Response of tall fescue to irrigation water salinity,leaching fraction,and irrigation frequency

A long-term study in the rhizotron at the U.S. Salinity Laboratory established the yield and evapotranspiration of tall fescue as a function of irrigation water salinity, leaching fraction, and irrigation frequency. As the salt concentration of the irrigation water increased or leaching fraction decreased, dry matter production was reduced significantly. Differences in production because of irrigation frequency, however, were insignificant. With low stress (high leaching, L = 0.27, and low salinity water, S = 1 dS/m) annual dry matter yields were 2.0 kg/m², compared to annual yields of 1.4 kg/m² with high stress (low leaching, L = 0.09, and high salinity water, S = 4 dS/m).Annual evapotranspiration dropped from 1860 mm for low stress treatments to 1170 mm for high stress. Soil evaporation was negligible for the mature grass stand. In concurrence with several models, relative dry matter production was proportional to relative water use.The salt tolerance of treatments dominated by osmotic potential was in agreement with that published for tall fescue. As matric potential decreased among treatments yields fell significantly below that predicted by the salt tolerance model.     

灌水量及灌水频率对玉米生长和水分利用的影响

利用遮雨棚蒸渗桶栽试验,研究灌水量和灌水频率对夏玉米生长、产量和水分利用的影响.试验以“郑单958”为研究材料,设置3个灌水量水平W1(120%ETc),W2(100%ETc)和W3(80%ETc)和3个灌水频率D1(3 d),D2(6 d)和D3(9 d)共9个处理,在生育期内对桶栽玉米的各项生长指标进行观测,分析不同处理对玉米的影响.结果表明:玉米的株高、叶面积、干物质量和产量随着灌水量的增大,均呈现出增加趋势;随着灌水频率的增大,均呈现出下降趋势.显著性分析表明,灌水量对夏玉米生长特性和产量的影响程度大于灌水频率.单株玉米产量在W₁D3处理下达到最大值,在W₃D1处理下玉米产量最小,差异具有统计学意义.水分利用效率和灌溉水利用效率则随灌水量的增大呈现先增大后减小趋势,且随灌水频率的增加逐渐降低.W₂D3处理的水分利用效率和灌溉水利用率最高,分别为1.83和1.61 kg/m3.基于各处理水分利用效率和产量变化,W₁D3(120%ETc,9 d)可作为基于试验条件下较适宜的灌水技术.     

绿洲灌区膜下滴灌调亏对辣椒品质及产量的影响

为揭示滴灌水分亏缺对辣椒营养品质及产量的影响,以"陇椒6号"为对象,在辣椒苗期分别施加轻度(65％～75％田间持水量)、中度(55％～65％田间持水量)和重度水分调亏(45％～55％田间持水量),在盛果期和后果期分别施加轻度水分亏缺,以全生育期充分供水(75％～85％田间持水量)为对照,分别测定各水分处理辣椒青果营养品...     

Effects of timing and duration of brackish irrigation water on fruit yield and quality of late summer melons

Brackish water (7 dS m⁻¹) is frequently utilized to drip-irrigate crops in the Negev desert of Israel, the practice being to use deep sandy soils (96% sand) to avoid soil salinization. When muskmelon (Cucumis melo L.), a moderately salt-sensitive crop species, was grown using brackish irrigation under these conditions, yields declined due to a significant reduction in fruit size, but fruit quality parameters improved markedly. In the present study, we tested the hypothesis that the use of fresh irrigation water during the early vegetative phase would increase canopy size and leaf area index (LAI) and hence the potential productivity of the melon plant. The application of brackish water during the reproductive phase, on the other hand, would improve fruit quality. Using multiple irrigations within a 24-h period, applied with drip irrigation, we examined the timing, the duration, and the concentration of brackish irrigation water as tools to optimize fruit yield and quality in late-summer melons. Indeed, the combination of fresh (1.2 dS m⁻¹) and brackish (7 dS m⁻¹) irrigation water increased the yield level to that of fresh water plants whereas it brought about the improvement of fruit quality typical to brackish water plants, thus providing an attractive approach to optimize late-summer melon production. Our results demonstrate the trade-off between fruit size and fruit quality as related to the timing and the duration of brackish irrigation water. The use of a milder (<4.5 dS m⁻¹) salinity level of irrigation water from plant emergence until harvest may be considered as well.     

