Water Application Rates Research Articles

Effects of Water and Nitrogen Coupling on Growth, Yield and Quality of Greenhouse Tomato

Irrigation water is essential for greenhouse plants because it is the only water source in the greenhouse. In addition, escalating water costs and expensive fertilizers have raised concerns about adopting advanced technology to improve water and nitrogen utilization efficiency. This study aimed to explore the effects of different water and nitrogen application rates on yield, fruit quality, and water and nitrogen utilization efficiency in southeast China. Plants were irrigated every 7–10 days at different proportions of crop evapotranspiration (ETc) based on the modified Penman–Monteith formula (ET0). The crop coefficient (Kc) was adopted as 0.6, 1.15, 1.15 and 0.9 during the seedling stage, flower stage, the mid-season stage and the end of the season stage, respectively. There were three water levels—0.75 ETc (W1), 1.0 ETc (W2), 1.25 ETc (W3)—and four nitrogen levels—120 (N1), 220 (N2), 320 (N3), and 420 kg N hm−2 (N4)—and a total of 12 treatments, with the application completely randomized by using block design in the experiment. Tomato yield was improved by nitrogen supply. However, nitrogen application had a negative effect on tomato yield when the nitrogen level was applied above 320 N ha−1. The maximum water use efficiency (WUE) value of 30.5 kg m−3 was observed at W2N3, and the maximum nitrogen use efficiency (NUE) value of 684.4 kg kg−1 N was observed at W1 treatment with N1. The net photosynthetic rate of tomato leaves could be increased by reasonably increasing water and nitrogen application. The dry biomass increased with the amount of water and nitrogen in the range of (0.75–1.0) ETc and (120–320) kg ha−1. The best values of tomato quality parameters (Vc, Lycopene, soluble protein et al.) were observed at W2N3. The irrigation level of 1.0 ETc and nitrogen level of 320 N ha−1 was recommended as the best combination of water and nitrogen for greenhouse tomato cultivation in the experimental areas.

Generalized formulae for water cooling requirements for the fire safety of hydrocarbon storage tank farms

Cooling water application on hydrocarbon storage tank farms is used to prevent fire propagation between the tanks caused by intense incident radiation on the tanks adjacent to fires. Codes and standards recommendations regarding the spacing between tanks and the cooling water application rate are vague and contradicting. This study investigates a non-traditional technique using Non-Uniform Coolant Application Model (NUCAM) and illustrates the effect of utilizing this technique on coolant and land rationalization in comparison to the traditional uniform application technique. NUCAM investigates the effect of simultaneous fire propagation and domino effect scenarios on the dimensionless incident heat flux in large storage tanks using gasoline and ethanol fires at various Froude Numbers. The cooling water application rate required for total attenuation is investigated based on the rings distribution surrounding the target tank(s) at steady state conditions.Utilizing the non-uniform cooling water application techniques saves up to 59.1% of the cooling water consumption. While the savings in land area reaches 15.6%. NUCAM results regarding single fire scenarios are utilized to develop novel generalized formulae for the incident heat flux and the cooling water application rate taking into consideration the radiation fraction, Froude Number, the relative spacing between the fire and the target tanks and the relative elevation of the target with respect to the fire base. The formulae show flexibility and reliability when applied on large storage tanks range between 42 m and 55 m in diameter. These formulae provide simpler and faster solution approach for investigating the incident heat flux and the cooling water requirements for large atmospheric storage tanks that require complicated computational power for simulation using commercial packages.

An Explicit Equation for the Maximum Water Application Depth in Center Pivot Irrigation

A simple explicit formula was derived to determine the maximum irrigation depth (Dmax) that can be applied per irrigation without any runoff under a center pivot and/or linear move irrigation system. The analysis is built on the assumption that Dmax is achieved when the water application rate is tangential to the Green-Ampt infiltration rate function. The surface storage was not considered here but tillage effects can be inherently incorporated if parameters of the Green-Ampt equation are properly measured. A power form formula was proposed to simulate the infiltration rate, while the application rate pattern had a parabolic shape. The proposed equation for Dmax is a function of soil saturated hydraulic conductivity, sorptivity, and the peak application rate. Numerical examples covering different combinations of soil properties and peak application rates indicated the high accuracy of the proposed formula with maximum and average absolute errors of 1 and 0.4 mm from the numerical stepwise solution, respectively. The quick calculation of Dmax here allows us to easily estimate a minimum lateral speed that will not trigger runoff under center pivots.

