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1.
Influence of season to season variability in weather on irrigation scheduling of wheat: A simulation study 总被引：2，自引：0，他引：2
Summary There is an increasing demand from farmers for irrigation scheduling advice. Where rainfall and evapotranspiration vary little from year to year, advice on a fixed irrigation schedule based on mean climatic data can be given. However where significant year to year variability in weather occurs a more flexible approach using actual weather data to predict the current level of soil water and mean climatic data to forecast the future rate of depletion and hence irrigation date may be needed. A technique for deciding the most appropriate scheduling approach was tested by using a simple model of crop growth combined with a soil water balance model to simulate year to year variability in scheduling advice. This technique was applied to irrigated wheat using a set of climatic data from 1968 to 1978 for Griffith in the Murrumbidgee Irrigation Area of New South Wales, Australia. A typical sowing date in early June was used and simulated irrigations were scheduled at an allowable soil water depletion (ASWD) of 62 mm for maximum yield and 93 mm for 80% of maximum. The analysis predicted that weather variability between years would cause the number of irrigations to vary from 2 to 7 for ASWD=62 mm and 1 to 4 for ASWD=93 mm. The interval between irrigations varied from 12 to 30 days, for ASWD=62 mm and from 16 to 28 days, for ASWD=93 mm. The first irrigation occurred between 76 and 131 days from sowing for ASWD=62 mm and from 100 to 140 days from sowing for ASWD=93 mm. The date of the last irrigation was similarly variable. This high degree of variability in the times and frequency of irrigations indicated that in south-eastern Australia accurate irrigation scheduling advice can only be given by using a flexible model using both actual and mean climatic data. A fixed schedule based on mean climatic data would lead to an inefficient use of water caused by the mistiming of irrigations. 相似文献
2.
Crop response to deficit irrigation is an important consideration for establishing irrigation management strategies when water supplies are limited. This study evaluated the response of native spearmint to water deficits applied using overhead sprinklers in eastern Washington, US. Five levels of irrigation were applied ranging from full irrigation (100%) to 5% of weekly averaged full crop water needs. Soil water monitoring with soil water balance was used to estimate soil water deficits for irrigation scheduling and soil water use. Mint oil yields, oil components, dry matter production, and the water-use efficiency of the spearmint were assessed. There was significant reduction in fresh mint hay (harvested biomass) yield with increasing water deficit. However, spearmint oil yields remained generally uniform across irrigation treatments at the first cutting but decreased at the driest plots during the second harvest due to a loss of plant stand. The wet harvest index and water-use efficiency improved significantly for both harvests with increasing water deficit. Hay yield, oil yield, wet harvest index, and water-use efficiency are pooled across sides and replicate blocks to provide trends with changes in maximum evapotranspiration. The three major monoterpenes show changes suggesting less mature oil yields. The study demonstrates the feasibility of sustaining native spearmint yields under managed deficit irrigations for deficits not lower than 0.5 ETc. 相似文献
3.
Summary An investigation was made of the irrigation requirements of cotton grown in a sub-humid environment with significant but highly variable rainfall. In the first year of the study, no additional yield benefits accrued to subsequent irrigations following a pre-emergent irrigation due to above average rainfall (550 mm) throughout the growing season. In the second year a similar rainfall amount (502 mm) fell but significant yield increases to irrigation resulted due to the uneven distribution of the rainfall. The main effect was associated with later rains which influenced the number of bolls set. The maximum amount of water extracted by cotton from a deep grey cracking clay was 178 mm. It was found that 70% of this amount could be depleted before irrigation without loss of yield. Crop evapotranspiration varied from 607 mm with no irrigation after emergence to 775 mm following three irrigations. Irrigation was associated with significant losses from rainfall runoff. Too frequent irrigation creates a risk that soil will be too wet to permit utilisation of natural rainfall. Therefore, the use of soil water information to maximise the interval between irrigation is proposed as a necessary basis for efficient irrigation management. 相似文献
4.
Plant water relations, tree growth, and yield components of mature almond trees [Prunus dulcis (Mill.) Webb cv. Nonpareil] were evaluated in response to ranges of irrigation cutoff durations immediately prior to harvest
and to postharvest water deprivation. The preharvest cutoff regimes consisted of eight treatments that terminated irrigation
from 8 to 57 days prior to tree shaking, resulting in 297 mm less preharvest-applied water for the longest cutoff regime.
