvesting and the irrigable area, (iii) estimate the efficiency of regional rain water use and incremental production due to supplementary irrigation for different crops, and (iv) conduct a preliminary economic analysis of water harvesting/supplemental irrigation to realize the potential of rainfed agriculture. A climatic water balance analysis of 225 dominant rainfed districts provided information on the possible surplus runoff during the year and the cropping season. On a potential (excluding very arid and wet areas) rainfed cropped area of 28.5 million ha, a surplus rainfall of 114 billion m3 (Bm3) was available for harvesting. A part of this amount of water is adequate to provide one turn of supplementary irrigation of 100 mm depth to 20.65 Mha during drought years and 25.08 Mha during normal years. Water used in supplemental irrigation had the highest marginal productivity and increase in rainfed production above 12% was achievable even under traditional practices. Under improved management, an average increase of 50% in total production can be achieved with a single supplemental irrigation. Water harvesting and supplemental irrigation are economically viable at the national level. Net benefits improved by about threefold for rice, fourfold for pulses and sixfold for oilseeds. Droughts have very mild impacts on productivity when farmers are equipped with supplemental irrigation.  相似文献   

12.
Irrigation performance assessments are required for hydrological planning and as a first step to improve water management. The objective of this work was to assess seasonal on-farm irrigation performance in the Ebro basin of Spain (0.8 million ha of irrigated land). The study was designed to address the differences between crops and irrigation systems using irrigation district data. Information was only available in districts located in large irrigation projects, accounting for 58% of the irrigated area in the basin. A total of 1617 records of plot water application (covering 10,475 ha) were obtained in the basin. Average net irrigation requirements (IRn) ranged from 2683 m3 ha−1 in regulated deficit irrigation (RDI) vineyards to 9517 m3 ha−1 in rice. Average irrigation water application ranged from 1491 m3 ha−1 in vineyards to 11,404 m3 ha−1 in rice. The annual relative irrigation supply index (ARIS) showed an overall average of 1.08. Variability in ARIS was large, with an overall standard deviation of 0.40. Crop ARIS ranged between 0.46 and 1.30. Regarding irrigation systems, surface, solid-set sprinkler and drip irrigated plots presented average ARIS values of 1.41, 1.16 and 0.65, respectively. Technical and economic water productivities were determined for the main crops and irrigation systems in the Aragón region. Rice and sunflower showed the lowest productivities. Under the local technological and economic constraints, farmers use water cautiously and obtain reasonable (yet very variable) productivities.  相似文献   

13.
Summary In this paper the soil water balance model developed and tested in Part III (Mason and Smith, 1980) for soybeans grown in the variable rainfall environment of the Namoi Valley of New South Wales was used to investigate the potential advantages of a computer-based system of irrigation scheduling. The advantages were evaluated using historical rainfall data for the 25 seasons from 1953/54 to 1977/78. The effects on irrigation efficiency of soil water holding capacity, the allowable soil water deficit prior to irrigation, and ordering irrigation water in advance were evaluated with the model. Reducing the allowed deficit prior to irrigation by 20% compared to the recommended level increased the number of irrigations by an average of 2.8 per year and irrigation requirements by 0.73 X 103 m3 ha–1. The need to order water 6 days in advance because of delays in delivery also increased requirements by 1.46 X 103 m3 ha–1 due to a reduced ability to utilize natural rainfall. Average farm irrigation efficiencies calculated from actual pumping records were found to be low by world standards for the 3-year period 1975/76 to 1977/78. It was concluded that if increased production per unit of water became a high priority in the Namoi Valley, then irrigation efficiency for the three year period discussed could have been increased from 35 to 47%, a saving of 1.3 X 103 m3 ha–1 year–1.  相似文献   