Integrative Effect of Protective Structures and Irrigation Levels on Tomato Performance in Indian Hot-Arid Region.

Protected cultivation is gaining momentum in (semi) arid regions to ameliorate the adverse environmental impacts on vegetable crops, besides ensuring high resource use efficiency in resource-limiting environments. Among the less techno-intensive protected cultivation structures, naturally ventilated polyhouses (NVP), insect-proof net houses (IPN) and shade net houses (SNH) are commercial structures in India. With the aim to find the best-protected structure, together with optimum irrigation level, for high yield and water productivity of the tomato crop, the most popular crop in hot arid regions, we evaluated tomato performance in low-tech protected structures (NVP, IPN and SNH) in interaction with three irrigation levels (100, 80 and 60% of crop evapotranspiration, ETc) during spring–summer of 2019 and 2020. The NVP was found superior to both the net house structures (IPN and SNH) for different performance indicators of tomatoes under investigation. The components of plant growth (leaf and stem dry mass) and fruit yield (fruit size, weight, yield), as well as fruit quality (total soluble solids, fruit dry matter and lycopene content) were higher in NVP, regardless of irrigation level. The yield as well as water productivity were significantly higher in NVP at 100% ETc. However, there was no statistical variation for water productivity between NVP and IPN. Microclimate parameters (temperature, relative humidity and photosynthetic active radiation) were markedly more congenial for tomato cultivation in NVP followed by IPN in relation to SNH. Consequently, plants’ physiological functioning with higher leaf relative water content (RWC) and lower leaf water potential concomitantly with better photosynthetic efficiency (chlorophyll fluorescence, Fv/Fm), was in NVP and IPN. Most growth and yield attributes were depressed with the decrease in water application rates; hence, deficit irrigation in these low-tech protected structures is not feasible. For tomato cultivation in resource-scarce arid regions, the combination of the normal rate of irrigation (100% ETc) and NVP was optimal for gaining high yield as well as water productivity as compared to net houses.

Salsola soda as selenium biofortification crop under high saline and boron growing conditions.

In California, there is a shortage of good quality water available for irrigated agriculture due to severe drought. Consequently, saline groundwaters and drainage waters containing natural-occurring selenium (Se) and boron (B) salts are being considered as alternative sources of water for irrigation on salt and B tolerant crops like the edible halophyte-agretti (Salsola soda L.). In this multi-year field study, we evaluated agretti grown as a Se-biofortification crop in typical saline/B-laden soils (10 dS m−1 and 12 mg B/L) and irrigated with saline (3–8 dS m−1) and low-saline water (<1 d/S m) containing B (3–6 mg B/L) and Se (0.02–0.25 mg Se/L) at different evaporation transpiration (Eto) rates (100, 75, and 50 %, respectively). During the four-year study, fresh biomass yields ranged from 1 to 3 kg/m2 and were generally highest with irrigation at 100 % Eto with either saline or low-saline water. Tissue Se concentrations ranged from 2 to 3.2 mg Se / kg DW and 0.4–0.5 mg Se/kg DW with saline and low-saline irrigation, respectively. Selenium speciation in plant tissue showed the following: selenomethionine (SeMet) > selenate (SeO4) > methylselenocysteine (MeSeCys), irrespective of any treatment (i.e., year of planting, saline or low saline irrigation, rate of water application, direct seeding or transplanted). Agretti did not exhibit any toxicity symptoms as indicated by changes in total phenolic concentrations. Total phenolics ranged from 180 to 257 GAE/L and showed no significant differences among all treatments, although they were generally higher at the lowest water treatment (50% Eto). In regard to toxic ion accumulation, agretti tolerated excessive sodium (Na) and boron (B) and tissue concentrations ranging from 5.5 to 8.8% Na and 60 to 235 mg B/kg DW, respectively. Results from this multi-year study have identified a unique Se-biofortification strategy for producing Se-enriched agretti using saline, B- and Se-laden soil and irrigating with saline and low-saline water, respectively. Successful production of this crop may promote Se- biofortification strategies in poor quality regions where natural- occurring Se is present in soils and in waters used for irrigation.