Postharvest irrigation totaled 206 mm. Predawn leaf water potential (LWP) declined rapidly after irrigation cutoff and reached
−4.0 MPa prior to harvest in the most severe preharvest treatment. This resulted in reduced tree growth and near complete
canopy defoliation. Individual kernel weight and full hull splitting were reduced by up to 17.2% and 71.1%, respectively,
by the preharvest cutoff regimes, while bark damage due to mechanical shaking and fruit removal was unaffected. Hull rot at
harvest was virtually eliminated with the longer preharvest cutoff durations. Depriving trees of postharvest irrigation had
a greater impact on tree productivity than the preharvest irrigation cutoffs, even though the amount of postharvest-deprived
water was less than that which occurred with the more severe preharvest cutoffs. In the season following postharvest water
deprivation, bloom density and fruit set were reduced by up to 52.2% and 94.3%, respectively. This resulted in fruit load
and kernel yield reductions of up to 76.7% and 73.6%, respectively. Even with the latest preharvest cutoff regime, fruit load
and kernel yield were significantly lower without postharvest irrigation. We postulate that the sensitivity to postharvest
water deficits is due to the late reproductive bud differentiation of almond, which may damage primordial flower parts and/or
accelerate the emergence of the stamens during bloom, thus decreasing their pollen receptivity. Since postharvest water deficits
are more damaging to sustained productivity than water deficits prior to harvest, growers with limited water supplies should
bias irrigation towards the postharvest period.
Received: 15 September 1999 相似文献
5.
灌排方案对避雨番茄需水特性与产量的影响 总被引：5，自引：0，他引：5
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08 m的处理较埋深06 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107～271 mm／d,始花坐果期日蒸发蒸腾量变化范围为160～309 mm／d,果实成熟与采收期日蒸发蒸腾量变化范围为178～335 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. 相似文献
6.
Summary The effect of various irrigation regimes on soil aeration was tested in a two-year experiment with 15 year-old apple trees growing in soil containing 67% clay. Irrigation was applied by sprinklers at four intervals ranging from 3 to 18 days and by trickle irrigation every 7 days. Each treatment received a total of 800–850 mm water from May until September. Irrigation by sprinkling at 7 day intervals appeared to be optimal for fruit growth. Less frequent irrigations resulted in smaller fruits; sprinkling at 3–4 day intervals, as well as trickle irrigation reduced the fruit growth rate in July. Leaves from plots irrigated once every 3–4 days had a low chlorophyll content and accumulated relatively large amounts of ethanol, particularly when grafted on the Khashabi rootstock, which is highly susceptible to damage caused by inadequate soil aeration. With increasing intervals between irrigations, the resistance of the leaf surface to the diffusion of water vapour measured prior to irrigation increased, and water loss relative to that from an evaporation pan decreased. Sprinkling at intervals of 14 days resulted in maximal, and at 3–4 days in minimal, air contents of the soil when calculated as averages for the total period of irrigation. The decrease in soil air content with very frequent irrigations was particularly marked in the upper soil layer; this same layer also had a relatively low air content near the emitters in trickle irrigation. After each irrigation, relatively large amounts of ethylene accumulated in the soil atmosphere, indicating inadequate soil aeration, particularly with sprinkling intervals of 3–4 days and at a depth of 30 cm. However, the influence of the irrigation treatments on the oxygen and carbon dioxide contents of the soil atmosphere was small and not consistent. 相似文献
7.
Estimates of the effects of alternative discrete irrigation water scheduling options on consumptive use or evapotranspiration
and on crop yield are developed for a northeastern Colorado case study. The analysis proceeds from the premise that farmers,
rather than considering irrigation water as a continuously variable input, tend to treat irrigations as discrete events, and
make scheduling decisions as choices among numbers of irrigations of approximately equal volume. The van Genuchten-Hanks model
is employed to develop a transient-state water-crop production function model. Results for two crops – corn grain and edible
dry beans – are presented here. Findings are that the effect of the number of irrigations on evapotranspiration and yield
per hectare varies widely, depending upon the timing of applications. When farmers can choose the optimal timing of irrigations,
a reduced number of irrigations has a relatively limited adverse effect on crop production until irrigations are reduced to
less than four per season. However, there are many situations in which an inability to apply water can result in a very large
reduction from potential maximum yield, particularly if water is withheld early in the season and/or during the rapid growth
period of the crops. In many contexts of irrigation water management, water policy analysts will wish to consider the more
realistic discrete-input simulation model for policy evaluation.
