Day and night wind drift and evaporation losses in sprinkler solid-sets and moving laterals

Wind drift and evaporation losses (WDEL) represent a relevant water sink in sprinkler irrigation, particularly in areas with strong winds and high evaporative demand. The objectives of this paper include: (1) characterize WDEL under day and night operation conditions for solid-set and moving lateral configurations; (2) propose adequate predictive equations; and (3) prospect the effect of sprinkler irrigation on the meteorological variables and on the estimates of reference evapotranspiration. A total of 89 catch can irrigation evaluations were performed in both irrigation systems and under day and night conditions. Different predictive equations of WDEL were proposed for combinations of the two irrigation systems and the two operation times. The equations were selected based on their capability to explain and predict WDEL. Most equations use wind speed alone as an independent variable, although some use relative humidity or combinations of both variables plus air temperature. In the semi-arid meteorological conditions of Zaragoza (Spain), the average WDEL for the solid-set were 15.4 and 8.5% during day and night irrigations, respectively. For the experimental moving lateral, losses amounted to 9.8% during the day and 5.0% during the night. The effect of sprinkler irrigation on the meteorological variables was moderate, with small increases in relative humidity (3.9%) and decreases in air temperature (0.5 °C) during the irrigation event and a few minutes afterwards. Consequently, reference evapotranspiration, estimated by the Penman-Monteith method, decreased during the irrigation event by 0.023 mm h⁻¹ on the average. This decrease represents 2.1% of WDEL, suggesting that the WDEL do not significantly contribute to satisfy crop water requirements, and therefore constitute a consumptive water loss.     

From on-farm solid-set sprinkler irrigation design to collective irrigation network design in windy areas

In this paper, a contribution to the design of collective pressurised irrigation networks in solid-set sprinkler-irrigated windy areas is presented. The methodology is based on guaranteeing minimum on-farm performance, using a historical hourly wind speed database and a ballistic solid-set irrigation simulation model. The proposed method was applied to the Montesnegros Irrigation District (central Ebro basin, Spain). The district irrigates an area of 3493 ha using an on-demand schedule. The average wind speed in the area is 2.8 m s⁻¹. An analysis of district water records showed that farmers often reduce water demand when the wind speed is high, but their irrigation decision making is limited by the capacity of the irrigation network and by the unpredictable character of local winds. Simulations were performed for 11 irrigation seasons, 2 triangular sprinkler spacings (18 m × 18 m and 18 m × 15 m), and 2 sprinkler models. The percentage of monthly suitable time for irrigation was determined for four management strategies. The first one was based on a wind speed threshold (3 m s⁻¹), while the other three were based on three levels (standard, relaxed and restrictive) of two irrigation performance parameters: the Christiansen Uniformity Coefficient (CU) and the Wind Drift and Evaporation Losses (WDEL). The standard strategy classified the time as suitable for irrigation when CU ≥ 84% and WDEL ≤ 20%. The thresholds limits of the irrigation parameters for the relaxed strategy were CU ≥ 80% and WDEL ≤ 25%. Finally, the restrictive strategy used thresholds of CU ≥ 90% and WDEL ≤ 15%. The suitable time for the first strategy (56%) was always lower than for the standard and the relaxed strategies (with respective average values of 75 and 86%), and higher than for the restrictive strategy (30%). In order to design the collective network, the hydrant operating time was equalled to the suitable time for irrigation. The differences in the cost of the collective network plus the on-farm equipment were particularly relevant between the restrictive strategy and the other three. Differences in suitable operating time were clear between sprinkler spacings, and less evident between sprinkler models. The application of the proposed methodology may be limited by the availability of historical wind speed records and CU estimates for different combinations of sprinkler models, sprinkler spacings and wind speed.     