Amelioration of salt stress by irrigation management in pepper plants grown in coconut coir dust

A long-term greenhouse experiment was conducted to study the effects of irrigation frequency and salinity on pepper fruit yield and quality in crops growing in coconut coir. Two salinity levels (4 mM NaCl, 2.6 dS m⁻¹ and 24 mM NaCl, 4.6 dS m⁻¹) were combined with four irrigation treatments (one irrigation event every two days (0.5), one irrigation event per day (1), four irrigation events per day (4), and eight irrigation events per day (8)) in a 2 × 4 factorial combination. The effect on fruit quality was evaluated at the early and late harvest seasons, corresponding with two different periods of fruit production (May and July). We found that above-ground total biomass and marketable fruit yield decreased in the salinized treatments. When salinized (24 mM NaCl) nutrient solution (NS) was applied, increasing the number of irrigation events to eight per day resulted in a decrease in the incidence of blossom-end rot and a corresponding increase in the marketable fruit yield. When control (4 mM NaCl) NS was applied, one irrigation event per day yielded as much marketable fruit as was produced with the highest irrigation frequency, and therefore increased water use efficiency, expressed as marketable fruit weight per L of NS applied. When NS containing 24 mM NaCl was used, there was an increase of Cl⁻ but not Na⁺ in the leaf tissue, with this increase reaching its maximum in the treatment involving eight irrigation events per day. Salinity decreased the Ca²⁺ concentration of the fruit only in the early harvest season of production. However, increasing irrigation frequency consistently resulted in higher Ca²⁺ concentration in the fruit. The effects of salinity on the morphological and organoleptic properties of the fruit were more pronounced in the late harvest season.     

Effects of irrigation method on chile pepper yield and Phytophthora root rot incidence

A field experiment was conducted in 1995 and 1996 to examine the effects of different irrigation methods on yields and Phytophthora root rot disease of chile plants (Capsicum annum New Mexico `6–4'). Three irrigation methods, daily drip, 3-day drip, and alternate row furrow irrigation, were applied to plots infested with P. capsici and uninfested plots. For both years, the drip irrigation (either daily or 3-day) created higher marketable green chile yields than the alternate row furrow irrigation (p < 0.05), and the yields between the daily and 3-day drip irrigation were statistically similar. The effect of irrigation on marketable combined yields was similar to that on green chile yields. In 1995, root rot disease incidence in the infested plots was significantly higher under alternate row furrow irrigation than for daily and 3-day drip irrigation. There was no disease development in the uninfested plots regardless of the irrigation method. The disease decreased green chile yield by 55% (p < 0.1), and combined yield (green + red chile) by 36% (p < 0.1) in 1995 compared to that in uninfested plots in alternate row furrow irrigation. In 1996, however, no disease occurred in any treatment. The results suggested that drip irrigation increases chile yield through providing either favorable soil moisture conditions or unfavorable conditions for Phytophthora propagation.     

营养液供液量与供液频率对冬春茬辣椒的影响

为了了解营养液不同供液量和供液频率对辣椒生长发育、果实品质和水分利用效率的影响,以“洋大帅”为试验材料,采用基质槽培的栽培方式进行试验.试验设置了3个不同供液量(在苗期,每株辣椒每天的供液量分别为W1:300 mL,W2:400 mL,W3:500 mL,开花坐果期每株辣椒每天的供液量加倍,结果期每天的供液量是苗期的3倍)和3个不同供液频率(整个生育期,每天的供液频率维持不变,即T1:2次/d,T2:3次/d,T3:4次/d).结果表明:当供液量为W2时,地上部分与地下部分相关性最好;处理W1T2水分利用效率最高,为18.13 kg/m³,但是其产量最低;处理W3T1的总根表面积最大,为754.54 cm³;处理W3T2辣椒生长最好,有最大的株高和茎粗,果实品质与水分利用效率也相对较好.因此,处理W3T2为试验条件下基质培冬春茬辣椒最佳的供液量和供液频率.     

Water and salt transport,water uptake,and leaf water potentials during regular and suspended high frequency irrigation of citrus

High frequency irrigation of citrus was interrupted for up to 2 months to study the dynamics of salt and water transport in soil, water uptake distributions and leaf water potentials. Irrigation water was applied to less than half the surface area per tree. Water content profiles and chloride distributions indicated that of the water uptake below the irrigated area, about 80% took place above 0.60-m depth, and that considerable water was taken up from outside the irrigated area. The water for the latter was supplied by lateral flow, as evidenced by the hydraulic gradients, the relative extent of the lateral flow in summer and winter, and the fact that at 0.90-m depth water contents were uniform. In summer, the citrus showed signs of stress after about 4 weeks of suspended irrigation. At that time leaf water potentials did not recover any longer during the night. This study indicates that high frequency irrigation of citrus is not too vulnerable to temporary system breakdown and that deficit-irrigation could be practiced.     