Received: 1 November 1996 相似文献
8.
Experiments were undertaken at CCS Haryana Agricultural University Farm, Sirsa (India) to estimate the optimum irrigation
schedule for cotton resulting in minimum percolation losses. The sprinkler line source technique was adopted for creating
various irrigation regimes at different crop growth stages. The SWASALT (Simulation of Water And SALT) model after calibration
and validation provided water balance components. The wa-ter management response indicators (WMRI's) such as transpiration
efficiency Et/(Irr + P), relative transpiration Et/Etp, evapotranspiration efficiency ET/(Irr + P), soil moisture storage change ΔW/Wint (deficit/excess) and percolation loss Perc/(Irr. + P) were evaluated using water balance components as estimated by the simulation
study. Under limited water supply conditions, the optimum irrigation depth was found to be 57 mm at crop growth stages with
pre-sowing and 1st irrigation of 120 mm and 80 mm respectively for sandy clay loam underlain by sandy loam soil (Type I). The corresponding
values of relative transpiration, transpiration efficiency and evapotranspiration efficiency were 0.65, 0.65 and 0.89 respectively.
The crop yield varied linearly with increasing irrigation depth which was evident from increase in relative transpiration
with increasing depth of water application. However, increased depth of irrigation resulted in less moisture utilisation from
soil storage (20% depletion at 40 mm depth and 4.4% moisture built up at 100 mm depth). The extended simulation study for
sandy soil underlain by loamy sand (Type II) indicated that two pre-sowing irrigations each 40 mm and subsequent irrigations
of 40 mm at an interval of 20 days depending upon rainfall were optimum. This irrigation scenario resulted in zero percolation
loss accompanied by 74% relative transpiration and 14 per cent soil moisture depletion.
Received: 20 November 1995 相似文献
9.
《Agricultural Water Management》2006,79(3):312-320
Shrinking water resources in northwest India calls for diversification from a rice–wheat cropping system to low-water-requiring crops and development of water-efficient technologies in Punjab state. Chickpea, because of its lower water demand (evapotranspiration) and irrigation requirement has been identified as a suitable alternate crop to wheat. Simulations, averaged over 18 years, using the CROPMAN model indicated that the yield of chickpea on coarse- to medium-textured soils was higher in a rice–chickpea cropping system compared with maize–chickpea and mung–chickpea systems because of increased availability of water. Yield response of chickpea to irrigation depended upon soil texture, the timings and number of irrigations. The optimum yield (2 t ha−1) on coarse- to medium-textured soils after rice can be obtained with one heavy pre-plant and two post-plant irrigations, i.e., one in mid-February and one in mid-March synchronizing irrigations with flowering and grain development stages. Grain yield with irrigation water followed a quadratic function and linear with evapotranspiration. Water use efficiency and evapotranspiration was curvilinear. Grain yield was significantly sensitive to water stress during the pod setting to grain development period irrespective of soil texture. 相似文献
10.
Deficit irrigation in maize for reducing agricultural water use in a Mediterranean environment 总被引：4，自引：0，他引：4
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.
Summary Sugar beets (Beta vulgaris L.) were grown on a Millville silt loam soil at Logan, Utah to study the relationships between yield (total dry matter, fresh root, and sucrose) and various levels of irrigation simulating different types of limited irrigation under drought conditions. There were four harvest dates. A model, PLANTGRO, was tested for yield prediction under the imposed conditions. A line source sprinkler irrigation system which applied irrigation water from an excess to a zero amount, was used to impose the various levels of irrigation. Irrigation was continued throughout the season on half of the area and terminated at mid-season on the other half. For both irrigation treatments, yield responses to irrigation levels were large. Unlike continuous irrigation throughout the season, when irrigation was terminated in mid-season, there was no increase in yield (total dry matter, fresh root, or sucrose) from harvest 1 to harvest 4. The relation of yield to termination of irrigation depended on the amount of stored soil water at the time of termination. Yield and relative yield exhibited a strong linear relationship with ET. Percent sucrose was not significantly affected by irrigation regimes or harvest date, but tended to increase as amount of applied irrigation water increased. The model PLANTGRO gave good predictions for relative yields of fresh roots, sucrose, and total dry matter under full-season irrigation. The relative yield relations of fresh roots, sucrose and total dry matter were similar. Where irrigation was terminated in mid-season the model slightly under-predicted yield at high irrigation levels.Contribution from Utah Agricultural Experiment Station, Utah State University, UT 84322, USA 相似文献
12.