基于弹道理论有风条件下折射式喷头喷灌均匀度研究

为计算有风条件下折射式喷头水量分布及喷灌均匀度,以弹道轨迹理论为基础,依据风速分布模型,建立有风条件下折射式单喷头水量分布计算方法,采用该方法模拟出有风条件下Nelson D3000型喷头倒挂安装方式下水量分布特性,通过与实测资料进行对比,验证了模拟具有较高的准确度,可应用于有风条件下折射式喷头水量分布计算。在此基础上,选用4.76 mm(24号)喷嘴直径,模拟出不工况下单喷头水量分布,计算出组合情况下喷灌均匀度,分析了风速、风向、喷头间距、工作压力和安装高度5种因素对喷灌均匀度的影响,并对蒸发漂移损失进行了分析。结果表明:95%的置信区间下,喷头布置间距对喷灌均匀度的影响最显著,其次是安装高度和喷头工作压力,风速和风向对喷灌均匀度影响不显著。风速、喷头工作压力和安装高度都会对蒸发漂移损失产生影响,其中工作压力影响最大。当选用Nelson D3000型喷头在风速小于6 m/s的环境下喷灌时,应将喷头安装间距固定在2.13~3.04 m范围内。另外,该安装间距范围内,喷头安装高度和喷灌压力增大后,喷灌均匀度增大的效果不明显,因此应采用低压喷灌以降低喷灌系统运行成本;考虑到较高的喷头安装高度会产生较大的蒸发漂移损失,喷灌时还应适当降低喷头安装高度,以提高喷灌水分利用率。     

Sprinkler evaporation losses in alfalfa during solid-set sprinkler irrigation in semiarid areas

Gross sprinkler evaporation losses (SEL_g) can be large and decrease irrigation application efficiency. However, it is not universally established how much of the SEL_g contributes to decrease the crop evapotranspiration during the sprinkler irrigation and how much are the net sprinkler losses (SEL_n). The components of SEL were the wind drift and evaporation losses (WDEL) and the water intercepted by the crop (IL). The gross WDEL (WDEL_g) and evapotranspiration (ET) were measured simultaneously in two alfalfa (Medicago sativa L.) plots, one being irrigated (moist, MT) and the other one not being irrigated (dry, DT). Catch can measurements, mass gains, and losses in the lysimeters and micrometeorological measurements were performed to establish net WDEL (WDEL_n) during the irrigation and net IL (IL_n) after the irrigation as the difference between ET_MT and ET_DT. Also, equations to estimate IL_n and net sprinkler evaporation losses (SEL_n) were developed. IL_n was strongly related to vapor pressure deficit (VPD). SEL_n were 8.3 % of the total applied water. During daytime irrigations, SEL_n was 9.8 % of the irrigation water and slightly less than WDEL_g (10.9 %). During nighttime irrigations, SEL_n were slightly greater than WDEL_g (5.4 and 3.7 %, respectively). SEL_n was mainly a function of wind speed.     

Solid-set sprinklers irrigation of field boundaries: experiments and modeling

Numerous studies have analyzed the solid-set sprinkler irrigation system performance. However, the effect of field-boundaries irrigation has not been considered in the whole-field performance. The objectives of this study were (1) to characterize two different solutions to irrigate field boundaries (full-circle sprinkler equipped with a deflecting plate, DP, and partial-circle sprinklers, PC); (2) to calibrate and validate a ballistic model to adequately simulate these solutions; and (3) to analyze the two different designs (DP or PC) from a whole-field perspective. Two types of experiments were designed. The first was carried out with an isolated sprinkler under no windy conditions to estimate drop size distribution parameters. The second was performed in a solid-set sprinkler layout under windy conditions to calibrate and validate the ballistic model. The experimental design allows the comparison of both solutions under equal technical and meteorological conditions. Comparisons between designs (DP or PC) were established for a whole-field area in terms of irrigation performance and crop yield. From a technical point of view, PC sprinklers perform better than DP sprinklers. From an economical point of view, the shape and orientation of the plot and the legal requirements of the irrigation system design (minimum distance of the sprinkler line to the border) have an important effect on the optimal solution to irrigate field boundaries.     

Irrigation modernization and water conservation in Spain: The case of Riegos del Alto Aragón

This study analyzes the effects of irrigation modernization on water conservation, using the Riegos del Alto Aragón (RAA) irrigation project (NE Spain, 123354 ha) as a case study. A conceptual approach, based on water accounting and water productivity, has been used. Traditional surface irrigation systems and modern sprinkler systems currently occupy 73% and 27% of the irrigated area, respectively. Virtually all the irrigated area is devoted to field crops. Nowadays, farmers are investing on irrigation modernization by switching from surface to sprinkler irrigation because of the lack of labour and the reduction of net incomes as a consequence of reduction in European subsidies, among other factors. At the RAA project, modern sprinkler systems present higher crop yields and more intense cropping patterns than traditional surface irrigation systems. Crop evapotranspiration and non-beneficial evapotranspiration (mainly wind drift and evaporation loses, WDEL) per unit area are higher in sprinkler irrigated than in surface irrigated areas. Our results indicate that irrigation modernization will increase water depletion and water use. Farmers will achieve higher productivity and better working conditions. Likewise, the expected decreases in RAA irrigation return flows will lead to improvements in the quality of the receiving water bodies. However, water productivity computed over water depletion will not vary with irrigation modernization due to the typical linear relationship between yield and evapotranspiration and to the effect of WDEL on the regional water balance. Future variations in crop and energy prices might change the conclusions on economic productivity.     