A Spraying Model of Non-atomizing Sprinkler based on Jet Fragmentation

This work is devoted to the development of a new model for the non-atomizing sprinkler irrigation jet, for calculating the trajectories and landing positions of water droplets. The novelty of the proposed model is that the secondary breakup of the droplets can be calculated during the spraying process. For irrigation jet with a second wind-induced breakup regime, the model is optimized based on the ballistic theory by considering the secondary breakup of droplets and the jet breakup length. The wave-breaking model is used to determine the secondary breakup of the droplets. The output of this model is the water application rate that is calculated by using the cumulative volume of droplets along the radial spraying direction. A comparison of the results obtained using the proposed model with experimental data is conducted to verify the accuracy and reliability of the proposed model. The results show a good agreement of the peak water application rate between the optimized model and the experimental data, with an average error ranging within 6%. The droplets in the front spraying area usually have a diameter of 0-2 mm. This is computed by using the droplet secondary breakup sub-model, resulting in a considerably improved accuracy of the optimized model in the prediction of the water application rate of a sprinkler.

Water requirements for growth and survival of Swietenia macrophylla and Tabebuia heterophylla juvenile trees in relation to water production capacity of dew condensers

Drought mortality of juvenile trees is a major cause for failure ofreforestation projects. Portable devices such as passive radiative dew condensers can often provide 0.15 L/day of water in situ, possibly sufficient for tree survival until roots can access groundwater, allowingself-sustainability. To evaluate growth and survivability of juvenile trees of Tabebuia heterophylla Britton and Swietenia macrophylla King under suchlow water amounts, juvenile trees received approximately 0.033, 0.067, 0.134, 0.201 and 0.268 L/tree/day, representing fractions (relative evapotranspirationor RET) of 0.125, 0.25, 0.50, 0.75 and 1.00 of the evapotranspiration demand (ETo). The experiment lasted 60 days for S. macrophylla and 90 days for T. heterophylla. All T. heterophylla juvenile trees survived even at the lowestirrigation rate. However, S. macrophylla juvenile trees began dying at RET &lt; 0.5, with only 60 percent surviving at RET = 0.25 (0.067 L/day) and 100 percentmortality occurring at RET = 0.125 (0.033 L/day). Water requirements of 0.134 L/day, necessary for full survival of both species, were within the typical production capacity of 1-m2 dew condensers. However, a greater safetyfactor is obtained using drought tolerant species such as T. heterophylla, which can survive under water application rates as low as 0.03 L/day.

Dual-Diameter Laterals in Center-Pivot Irrigation System

Design strategies to enhance modern irrigation practices, reduce energy consumption, and improve water use efficiency and crop yields are fundamental for sustainability. Concerning Center-Pivot Irrigation Systems, different design procedures aimed at optimizing water use efficiency have been proposed. Recently, following a gradually decreasing sprinkler spacing along the pivot lateral with constant diameter and sprinkler flow rate, a new design method providing a uniform water application rate has been introduced. However, no suggestions were given to design multiple-diameter laterals characterized by different values of the inside pipe diameter. In this paper, first the previous design procedure is briefly summarized. Then, for the dual-diameter center pivot laterals a design procedure is presented, which makes it possible to determine pipe diameters that always provide sprinkler pressure heads within an admitted range. The results showed that for the assigned input parameters, many suitable solutions can be selected. The lateral pressure head distributions were compared to those derived by the common numerical step by step solutions, validating the suggested simplified procedure. An error analysis was performed, showing that the relative error, in pressure heads, RE, was less than 2.3%. If imposing the mean weight diameter, Dm, equal to its minimum value, the optimal pressure head tolerance of the outer lateral, δI, amounting to about 2%, with the RE in pressure heads being less than 0.4%, which makes the suggested procedure very accurate. Several applications were performed, compared, and discussed.

Experimental Study on Droplet Characteristics of Rotating Sprinklers with Circular Nozzles and Diffuser

The characteristics of spray droplets are important for calculating the hydraulic performance of sprinklers. In order to evaluate the effects of working pressure and nozzle diameter on the near ground droplet characteristics of the Nelson R33 sprinkler, an experiment was conducted to test the droplet size and velocity by using a two-dimensional video disdrometer (2DVD). Based on the water application rate, droplet diameter and velocity, the kinetic energy was calculated. The results show that there is an exponential positive correlation between the range and the volume-weighted mean particle size of droplets (VMD). The average kinetic energy of a single droplet fits well with the power function model. Under the minimum pressure of 200 kPa, the diameter and kinetic energy of droplets are large, and the peak values are 5.67 mm and 0.0092 J, which are 1.14 to 1.62 times and 1.18 to 5.68 times those of other working conditions, respectively. When the nozzle diameter is the smallest (4.4 mm), the droplet diameter and peak kinetic energy are 1.12 to 1.58 times and 1.02 to 1.26 times higher than 4.8 and 5.2 mm. Therefore, it is not recommended to work under the condition of less than 250 kPa, and a small-diameter nozzle should be selected while ensuring uniform kinetic energy.