A 4-year field experiment was conducted in a semi-arid area to evaluate the response of each furrow and alternate furrow irrigation
in wheat-cotton system using irrigation waters of different qualities in a calcareous soil. Irrigation was applied to each
and alternate furrow of bed-planted wheat followed by ridge-planted cotton for comparison with standard check-basin method
of irrigation to both the crops. These methods of irrigation were evaluated under three water qualities namely good quality
canal water (CW), poor quality tube well water (TW) and pre-sowing irrigation to each crop with CW and all subsequent irrigations
with TW (CWpsi + TW). The pooled results over 4 years revealed that wheat grain yield was not affected significantly with
quality of irrigation water, but significant yield reduction was observed in alternate bed irrigation under canal water and
tube well water irrigations. In cotton, poor quality tube well water significantly reduced the seed cotton yield in all the
three methods of planting. The pre-sowing irrigation with canal water and all subsequent irrigations with tube well water
improved the seed cotton yield when compared with tube well water alone. However, this yield increase was significant only
in alternate furrow irrigation, and the yield obtained was on a par with yield under alternate furrow in CW. When compared
to check-basin irrigation, each furrow and alternate furrow irrigation resulted in a saving of 30 and 49% of irrigation water
in bed-planted wheat, whereas the corresponding savings in ridge-planted cotton were 20 and 42%, respectively. Reduced use
of irrigation water under alternate furrow, without any significant reduction in yield, resulted in 28.1, 23.9 and 43.2% higher
water use efficiency in wheat under CW, TW and CWpsi + TW, respectively. The corresponding increase under cotton was 8.2,
2.1 and 19.5%. The implementation of alternate furrow irrigation improved the water use efficiency without any loss in yield,
thus reduced use of irrigation water especially under poor quality irrigation water with pre-sowing irrigation with canal
water reduced the deteriorating effects on yield and soil under these calcareous soils. 相似文献
13.
Summary The effect of the soil water potential on pod yield of snap beans grown with a series of irrigation frequencies was studied over two seasons. The treatments were to furrow-irrigate either weekly or fortnightly during the preflowering period, and each treatment then received weekly or fortnightly irrigations to harvest. These treatments were compared with trickle irrigation applied daily in the first season and every second day in the second season. The irrigation frequencies during the pre-flowering period did not influence the pod yield. However, in the second season plants given the trickle irrigation treatment produced more early flowers and set pods earlier than those in the other treatments. Consequently the pods were harvested three days earlier from plants on this treatment.Pod yield was determined by the irrigation treatments applied after flowering. The highest yield was similar in each season (16.7 t ha–1) and was produced under trickle irrigation. Fortnightly irrigations during the pod-fill phase reduced yield by 56% in the first season and 41% in the second season when compared with trickle irrigation. The pod yield was reduced by 0.5 t ha–1 each day the soil water potential at 30 cm depth was less than –50 kPa. This relationship accounted for about 77% of the variation in pod yield. 相似文献
14.