Computer evaluation of sprinkler irrigation uniformity

Summary A method for evaluating the water application rate (WAR) and uniformity coefficient (Cu) of overlapping irrigation sprinklers is given for realistic field conditions which includes wind drift of the sprinkler spray. The method requires as input — the geometry of the sprinkler arrangement, trajectories of water drops from the sprinkler nozzle as calculated by the equations of motion and the WAR distribution (discharge) profile of a single sprinkler experimentally observed under windless conditions. Wind direction with respect to the main sprinkler line is shown to have a small effect on Cu and is assumed to be parallel to the main line. Results show that the effect of wind drift of sprinkler spray on Cu can be neglected for wind velocities less than 1 ms^–1 (Fig. 8). Analysis of simulated discharge profiles (Table 1) shows that the maximum value of the uniformity coefficient was obtained with triangular sprinkler discharge profiles at low values of spacing, changing to trapezoidal profiles as the spacing increases (Figs. 8 and 9). The effect of nozzle pressure on WAR was evaluated for the pressure range between 294 and 490 kPa and an optimum layout of overlapping sprinklers, designed to minimize the effect of wind drift and nozzle pressure on the uniformity of WAR distribution, is presented.Notation C _D air drag coefficient of water drop - Cu uniformity coefficient - D diameter of water drop - d _k reference k-th water drop - incremental scanning distance at a certain size matrix - g acceleration of gravity - h _pm mean value of water application rate (mean value of WAR) - h (x, y) WAR at points P (x, y) - h _o (k, n) WAR at points P _o (k, n) - h _p (l, m) WAR at cross points of a certain size matrix covering the unit area for calculation of Cu - i row index number (see Fig. 3) - j column index number (see Fig. 3) - K Kàrmán's constant - k index number of water drop, d _k - L number of scanning points along main line - l index number of scanning point along main line - M number of scanning points along the line perpendicular to main line - m index number of scanning point along the line perpendicular to main line     

Response of alfalfa (<Emphasis Type="Italic">Medicago sativa</Emphasis> L.) to diurnal and nocturnal saline sprinkler irrigations. I: total dry matter and hay quality

Little information is available on the quantitative effects on crops of saline sprinkler irrigations and the presumable beneficial effects of nocturnal versus diurnal irrigations. We measured crude protein content, carbon isotope discrimination and total dry matter (TDM) of alfalfa (Medicago sativa L.) subject to diurnal and nocturnal saline sprinkler irrigations. The work was carried out in Zaragoza (Spain) during the 2004–2006 growing seasons with a triple line source sprinkler system using synthetic saline waters dominated by NaCl with an irrigation water EC ranging from 0.5 to 5.6 dS m⁻¹. The quality of alfalfa hay assessed through its crude protein concentration was not significantly affected by salinity. Carbon isotope discrimination, an indicator of the effect of osmotic stress on plant water status, tended to decrease with increases in salinity. Based on a piecewise linear response model, alfalfa grown under saline sprinkler irrigation was shown to be more tolerant (threshold soil salinity, EC_e = 3.5 dS m⁻¹) than in previous experiments under surface irrigation (threshold EC_e = 2.0 dS m⁻¹) at relatively low salinity values, but became more sensitive at higher salinity values as shown by the higher absolute slope (13.4%) for sprinkler as compared to surface irrigation (7.3%). No significant differences in TDM were found between diurnal and nocturnal saline sprinkler irrigations. The recommended practice of irrigating at night for sprinkler irrigation using saline water is therefore not supported by our results in alfalfa grown under semiarid conditions.     