Assessing irrigation mitigating drought impacts on crop yields with an integrated modeling framework

Irrigation is one of the major adaptation strategies to combat the negative impacts of drought on crop yields. However, during droughts, the water resources are limited and determining the exact irrigation amount and its response to crop yields are crucial. Existing crop yield simulation models are data-intensive and a majority of these are point-based. Therefore, this study presents a novel integrated modeling framework by using two parsimonious models (CROPWAT, an irrigation water requirement simulation model; and AquaCrop-GIS, a spatial crop yield simulation model) to simulate corn and soybean yields under different irrigation application rates during drought years at a spatial scale in the Mobile River Basin (MRB), Southeast U.S. To simulate crop yields for drought years, first agricultural drought years are identified using an integrated drought index called the Standardized Precipitation Evapotranspiration Soil Moisture Index (SPESMI). The results indicate that a majority of the basin was affected by mild to extreme droughts during the years 2008, 2011, 2012, 2016. The results of the integrated modeling framework illustrate the potential corn and soybean yields can be increased from 10% to 259% and 20% to 229% respectively under different irrigation water application rates (50%, 75%, and 100% of irrigation water requirement) relative to rainfed crop yields at the counties in the MRB during drought years. These findings demonstrate the importance of overall irrigation and the integrated modeling framework in devising robust irrigation water management plans in drought-affected areas at a spatial scale. Failure in integrating irrigation water requirement models in crop yield simulations will result in erroneous yield simulations, especially during droughts – this is salient given projections for frequent and intense droughts globally. Although the study is focused on MRB, the framework developed is applicable for irrigation planners and water managers in any region that experiences mild to extreme droughts, as long as the farmers have the ability to adapt the irrigation in their practice given socio-economic constraints.

Impacts of climate and weather on irrigation technology adoption and agricultural water use in the U.S. pacific northwest

AbstractIn this article, we model long‐run responses to climate expectations that are predetermined before the growing season and short‐run responses to weather realizations during the growing season. The model is applied to a climatically diverse region, the U.S. Pacific Northwest, and the most comprehensive dataset on irrigation in the United States to estimate the impact of extreme weather on irrigation technology adoption and agricultural water use. Impacts on agricultural water use were driven more by adjustments to irrigated acreage (extensive margin effects) than by adjustments to the water application rate (intensive margin effects). The model captures the two mechanisms for irrigation to mitigate freeze damage to crops: wetting the soil (heat retention) and over‐head sprinkler irrigation (latent heat). Realized late spring freeze caused water use for orchard/vineyard to increase by 3%, but this represents less than a 1% increase in total agricultural water use. Expected spring freeze variability encouraged adoption of sprinkler irrigation technology for some crops.

Insights into Efficient Irrigation of Urban Landscapes: Analysis Using Remote Sensing, Parcel Data, Water Use, and Tiered Rates

To understand how landscape irrigation can be better managed, we selected two urban irrigation systems in northern Utah, USA, and performed a statistical analysis of relationships among water use, irrigated area, plant health (based on the Normalized Difference Vegetation Index), and water rate structures across thousands of parcels. Our approach combined remote sensing with 4-band imagery and on-site measurements from water meters. We present five key findings that can lead to more efficient irrigation practices. First, tiered water rates result in less water use when compared to flat water rates for comparable plant health. Second, plant health does not strictly increase with water application but has an optimum point beyond which further watering is not beneficial. Third, many water users irrigate beyond this optimum point, suggesting that there is water conservation potential without loss of aesthetics. Fourth, irrigation is not the only contributor to plant health, and other factors need more attention in research and in water conservation programs. Fifth, smaller irrigated areas correlate with higher water application rates, an observation that may inform future land use decisions. These findings are especially pertinent in responding to the current drought in the western United States.