14.
In this study, a regional irrigation schedule optimization method was proposed and applied in Fengqiu County in the North China Plain, which often suffers serious soil water drainage and nitrogen (N) leaching problems caused by excessive irrigation. The irrigation scheduling method was established by integrating the ‘checkbook irrigation method’ into a GIS-coupled soil water and nitrogen management model (WNMM) as an extension. The soil water and crop information required by the checkbook method, and previously collected from field observations, was estimated by the WNMM. By replacing manually observed data with simulated data from WNMM, the application range of the checkbook method could be extended from field scale to regional scale. The WNMM and the checkbook irrigation method were both validated by field experiments in the study region. The irrigation experiment in fluvo–aquic soil showed that the checkbook method had excellent performance; soil water drainage and N leaching were reduced by 83.1 and 85.6%, respectively, when compared with local farmers’ flood irrigation. Using the validated WNMM, the performance of checkbook irrigation in an entire winter wheat and summer maize rotation was also validated: the average soil water drainage and N leaching in four types of soils decreased from 331 to 75 mm year−1 and 47.7 to 9.3 kg ha−1 year−1, respectively; and average irrigation water use efficiency increased from 26.5 to 57.2 kg ha−1 mm−1. The regional irrigation schedule optimization method based on WNMM was applied in Fengqiu County. The results showed a good effect on saving irrigation water, decreasing soil water drainage and then saving agricultural inputs. In a typical meteorological year, it could save >110 mm of irrigation water on average, translating to >7.26 × 107 m3 of agricultural water saved each year within the county. Annual soil water drainage was reduced to <143 mm and N leaching to <27 kg ha−1 in most soils, all of which were significantly lower than local farmers’ flood irrigation. In the mean time, crop yield also had an average increase of 2,890 kg ha−1 when checkbook irrigation was applied.  相似文献   

15.
Decreasing in water availability for cotton production has forced researchers to focus on increasing water use efficiency by improving either new drought-tolerant cotton varieties or water management. A field trial was conducted to observe the effects of different drip irrigation regimes on water use efficiencies (WUE) and fiber quality parameters produced from N-84 cotton variety in the Aegean region of Turkey during 2004 and 2005. Treatments were designated as full irrigation (T100, which received 100% of the soil water depletion) and those that received 75, 50 and 25% of the amount received by treatment T100 on the same day (treatments T75; T50 and T25, respectively). The average seasonal water use values ranged from 265 to 753 mm and the average seed cotton yield varied from 2550 to 5760 kg ha−1. Largest average cotton yield was obtained from the full irrigation treatment (T100). WUE ranged from 0.77 kg m−3 in the T100 to 0.98 kg m−3 in the T25 in 2004 growing season and ranged from 0.76 kg m−3 in the T100 to 0.94 kg m−3 in the T25 in 2005 growing season. The largest irrigation water use efficiency (IWUE) was observed in the T25 (1.46 kg m−3), and the smallest IWUE was in the T100 treatment (0.81 kg m−3) in the experimental years. A yield response factor (ky) value of 0.78 was determined based on averages of two years. Leaf area index (LAI) and dry matter yields (DM) increased with increasing water use for treatments. Fiber qualities were influenced by drip irrigation levels in both years. The results revealed that well-irrigated treatments (T100) could be used for the semi-arid climatic conditions under no water shortage. Moreover, the results also demonstrated that irrigation of cotton with drip irrigation method at 75% level (T75) had significant benefits in terms of saved irrigation water and large WUE indicating a definitive advantage of deficit irrigation under limited water supply conditions. In an economic viewpoint, 25.0% saving in irrigation water (T75) resulted in 34.0% reduction in the net income. However, the net income of the T100 treatment is found to be reasonable in areas with no water shortage.  相似文献   

16.
With the present regime of irrigation supplies to the Fayoum province of Egypt, there is no real problem regarding the increase in water levels of Lake Qaroun which is the major recipient of drainage water. Future developments should therefore concentrate on solving the problem of peak supplies for agricultural use. It has been proposed to remedy the shortage caused by further agricultural developments by increasing the system capacity by 20%. There is, however, an alternative approach which requires no engineering work; this is to change the cropping pattern by introducing rotations which reduce peak water requirements.A simplified water balance based on available data is prepared in order to acquire a better understanding of the whole situation and to set up a strategy for future agricultural development.The developed strategy takes into account the limitations imposed by the closed system of the Fayoum basin such as the irrigation efficiency, the Lake Qaroun optimum water level, land reclamation possibilities, Wadi Rayan drainage surplus, and salt concentrations in Lake Qaroun.  相似文献   