Combined effect of technical, meteorological and agronomical factors on solid-set sprinkler irrigation: I. Irrigation performance and soil water recharge in alfalfa and maize

In this work, maize (Zea mays L.) and alfalfa (Medicago sativa L.) were irrigated in two adjoining plots with the same sprinkler solid-set system. Irrigation was evaluated between four sprinklers in the central position within each plot, above the canopy with pluviometers and in the soil with a FDR probe. Maize and alfalfa were simultaneously irrigated under the same operational and technical conditions during two seasons: in 2005, the solid-set irrigation system layout was rectangular, 15 m between sprinklers along the irrigation line and 15 m among lines (R15 × 15), and the seasonal irrigation applied according to the crop evapotranspiration (ET_c); in 2006, the solid-set layout was R18 × 15 and the seasonal irrigation was around 30% lower than the ET_c. The irrigation depth above the canopies (ID_C) and the soil water recharge after irrigation (RW) were monitored using a 3 m × 3 m grid (25 points in 2005 and in 30 points in 2006). For maize, RW was assessed both in the lines of plants (CL) and between the lines (BCL).The average values of ID_C were similar between crops during both seasons but the uniformity (CUC) of the ID_C noticeably depended on the crop: the differences were greater between crops than between sprinklers spacings (R15 × 15 and R18 × 15). The CUC of ID_C, the RW and the CUC of RW were greater for alfalfa than for maize. The CUC of ID_C was greater than the CUC of RW for both crops. The RW was significantly related with the ID_C throughout the irrigation season for alfalfa. The correlation was weaker for maize, with important differences between positions and between growth stages. At the beginning of the season, the RW significantly correlated with the ID_C, both in the CL and BCL positions. However, the correlation weakened when the maize grew, especially in the CL, because the maize plants redistributed the water.The results show that the height and canopy architecture of the crop must be considered in the analysis of the sprinkler water distribution as factors influencing the irrigation performance.     

Combined effect of technical, meteorological and agronomical factors on solid-set sprinkler irrigation: II. Modifications of the wind velocity and of the water interception plane by the crop canopy

Maize (Zea mays L.) and alfalfa (Medicago sativa L.) were simultaneously irrigated in two adjoining plots with the same sprinkler solid-set system under the same operational and technical conditions. The Christiansen's uniformity coefficient (CUC) and the wind drift and evaporation losses (WDEL) were assessed from the irrigation depth (ID_C) collected into pluviometers above each crop. A network of pluviometers was located above the maize canopy. Two networks of pluviometers were located above the alfalfa, one above the canopy and the other at the same level as that above the maize. The latter was used to analyze the effects of the water collecting plane. The wind velocity (WV) profile was measured above each crop using anemometers located at three levels. Both the CUC and the WDEL differed between maize and alfalfa.The crops modified both the wind velocity above the canopy and the water interception plane. Both effects were related to the height of the crops (h).When h increased, the water interception plane increased, and the overlap of the sprinklers decreased. The CUC of the ID_C increased with the overlap. Because h was greater for maize than for alfalfa, the CUC was noticeably smaller for maize.The WV greatly decreased in proximity to the canopy. The WV at the level of the nozzles was smaller above the maize because the top of the canopy was closer to the nozzles than it was for alfalfa. However, the CUC of the ID_C mainly depended on the WV at higher levels, where the WV was similar above both maize and alfalfa. The logarithmic wind profile overestimated the vertical variation of the WV in the space where the sprinklers distributed the water.The WDEL was greater above the maize than above the alfalfa. This finding was related to the underestimation of the ID_C above maize, especially under windy conditions, because the pluviometers were located very close to the nozzles.     

Wind effects on solid set sprinkler irrigation depth and yield of maize (<Emphasis Type="Italic">Zea mays</Emphasis>)

A field experiment was performed to study the effect of the space and time variability of water application on maize (Zea mays) yield when irrigated by a solid set sprinkler system. A solid set sprinkler irrigation layout, typical of the new irrigation developments in the Ebro basin of Spain, was considered. Analyses were performed (1) to study the variability of the water application depth in each irrigation event and in the seasonal irrigation and (2) to relate the spatial variability in crop yield to the variability of the applied irrigation and to the soil physical properties. The results of this research showed that a significant part of the variability in the Christiansen coefficient of uniformity (CU), and wind drift and evaporation losses were explained by the wind speed alone. Seasonal irrigation uniformity (CU of 88%) was higher than the average uniformity of the individual irrigation events (CU of 80%). The uniformity of soil water recharge was lower than the irrigation uniformity, and the relationship between both variables was statistically significant. Results indicated that grain yield variability was partly dictated by the water deficit resulting from the non-uniformity of water distribution during the crop season. The spatial variability of irrigation water depth when the wind speed was higher than 2 m s^–1 was correlated with the spatial variability of grain yield, indicating that a proper selection of the wind conditions is required in order to attain high yield in sprinkler-irrigated maize.     