Comparisons of Spray Characteristics between Non-circular and Circular Nozzles with Rotating Sprinklers

HighlightsExperiments were conducted to investigate the hydraulic performance of the solid-set rotating sprinkler.The effects of nozzle shape and working pressure on the droplet characteristics and kinetic energy of the rotating sprinkler were analyzed.The circular nozzle has a large wetting radius and large droplet size.Use of a non-circular nozzle could result in higher irrigation uniformity and lower kinetic energy imparted to the soil surface by water droplets under low working pressures.Abstract. Reducing the working pressure of sprinklers can effectively reduce sprinkler irrigation energy requirements. However, the reduction in working pressure and variation of nozzle shape inevitably lead to changes in the hydraulic performance of the sprinkler. To evaluate the spray characteristics of selected non-circular (the shape of the nozzle opening was asymmetric) and circular nozzles at low pressure, experiments were conducted to investigate the effects of working pressure, nozzle shape, and nozzle diameter on flow rate, radius of throw, water application rate, droplet size, droplet velocity of the rotating sprinkler, and kinetic energy of the water droplets impacting on the soil surface. The coefficients of irrigation uniformity were calculated for the non-circular and circular nozzles under different rectangular sprinkler spacing and working pressures. The results show that the flow rates of the non-circular and circular nozzles were equal under the same working pressure and with the same nozzle size, while the throw radius of the circular nozzle was longer than that of the non-circular nozzle. The circular nozzle produced a larger droplet size than the non-circular nozzle did. Since the droplet size and kinetic energy per unit droplet volume increased along the radius of throw, and the peak water application rate of the circular nozzle was located near the perimeter of the radius of throw, the peak specific power impact on the soil surface by the water droplets of the circular nozzle was greaterspecifically, 1.26 to 1.97 times that of the non-circular nozzle. With the increase in working pressure, the peak values of specific power and water application rate decreased. The irrigation uniformity coefficients of the non-circular and circular nozzles were more than 85% within the recommended pressure range of the manufacturer when the sprinkler spacing was less than 11 m. It was easier to obtain higher irrigation uniformity and lower impact kinetic energy under low working pressure when using a non-circular nozzle. Keywords: Application rate, Irrigation uniformity, Kinetic energy, Sprinkler irrigation, Working condition.

Explosion risk-based water spray mitigation analysis of ultra-deep-water semi-submersible platforms

Water spray is an economical and environment-friendly alternative to mitigate gas explosion. This study conducts explosion risk analysis (ERA)-based water spray mitigation analysis of ultra-deep-water semi-submersible platform. 5000 gas explosion simulations with and without water spray are conducted by using FLACS codes. The outcome demonstrates that water spray with droplet size 700 μm and water application rate (WAR) 26 L/m2 min is most effective to mitigate explosion scenarios. The droplet size is the significant factor to stimulate the mitigation effect of water spray under middle and small exceedance frequencies, e.g., 1E-05 and 1E-06. WAR becomes dominate to awaken the water spray's negative effect under large exceedance frequency, e.g., 1E-04. A precise and efficient approach of BRANN integrated with artificial bee colony optimization algorithm is used to determine the optimal water spray configuration given the desirable exceedance frequency and the expected design accidental load that the ultra-deep-water semi-submersible platform structures could resist.

Growth, water use, and crop coefficients of direct-seeded guayule with furrow and subsurface drip irrigation in Arizona