Summary In a previous study conducted at the University of California at Riverside, it was shown that water use of cowpea could be reduced while maintaining seed yields by withholding irrigation during the vegetative stage in a rain-free environment, and then irrigating when estimates based on potential evapotranspiration, indicated 40% depletion of available moisture in 90-cm depth of soil. The general applicability of this efficient irrigation management method was tested by experiments conducted at the West Side Field Station in the San Joaquin Valley of California with six irrigation treatments, three different row spacings (single rows on 76- and 102-cm beds, and double rows on a 102-cm bed), a semi-erect cultivar of cowpea (Vigna unguiculata [L.] Walp.), and a prostrate cultivar of lima bean (Phaseolus lunatus L.).Withholding irrigation during the vegetative stage following pre-irrigation substantially reduced dry matter at anthesis (–17% to –38%) and water use (–101 mm) of cowpea, but did not influence seed yield or shoot dry matter at harvest for either cowpea or lima bean. Increasing the irrigation interval until 75% nominal depletion of available water in 90-cm depth of soil reduced water use (–139 cm), but did not affect seed yield of cowpea. Lima bean, however, showed a significant decrease in shoot dry matter production (–17%) and in seed production (–18%) at the longest irrigation interval involving 75% nominal depletion. The different row spacings used in this experiment did not affect shoot dry matter or seed production of the semi-erect cowpea. However, shoot dry matter and seed yield were significantly greater for the prostrate lima bean grown with double rows on a 102-cm bed. Seed yield was 46% and 18% greater than with single rows on 76-cm and 102-cm beds, respectively. Generally, variations in seed yields of lima bean were positively correlated with variations in shoot dry matter production.Nominal depletion of available soil water provided a practical method for scheduling irrigations, but the results with cowpea indicated that the critical level, which resulted in the greatest reductions in water use while maintaining maximum seed yield varied from 40% (at Riverside) to 75% (at West Side Field Station). Additional methods are needed to fine-tune irrigation which is based mainly on nominal depletion of available water. Generally, pressure chamber estimates of leaf water potential exhibited too little variation among plants subjected to different irrigation treatments for it to be useful for fine-tuning irrigation schedules for either cowpea or lima bean. However, differences in temperature between canopy and air, when expressed as a function of either vapor pressure deficit or canopy temperature, and related to percent reduction in yield, appeared to have sufficient resolution to provide a practical method for fine-tuning irrigation schedules for cowpea during flowering and pod-filling, but not lima bean. Normalizing temperature differences with vapor pressure deficit was more effective, but normalizing with canopy temperatures is more convenient because it does not require a measurement of air humidity. 相似文献
15.
16.
Effects of irrigation strategies and soils on field grown potatoes: Yield and water productivity 总被引：1，自引：0，他引：1
Seyed Hamid Ahmadi Mathias N. Andersen Rolf T. Poulsen Ali Reza Sepaskhah 《Agricultural Water Management》2010,97(11):1923-1290
Yield and water productivity of potatoes grown in 4.32 m2 lysimeters were measured in coarse sand, loamy sand, and sandy loam and imposed to full (FI), deficit (DI), and partial root-zone drying (PRD) irrigation strategies. PRD and DI as water-saving irrigation treatments received 65% of FI after tuber bulking and lasted for 6 weeks until final harvest. Analysis across the soil textures showed that fresh yields were not significant between the irrigation treatments. However, the same analysis across the irrigation treatments revealed that the effect of soil texture was significant on the fresh yield and loamy sand produced significantly higher fresh yield than the other two soils, probably because of higher leaf area index, higher photosynthesis rates, and “stay-green” effect late in the growing season. More analysis showed that there was a significant interaction between the irrigation treatments and soil textures that the highest fresh yield was obtained under FI in loamy sand. Furthermore, analysis across the soil textures showed that water productivities, WP (kg ha−1 fresh tuber yield mm−1 ET) were not significantly different between the irrigation treatments. However, across the irrigation treatments, the soil textures were significantly different. This showed that the interaction between irrigation treatments and soil textures was significant that the highest significant WP was obtained under DI in sandy loam. While PRD and DI treatments increased WP by, respectively, 11 and 5% in coarse sand and 28 and 36% in sandy loam relative to FI, they decreased WP in loamy sand by 15 and 13%. The reduced WP in loamy sand was due to nearly 28% fresh tuber yield loss in PRD and DI relative to FI even though ET was reduced by 9 and 11% in these irrigation treatments. This study showed that different soils will affect water-saving irrigation strategies that are worth knowing for suitable agricultural water management. So, under non-limited water resources conditions, loamy sand produces the highest yield under full irrigation but water-saving irrigations (PRD and DI) are not recommended due to considerable loss (28%) in yield. However, under restricted water resources, it is recommended to apply water-saving irrigations in sandy loam and coarse sand to achieve the highest water productivity. 相似文献
17.
为了分析不同间歇时间和矿化度对黄河三角洲粉壤土水分入渗特征及盐分分布的影响,进行了咸淡水交替灌溉的室内土柱试验,设置4种间歇时间(0, 30, 60, 90 min)和3种咸水矿化度(3,6,9 g/L),分析了累积入渗量、入渗历时、土壤水盐分布等参数变化.结果表明:相同入渗水量下,咸淡水交替灌溉的入渗历时随间歇时间的增加而显著增大.当咸水矿化度为3,6,9 g/L时,咸淡水交替灌溉处理的平均土壤含水率差异不具有统计学意义,但咸水矿化度为3 g/L处理的平均土壤含盐量低于咸水矿化度为6和9 g/L处理,且间歇90 min的平均土壤含盐量远低于其他处理.因此,当咸水矿化度为3 g/L,间歇时间较长的灌溉方式有利于降低土壤盐分. 相似文献
18.