Seasonal on-farm irrigation performance in the Ebro basin (Spain): Crops and irrigation systems

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 (IR_n) 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.     

变量喷洒全射流喷头副喷嘴优化与评价

为解决全射流喷头实现变量喷洒时由于压力变化而产生的水量分布不均匀问题,以20PXH型变量喷洒全射流喷头为研究对象,设计不同副喷嘴改善水量分布。通过射流理论分析设计了8种副喷嘴方案,测量了喷头径向水量分布,采用不同压力下喷灌强度差值分析的方法,得到方案5挡板式副喷嘴结构改善水量情况最好。通过测量不同挡板角度及不同压力下水量分布,以均匀性系数值最大为目标,以挡板角度及均匀性取值范围为约束条件,首次建立了变量喷洒全射流喷头喷洒均匀性的综合评价函数,并求导得到最佳挡板角度为21.2°。     

Effect of nozzle type on runoff and yield of corn and sorghum under center pivot sprinkler systems

Summary Corn (Zea mays L.) and grain sorghum (Sorghum bicolor L.) production were compared under impact and spray nozzled center pivot sprinkler systems. The crops were grown under two pairs of sprinkler systems located approximately 110 km apart. One system of each pair was equipped with high pressure (379 or 414 kPa) impact sprinkler heads and the other system was equipped with low pressure (172 or 207 kPa) spray nozzles. Half of each circle was planted to corn and half was planted to sorghum. Additionally, four tillage treatments were included in the experimental design (conventional tillage, conventional tillage + deep ripping, conventional tillage + diking, and minimum tillage). The evaporative losses from the high pressure system with impact sprinkler heads were not significantly different from the low pressure system with spray nozzles. The minimum tillage and deep ripped treatments reduced runoff while diking eliminated it. The two nozzle types did not produce significantly different grain sorghum yields; however, corn yielded significantly more under the high pressure system with impact sprinkler heads than under the low pressure system with spray nozzles. The different tillage treatments did not influence yields of either crop significantly.Contribution of the Texas Agricultural Experiment Station. Paper No. 19198     

Influence of plant traits on production costs and profitability of strawberry in southeast Queensland

In Queensland the subtropical strawberry (Fragaria × ananassa) breeding program aims to combine traits into novel genotypes that increase production efficiency. The contribution of individual plant traits to cost and income under subtropical Queensland conditions was investigated, with the overall goal of improving the profitability of the industry through the release of new strawberry cultivars. The study involved specifying the production and marketing system using three cultivars of strawberry that are currently widely grown annually in southeast Queensland, developing methods to assess the economic impact of changes to the system, and identifying plant traits that influence outcomes from the system.From May through September P (price; $ punnet⁻¹), V (monthly mass; tonne of fruit on the market) and M (calendar month; i.e. May = 5) were found to be related (r² = 0.92) by the function (±SE) P = 4.741(±0.469) − 0.001630(±0.0005)V − 0.226(±0.102)M using data from 2006 to 2010 for the Brisbane central market. Both income and cost elements in the gross margin were subject to sensitivity analysis.‘Harvesting’ and ‘Handling/Packing’ ‘Groups’ of ‘Activities’ were the major contributors to variable costs (each >20%) in the gross margin analysis. Within the ‘Harvesting Group’, the ‘Picking Activity’ contributed most (>80%) with the trait ‘display of fruit’ having the greatest (33%) influence on the cost of the ‘Picking Activity’. Within the ‘Handling/Packing Group’, the ‘Packing Activity’ contributed 50% of costs with the traits ‘fruit shape’, ‘fruit size variation’ and ‘resistance to bruising’ having the greatest (12-62%) influence on the cost of the ‘Packing Activity’. Non-plant items (e.g. carton purchases) made up the other 50% of the costs within the ‘Handling/Packing Group’. When any of the individual traits in the ‘Harvesting’ and ‘Handling/Packing’ groups were changed by one unit (on a 1-9 scale) the gross margin changed by up to 1%. Increasing yield increased the gross margin to a maximum (15% above present) at 1320 g plant⁻¹ (94% above present). A 10% redistribution of total yield from September to May increased the gross margin by 23%. Increasing fruit size increased gross margin: a 75% increase in fruit size (to ≈30 g) produced a 22% increase in the gross margin.The modified gross margin analysis developed in this study allowed simultaneous estimation of the gross margin for the producer and gross value of the industry. These parameters sometimes move in opposite directions.     