17.
Actual evapotranspiration (ETc) of three mature sweet orange orchards (cv. Salustiana and Washington Navel on sour orange), under border irrigation and typical cultural practices was measured by the water balance method during 1981 to 1984. Soil water content was measured at 7 to 10 day intervals using a neutron meter and soil sampling of the 0–10 cm surface layer. Zero flux plane was calculated by measurements with mercury tensiometers. Irrigation water in these and other 5 similar orchards was measured by broad crested weirs. Rainfall and other climatic data for calculation of reference evapotranspiration by FAO's methods (ETo) were collected in a nearby meteorological station. Average yearly ETc ranged from 750 to 660 mm and mean monthly maximum was 3.7 and 3.2 mm/day in July for Salustiana and W. Navel orchards, respectively.ETo estimates for the different methods used were highly correlated (r 20.94). Monthly crop coefficients (Kc) based on pan evaporation ranged from 0.5–0.6 in spring and summer to 0.8 in autumn and were about 10% higher than those for Penman or radiation methods. Average annual Kc for the three plots studied was 0.64, 0.61 and 0.51, respectively, and correlated well (r 2=0.99) with tree ground cover. Irrigation efficiency was about 50% for orchards with soils with less water holding capacity and more applied water per irrigation and 70–80% in orchards with deeper soils or with a higher water holding capacity. Increasing irrigation frequency and applying smaller amounts of water per irrigation with good uniformity can improve on-farm irrigation efficiency.  相似文献   

18.
To improve water saving and conservation in irrigated agriculture, a range of field evaluation experiments was carried out with various furrow irrigation treatments in cotton fields to estimate the possibilities of improving furrow irrigation performances under conditions of Central Fergana Valley, Uzbekistan. The research consisted in comparing surge and continuous-flow in long furrows and adopting alternate-furrow irrigation. The best results were achieved with surge-flow irrigation applied to alternate furrows. Field data allowed the calibration of a surface irrigation model that was used to identify alternative management issues. Results identified the need to better adjust inflow rates to soil infiltration conditions, cut-off times to the soil water deficits and improving irrigation scheduling. The best irrigation water productivity (0.61 kg m−3) was achieved with surge-flow on alternate furrows, which reduced irrigation water use by 44% (390 mm) and led to high application efficiency, near 85%. Results demonstrated the possibility for applying deficit irrigation in this region.  相似文献   

19.
The response of sunflower (Helianthus annuus L.) to 14 irrigation treatments in a sub-humid environment (Bursa, Turkey) was studied in the field for two seasons. A rainfed (non-irrigated) treatment as the control and 13 irrigation treatments with full and 12 different deficit irrigations were applied to the hybrid Sanbro (Novartis Seed Company) planted on clay soil, at three critical development stages: heading (H), flowering (F) and milk ripening (M). The yield increased with irrigation water amount, and the highest seed yield (3.95 t ha−1) and oil yield (1.78 t ha−1) were obtained from the HFM treatment (full irrigation at three stages); 82.9 and 85.4% increases, respectively, compared to the control. Evapotranspiration (ET) increased with increased amounts of irrigation water supplied. The highest seasonal ET (average of 652 mm) was estimated at the HFM treatment. Additionally, yield response factor (k y) was separately calculated for each, two and total growth stages, and k y was found to be 0.8382, 0.9159 (the highest value) and 0.7708 (the lowest value) for the total growing season, heading, and flowering-milk ripening combination stages, respectively. It is concluded that HFM irrigation is the best choice for maximum yield under the local conditions, but these irrigation schemes must be re-considered in areas where water resources are more limited. In the case of more restricted irrigation, the limitation of irrigation water at the flowering period should be avoided; as the highest water use efficiency (WUE) (7.80 kg ha−1 mm−1) and irrigation water use efficiency (IWUE) (10.19 kg ha−1 mm−1) were obtained from the F treatment.  相似文献   

20.
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.  相似文献   

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