Effects of water quality and frequency of irrigation on growth and yield of barley (Hordeum vulgare L.)

A field trial on a loamy sand soil was carried out to study the effect of three irrigation waters with different qualities on growth and yield of ‘Gesto’, a barley (Hordeum vulgare L.) cultivar. Three irrigation water quality treatments (canal irrigation water, drainage water, and mixed canal and drainage waters at 1:1 ratio) were imposed with two irrigation frequencies (I and 2 week intervals). In addition, nitrogen and phosphorus fertilizers were applied at different rates. Barley grain and straw yields were significantly decreased under the use of drainage water (EC 10.7–16.7 dS m⁻¹), attributed mainly to reduction in the number of spikes per plant and grain weight. The mixed irrigation water (EC 6.8–9.9 dS m⁻¹) produced high seedling emergence and good vegetative growth, which was followed by high grain and straw yields. These yields were not significantly different from those under fresh canal irrigation water (EC 2.8–3.9 dS m⁻¹). Thus, mixed water could be another alternative for irrigation under similar experimental conditions especially with high rates of nitrogen (250–350 kg ha⁻¹) and phosphorus (90 kg ha⁻¹) fertilization at weekly irrigation intervals, which could eventually save more fresh irrigation canal water for other cultivated crops.     

Effects of irrigation water salinity and electrostatic water treatment for sugarcane production

Excess salinity in irrigation water reduces sugarcane yield and juice quality. This study was conducted to compare the effect of irrigation with water of 1.3 dS m⁻¹ vs. 3.4 dS m⁻¹ on sugarcane yield and quality, and to evaluate whether an electrostatic conditioning treatment of the water influenced the salt effects. The study was conducted in a commercial field divided into large plots ranging from 1.0 to 1.2 ha in size. Cane and sugar yields were reduced approximately 17% by the 3.4 dS m⁻¹ water compared to the 1.3 dS m⁻¹ water, but juice quality parameters were not affected. Conditioning of the irrigation water using a device called an ‘electrostatic precipitator’ which claimed to affect various water properties had no effect on cane yield, juice quality or soil salinity levels. The detrimental effect of the high salt irrigation water was somewhat less than might be expected, probably due to good late summer rainfall which may have flushed the root zone from the excessive salts.     

灌水周期和保水剂用法对小桐子水分利用的影响

为探明小桐子幼树水分高效利用管理模式,通过盆栽试验,研究了3种灌水周期(5,10,15 d)和3种保水剂用法(环施、半环施、穴施)对小桐子幼树生长和水分利用效率的影响.结果表明:灌水周期相同时,保水剂环施的水分利用效率最大,半环施的次之,穴施的最小;保水剂用法相同时,灌水周期为10 d的水分利用效率最大,5 d的次之,15 d的最小.保水剂环施时,与灌溉周期为5 d和15 d相比,灌溉周期为10 d能明显降低蒸散量,增加根区土壤含水量,同时显著促进植株生长,增加总干物质累积量分别为12.89%和51.83%,同时提高总水分利用效率分别为51.81%和58.28%.因此,在本试验条件下保水剂环施和灌水周期为10 d组合具有促进小桐子幼树生长和提高水分利用的作用.     

Effects of grapevine (Vitis vinifera L.) water status on water consumption, vegetative growth and grape quality: An irrigation scheduling application to achieve regulated deficit irrigation

Precision irrigation in grapevines could be achieved using physiologically based irrigation scheduling methods. This paper describes an investigation on the effects of three midday stem water potential (midday Ψ_S) thresholds, imposed from post-setting, over water use, vegetative growth, grape quality and yield of grapevines cv. Cabernet Sauvignon. An experiment was carried out on a vineyard located at the Isla de Maipo, Metropolitana Region, Chile, throughout the 2002/03, 2003/04 and 2004/05 growing seasons. Irrigation treatments consisted in reaching the following midday Ψ_S thresholds: −0.8 to −0.95 MPa (T1); −1.0 to −1.2 MPa (T2) and −1.25 to −1.4 MPa (T3) from post-setting to harvest. Results showed significant differences in grape quality components among treatments and seasons studied. In average, T3 produced smallest berry diameter (6% reduction compared to T1), high skin to pulp ratio (13% increment compared to T1) and significant increments in soluble solids and anthocyanins. Improvements in grape quality attributes were attributed to mild grapevine water stress due to significant reductions in water application (46% for T2 and 89% for T3 less in average, both compared to T1). This study found significant correlations between midday Ψ_S and berry quality components, no detrimental effects on yield by treatments were found in this study. This research proposes a suitable physiological index and thresholds to manage RDI and irrigation scheduling on grapevines to achieve high quality grapes on mild water stress conditions.     