Comparisons of two soil water flow models under variable irrigation

Performance of WATCOM (a numerical model) and CRPSM (a simple water balance model) were assessed in simulating root zone water storage and water balance components under cowpea in Nigeria using a line source sprinkler system. Three sets of field data were collected: the first was used for calibration and model parameters’ estimation and the other two for testing and comparisons. The simulated soil water storage and crop evapotranspiration with WATCOM and CRPSM were in good agreement with field-measured data though WATCOM performed significantly better (P < 0.05) under the stressed condition. The maximum average error between predicted and measured soil water storage was −0.95 and +1.47 mm for WATCOM and CRPSM, respectively, while that between measured and predicted actual crop evapotranspiration was +2.7 and +11.38 mm, respectively, for the two models. WATCOM gave generally higher cumulative deep percolation and lower evapotranspiration than that of CRPSM for all irrigation levels (P < 0.05), and values of deep percolation for WATCOM were in better agreement with field data than that of CRPSM. This suggests that drainage below the field capacity needs to be included in CRPSM and that WATCOM will be a more useful management tool when detailed soil parameter is required and under variable water regime.     

Comparison of drip and sprinkler irrigation strategies on sunflower seed and oil yield and quality under Mediterranean climatic conditions

This study compares the effects of different irrigation regimes on seed yield and oil yield quality and water productivity of sprinkler and drip irrigated sunflower (Helianthus annus L.) on silty-clay-loam soils in 2006 and 2007 in the Mediterranean region of Turkey. In sprinkler irrigation a line-source system was used in order to create gradually varying irrigation levels. Irrigation regimes consisted of full irrigation (I₁) and three deficit irrigation treatments (I₂, I₃ and I₄), and rain-fed treatment (I₅). In the drip system, irrigation regimes included full irrigation (FI-100), three deficit irrigation treatments (DI-25, DI-50, DI-75), partial root zone drying (PRD-50) and rain-fed treatment (RF). Irrigations were scheduled at weekly intervals both in sprinkler and drip irrigation, based on soil water depletion within a 0.90 m root zone in FI-100 and I₁ plots. Irrigation treatments influenced significantly (P < 0.01) sunflower seed and oil yields, and oil quality both with sprinkler and drip systems. Seed yields decreased with increasing water stress levels under drip and sprinkler irrigation in both experimental years. Seed yield response to irrigation varied considerably due to differences in soil water contents and spring rainfall distribution in the experimental years. Although PRD-50 received about 36% less irrigation water as compared to FI-100, sunflower yield was reduced by an average of 15%. PRD-50 produced greater seed and oil yields than DI-50 in the drip irrigation system. Yield reduction was mainly due to less number of seeds per head and lower seed mass. Soil water deficits significantly reduced crop evapotranspiration (ET), which mainly depends on irrigation amounts. Significant linear relationships (R² = 0.96) between ET and oil yield (Y) were obtained in each season. The seed yield response factors (ky_seed) were 1.24 and 0.86 for the sprinkler and 1.19 and 1.06 for the drip system in 2006 and 2007, respectively. The oil yield response factor (ky_oil) for sunflower was found to be 1.08 and 1.49 for both growing seasons for the sprinkler and 1.36 and 1.25 for the drip systems, respectively. Oil content decreased with decreasing irrigation amount. Consistently greater values of oil content were obtained from the full irrigation treatment plots. The saturated (palmitic and stearic acid) and unsaturated (oleic and linoleic acid) fatty acid contents were significantly affected by water stress. Water stress caused an increase in oleic acid with a decrease in linoleic acid contents. The palmitic and stearic acid concentrations decreased under drought conditions. Water productivity (WP) values were significantly affected by irrigation amounts and ranged from 0.40 to 0.71 kg m⁻³ in 2006, and from 0.69 to 0.91 kg m⁻³ in 2007. The PRD-50 treatment resulted in the greatest WP (1.0 kg m⁻³) and irrigation water productivity (IWP) (1.4 kg m⁻³) in both growing seasons. The results revealed that under water scarcity situation, PRD-50 in drip and I₂ in sprinkler system provide acceptable irrigation strategies to increase sunflower yield and quality.     