Deficit irrigation after harvest has been proven to be a more profitable strategy for producing loquats due to its effects on promoting earlier flowering and harvest date next season. To determine water savings which most advance flowering and harvest dates, an experiment was established to compare phenology, fruit quality and yield in ‘Algerie’ loquats over two consecutive seasons. In this experiment some trees were programmed to receive 50%, 25% or 0% of the water applied to controls (RDI50%, RDI25%, and RDI0%, respectively) from mid-June to the end of July (6 weeks). Fully irrigated trees acted as first controls while trees undergoing previously tested postharvest deficit irrigation (25% of water applied to controls; RDILong) from early June up to the end of August (13 weeks of RDI total) acted as second controls. All deficit irrigation treatments promoted earlier flowering when compared to fully irrigated trees; the greatest advancement in full bloom date (27 days) was achieved with severe short term RDI (RDI0% and RDI25%). The trees suffering an extended period of water stress advanced full bloom date but to a lesser extent (13 and 18 days; 2004/2005 and 2005/2006, respectively). Earlier bloom derived in an earlier harvest date without detrimental effects on fruit quality and productivity. In this regard, the most severe RDI (RDI0%) advanced mean harvest date the most (7 and 9 days, depending on the season), and increased the percentage of precocious yield to the highest extent. Productivity was not diminished by reduced irrigation in either season. Fruit size and grading was enhanced thanks to RDI in both seasons. Earliness and better fruit class distribution under RDI also improved fruit value and gross revenue enabling farmers both to increase earning and economize on water. 相似文献
19.
W.R. Norman W.H. Shayya A.S. Al-Ghafri I.R. McCANN 《Irrigation and Drainage Systems》1997,12(1):35-48
This paper reports on results from a case study on water management within a traditional, falaj irrigation system in northern Oman. In the planning and design of regional irrigation development programs, generalized assumptions are frequently made as to the efficiency of traditional surface irrigation systems. Although qualitative accounts abound, very little quantitative research has been conducted on on-farm water management within falaj systems. Daily irrigation applications and crop water use was monitored during an 11-month period among 6 farm holdings at Falaj Hageer in Wilayat Al-Awabi. Contrary to the frequent assumptions that all surface irrigation systems incur unnecessarily high water losses, on-farm ratios of crop water demand to irrigation supply were found to be relatively high. Based on actual crop water use, irrigation demand/supply ratios among monitored farms varied from 0.60 to 0.98, with a mean of 0.79. Examination of the soil moisture budget indicates that during most irrigations of wheat (cultivated in the low evapotranspiration months of October–March) sufficient water is applied for the shallow root zone to attain field capacity. With the exception of temporary periods of high falaj delivery flows or periods of rainfall, field capacity is usually not attained during irrigations within the more extensive root zones of date palm farms. The data presented in this paper should provide a better understanding of water use performance by farmers within traditional falaj systems. Moreover, these data should also serve to facilitate more effective development planning for irrigation water conservation programs in the region. 相似文献
20.
《Agricultural Water Management》1997,32(3):285-291
The response of wheat (Triticum aestiuum L.) to varying depths of irrigation, quantity of water applied and to the drainage conditions was studied in 2 m × 2 m × 2 m size lysimeters filled in with a sandy loam soil. Saline water with an electrical conductivity of 8.6 dS m−1 was used for irrigation. The treatments included four irrigations of 5 cm depth, four irrigations of 7 cm, and three irrigations of 9 cm, scheduled on the basis of cumulative pan evaporation, while the drainage conditions were represented by the drained and undrained lysimeters. Another treatment, using good quality water for irrigation, represented the potential yield of the crop. The growth parameters, as well as the yield, showed an improvement with larger irrigation depth increments in the drained lysimeters. But, in contrast, in the undrained lysimeters, the yield was reduced with larger irrigation depth increments, mainly due to a sharp rise in water table depth during the irrigation cycles. The rise and fall in water table showed a high sensitivity and were also highly disproportionate to the irrigation and evapotranspiration events. The yield tended to be higher with a smaller depth of water applied more frequently in the undrained lysimeters. But, in view of the limitations of conventional surface irrigation to apply water in smaller depth increments, an improved drainage is imperative for cropping in shallow saline water table conditions. 相似文献