Effects of deficit irrigation on yield, water productivity, and economic returns of wheat

A field experiment was conducted for 3 consecutive years to study the effects of water deficit on yield, water productivity and net return of wheat. Yield attributes were affected by deficit irrigation treatments although they are not statistically different in all cases. The grain and straw yields were significantly affected by treatments. The highest grain yield was obtained with the no-deficit treatment. Differences in grain and straw yield among the partial- (single- or two-stage deficit) and no-deficit treatments are small and statistically insignificant in most cases. The highest water productivity and productivity of irrigation water were obtained in the alternate deficit treatment (T₇), where deficits were imposed at maximum tillering (jointing to shooting) and flowering to soft dough stages of growth period, followed by single irrigation at crown root initiation stage. Under both land- and water-limiting conditions, the alternate deficit strategy (T₇) showed maximum net financial return. The results will be helpful in policy planning regarding irrigation management for maximizing net financial returns from limited land and water resources.     

Bell pepper response to surface and subsurface drip irrigation under different fertigation levels

A two-year field experiment was conducted in 2007 and 2008 to investigate different bell pepper responses to subsurface drip irrigation (SDI) and surface drip irrigation (DI) under four nitrogen levels: 0, 75, 150, and 300 kg/ha N (N₀, N₇₅, N₁₅₀, and N₃₀₀, respectively). Irrigation interval was set at 4 days. Bell pepper yield under SDI was significantly higher than that under DI by 4% in 2007 (13% in 2008). Water consumption under SDI was lower than that under DI by 6.7% in 2007 (7.3% in 2008). Meanwhile, root length density under SDI was obviously higher than that under DI by 11.8% in 2007 (12.5% in 2008). The percentage of root length below 10-cm soil depth under SDI was higher than that under DI by 7%, proving that SDI promotes crop root growth and enhances downward root development. Soil N residue under SDI was lesser than that under DI. Lastly, SDI with N application of 150 kg/ha is recommended as an optimal fertigation practice in improving bell pepper yield and water-use efficiency, as well as in NO₃ ⁻-N leaching.     

Yield and foliar injury responses of mature plum trees to salinity

Summary The salt tolerance of mature Santa Rosa plum trees was assessed on 20-year-old trees grown in the San Joaquin Valley of California. The experimental design consisted of six levels of irrigation water salinity (electrical conductivities of 0.3 to 8 dS/m) replicated five times with each replication consisting of ten trees. Salinity treatments imposed in March 1984 did not influence tree yields harvested in June 1984. In 1985, the second year of treatments, yield from the highest salt treatment (electrical conductivity of irrigation water, EC _i , of 8 dS/m) was reduced by half; the number of fruit harvested was reduced 40%, and fruit size was reduced significantly. Foliar damage was so severe by the end of 1985 that nonsaline water was applied to the two highest salt treatments (EC _i = 6 and 8 dS/m) in an attempt to restore tree vigor. In 1986 salt effects had become progressively worse on the continuing saline treatments. A linear piece-wise salt tolerance curve is presented for soil salinity values, expressed as the electrical conductivity of saturated extracts (EC _e ) integrated to a soil depth of 1.2 m over a 2-year period. The salt tolerance threshold for relative yield (Y _r ) based on 3 years of data was 2.6 dS/m and yield reduction at salinity levels beyond the threshold was 31% per dS/m (Y _ir=100 – 31 [EC _e – 2.6]j). Significant foliar damage occurred when leaf chloride concentrations surpassed 200 mmol/kg of leaf dry weight (0.7%). Sodium concentrations in the leaves remained below 10 mmol/kg (0.02%) until foliar damage became severe. This suggests that chloride was the dominant ion causing foliar damage.     