Soil management and traffic effects on infiltration of irrigation water applied using sprinklers

Zero tillage and controlled traffic have been proposed as means for more productive and sustainable irrigated farming. Both practices affect soil infiltration characteristics and, therefore, should have effects on sprinkler irrigation performance. This study compared water infiltration and runoff in three sprinkler irrigation tests performed on an alluvial loam soil at different times during a maize (Zea mays L.)–cotton (Gossypium hirstium L.) rotation under two soil managements: permanent beds with crop residue retention (PB: planting beds maintained unaltered from year to year) and conventional beds with residues incorporated with tillage (CB: disc and chisel ploughing followed by rotavator pass and bed forming every year). Traffic was controlled and two types of furrows were distinguished in both tillage systems: with (+T) and without (−T) wheel traffic. The irrigation tests were performed on maize at full cover, on bare soil just before cotton sowing and on cotton with 50% ground cover. Infiltration and runoff were affected notably by both traffic and soil management. The soil under PB infiltrated more water than under CB, and −T furrows more than +T furrows. Considering the combined treatments, −T furrows in the CB system infiltrated more water than +T furrows in the PB system. A sprinkler irrigation model for simulating water application and soil infiltration and runoff was formulated. The model was used to analyse irrigation performance under infiltration characteristic of the CB and PB systems in trafficked and non-trafficked furrows. Five irrigation performance indicators were used to assess the various combinations of tillage and traffic: Wilkox–Swailes coefficient of uniformity; application efficiency; deep percolation ratio; tail water ratio; and adequacy. The model was used to develop operation diagrams and provided guidelines for making irrigation decisions in the new controlled traffic/permanent bed system and in a standard conventional system.     

Characterizing pivot sprinklers using an experimental irrigation machine

In this work, a Fixed Spray Plate Sprinkler (FSPS) and two Rotating Spray Plate Sprinklers (RSPS) were compared in terms of wetted diameter, wind drift and evaporation losses (WDEL), static water precipitation pattern and dynamic water application profile. An experimental irrigation machine reproducing a pivot section was constructed and used to perform experiments in static and dynamic (linear displacement) modes. Water application from FSPS often resulted in a bi-modal pattern, while RSPS produced bell-shaped or triangular patterns. At a nozzle elevation of 2.4 m and an operating pressure of 140 kPa the wetted diameter was 1.6 m larger for the RSPS than for the FSPS. The differences between the two RSPS amounted to 0.5 m on the average. Reducing the nozzle elevation from 2.4 to 1.0 m resulted in a 2.6 m decrease in the wetted diameter. The use of RSPS may result in reduced surface runoff losses, due to the increased wetted diameter and the reduced peak precipitation rate. WDEL for RSPS were statistically related to wind speed, although no significant differences were found between both types of RSPS or between the two nozzle elevations. According to the experimental results, reducing the nozzle elevation will not result in reduced WDEL, but will increase the chances for runoff.     

Can shelterbelts improve sprinkler irrigation performance under windy semi arid conditions?

Field experiments were performed to study the effect that wind shelterbelts has on irrigation uniformity of hand move sprinkler irrigation system located in northwest Kenya. Catch can tests were performed to evaluate the distribution of applied water using coefficient of uniformity and distribution uniformity for plots with shelterbelt and without shelterbelt scenarios. Three medium pressure twin nozzle sprinkler head types were tested to determine their water distribution uniformity at varying wind speed and working pressure and obtained results were statistically analysed. The analysis was used to ascertain the performance of the medium pressure sprinklers under varying wind conditions for the two scenarios. Results indicate that uniformity is improved by wind for wind speeds below 1.4?m/s. Analysis of data from sheltered and unsheltered plots showed a significant difference of uniformity parameters on sheltering with coefficient of uniformity for sheltered plots averaging 84?% compared to 74?% for unsheltered plots. Results indicate that the coefficient of uniformity values were higher than the distribution uniformity values although both had a strong linear relationship with a coefficient of determination above 0.96 in both scenarios. It is concluded that shelterbelts improve sprinkler irrigation performance under windy conditions.