灌溉时段及水温对膜下滴灌棉花生长及产量的影响

为探究不同灌溉时段及水温对膜下滴灌棉花生理特性及产量的影响,设置4个灌溉水温梯度分别为15.00(正常灌溉水温),20.00,25.00,30.00℃,2个灌溉时段分别为日间、夜间(分别记为DW,NW)进行完全组合设计,共计8个处理.结果表明,增温灌溉提前了棉花生育进程,促进了棉花株高、茎粗、叶面积增长,有利于棉花光合作用的进行,且在夜间进行增温灌溉效果更显著.增温灌溉使棉花产量显著提高2.95%～14.13%,夜间灌溉较日间灌溉棉花产量平均提高3.34%.基于回归分析确定提高棉花产量的最佳灌溉时段为夜间,最佳灌溉水温为26.38℃,对应的产量为7 482.96 kg/hm².该研究可为北疆膜下滴灌棉花实施增温灌溉技术提供理论依据和技术参考.     

Optimization of furrow irrigation schedules,designs and net return to water

A seasonal furrow irrigation model consisting of irrigation scheduling and kinematic-wave-based hydraulic submodels was modified to incorporate an economic optimization submodel. The model used a systematic simulation technique to optimize furrow irrigation schedules and designs assuming 80% irrigation adequacy at cutoff time. The irrigation schedules and designs were optimized for the homogeneous and heterogeneous infiltration under the mean and observed ET_o (grass reference crop ET) conditions. The optimal management allowable depletion (MAD) level changed with the variation in ET_o condition, and with the consideration of spatial and temporal (seasonal) variability in infiltration characteristics. Irrigation design changed with both infiltration conditions and MAD level. Infiltration variability did not influence the bean yield. However, the return to water decreased when spatial variability in infiltration conditions was considered. Using mean ET_o resulted in slightly higher yield and net return to water as compared to using observed ET_o. A small variation in daily mean ET_o values with respect to daily observed ET_o values caused a change in both irrigation schedules and designs. Therefore, mean ET_o cannot be used to forecast irrigation schedules and designs at the beginning of crop season. The net return to water increased (1.7 to 3.6%), and the seasonal inflow, losses, and bean yield decreased in the case of variable interval scheduling (holding MAD constant) as compared to the fixed interval scheduling (MAD varies).     

Response of Salustiana oranges to high frequency deficit irrigation

Summary Mature Salustiana orange trees under drip irrigation were subjected to deficit irrigation during three years. The water applied (including effective rainfall) in the five irrigation treatments was: (A) 60% of the evaporation of a Class A pan over irrigated grass (Control treatment); B) and C 80% and 60% of control, during the whole year, respectively; (D) 60% of control during the flowering and fruit set period; (E) 60% of control during the fruit maturation period. During the rest of the year, treatments D and E received the same amount of water as the control. There were four replicates in a completely randomized block design. Irrigation frequency was the same for all treatments. Crop evapotranspiration (ET) was estimated by the water balance method using a neutron moisture meter. ET for the control treatment was about 840 mm/year and it was reduced in the deficit treatments. Irrigation treatments affected both yield and fruit quality although the effects varied between years according to the season's rainfall. Fruit number was not affected by the irrigation treatments, therefore differences in yield were due to effect on average fruit weight. Compared to the control treatment, treatments B and C decreased yield significantly (p = 0.05) by 5% and 15%, respectively, and increased the total soluble solids and acids content of the fruit juice. Water deficit in the flowering and fruit set period (treatment D) decreased yield by 4%, acids content of the juice and peel thickness. Treatment E produced fruit of lower quality with thicker peel and more acids than the control. Treatments did not affect juice and pulp content, maturity index of fruits nor maturation time. The effects of the irrigation treatments on the water status of the trees, fruit set and abscission and their implications on irrigation scheduling are also discussed.     

Social power,water control and irrigation systems

The principal finding of the study is that social power positions held by Egyptian farmers sharings a common watercourse do not have significant influence in the farmer's ability to control irrigation water distribution. Other variables used to describe irrigation management; location on the water course and farmers' use of more than one source of water to irrigate; also do not yield any explanations as to why particular farmers have more control over their irrigation than others. Farmers who have more control are less likely to be affected by other farmers' actions, physical problems on delivery canals, breakdown in pumps, and government officials actions. While differences in irrigation control among farmers exist, no single cause is identified. Two explanations for the findings are (1) water control is sufficient for a large percentage of Egyptian farmers, and (2) adequately explaining irrigation behavior cannot be done with separate variables.Deceased