Crop establishment costs of guayule (Parthenium argentatum A. Gray), a perennial desert shrub that produces natural rubber, can be significantly reduced using direct seeding rather than the traditional practice of transplanting greenhouse-grown seedlings. However, information regarding the irrigation application, crop evapotranspiration (ETc), and crop coefficients (Kc) for managing direct-seeded guayule crops has not been provided. In this study, guayule was direct-seeded in Apr. 2018 in fields at two location in Arizona; Maricopa, on a sandy loam soil and Eloy, on a clay soil, and harvested 23–24 months later in 2020. At each location, five irrigation rates were applied with subsurface drip irrigation (SDI) ranging from 50 to 150 % replacement of ETc (denoted as D50 to D150 treatments), respectively. A 6th treatment using furrow irrigation at 100 % ETc replacement (F100) was included. Treatments were replicated three times. The ETc was estimated for the first 74–84 days of crop establishment and thereafter, actual ETc (ETc act) was determined weekly-biweekly for the D100 and F100 treatments using a soil water balance. The objectives were to evaluate the responses in dry biomass (DB), rubber yield (RY), and resin (ReY) yield to water application rate, develop irrigation management criteria for the two soil types, and determine the ETc and crop coefficients for the 100 % treatments.The total irrigation applied to treatments ranged from 1830−1910 mm to 5090–5470 and averaged 3590 and 3320 mm for the 100 % SDI (D100) and furrow (F100) treatments at Maricopa and Eloy, respectively. The summed estimated ETc plus ETc act for the D100 and F100 treatments were 3663 and 3506 mm at Maricopa, respectively and 3428 and 3320 at Eloy, respectively. Average measured mid-season Kc in the 1st year varied from 1.20 to 1.26. Average measured mid-season Kc in the 2nd year were higher for D100 (≈1.30) than for F100 (≈1.23). Adjusted to the standard climate proposed in FAO56, mid-season Kc are 1.24 for D100 and 1.17 for F100 in the 2nd year. Average DB at Eloy (28.6 Mg ha−1) was not significantly higher than at Maricopa (24.0 Mg ha−1). However, RY and ReY were both significantly higher at Maricopa. At each location, rubber content was significantly higher for the F100 and the two lowest SDI rates than for other treatments. The highest mean RY and ReY were achieved with D100 at Maricopa and D75 at Eloy. These two also had significantly greater water productivity (WP; DB, RY, and ReY per unit of total water applied) than those at higher SDI rates and the F100 treatments. RY and ReY and their WP were generally higher for D100 than F100 in the sandy loam but not in the clay soil. For direct-seeded guayule in clay soils, furrow irrigation should be considered due to the lower rubber content and higher costs associated with SDI.

Nitrogen and phosphorus losses by surface runoff and soil microbial communities in a paddy field with different irrigation and fertilization managements.

Rice cultivation usually involves high water and fertilizer application rates leading to the nonpoint pollution of surface waters with phosphorus (P) and nitrogen (N). Here, a 10-year field experiment was conducted to investigate N and P losses and their impact factors under different irrigation and fertilization regimes. Results indicated that T2 (Chemical fertilizer of 240 kg N ha-1, 52 kg P ha-1, and 198 kg K ha-1 combined with shallow intermittent irrigation) decreased N loss by 48.9% compared with T1 (Chemical fertilizer of 273 kg N ha-1, 59 kg P ha-1, and 112 kg K ha-1 combined with traditional flooding irrigation). The loss ratio (total N loss loading/amount of applied N) of N was 9.24-15.90%, whereas that of P was 1.13-1.31% in all treatments. Nitrate N (NO3--N) loss was the major proportion accounting for 88.30-90.65% of dissolved inorganic N loss through surface runoff. Moreover, the N runoff loss was mainly due to high fertilizer input, soil NO3--N, and ammonium N (NH4+-N) contents. In addition, the N loss was accelerated by Bacteroidetes, Proteobacteria, Planotomycetes, Nitrospirae, Firmicutes bacteria and Ascomycota fungi, but decreased by Chytridiomycota fungi whose contribution to the N transformation process. Furthermore, T2 increased agronomic N use efficiency (AEN) and rice yield by 32.81% and 7.36%, respectively, in comparison with T1. These findings demonstrated that T2 might be an effective approach to ameliorate soil chemical properties, regulate microbial community structure, increase AEN and consequently reduce N losses as well as maintaining rice yields in the present study.

Hydraulic Design of the Center-Pivot Irrigation System for Gradually Decreasing Sprinkler Spacing

Design strategies that enhance modern irrigation practices, reduce energy consumption, and improve water use efficiency and crop yields are fundamental for sustainability. Although microirrigation is currently a widely applied method, center-pivot irrigation systems have become very popular on large farms, thanks to their automation, wide-coverage, and reliability. Different design procedures have been proposed, even though some aspects have not been solved yet. This paper presents a simple design procedure for center-pivot systems using a gradually decreasing sprinkler spacing along with a pivot lateral, which makes it possible to set favorable and uniformly distributed water application rates. The sprinkler spacing distribution along the radial direction is derived by considering just one dimensionless group accounting for the geometric and hydraulic input parameters. According to this outcome, the results showed that the suggested procedure made it possible to select the sprinkler characteristics and the pipe diameter based on the desired input parameters, i.e., the uniform water application rate and the lateral length. For assigned input parameters, the lateral length is delimited by a threshold value, indicating that lateral lengths longer than that threshold value require the modifications of a sprinkler flow rate or pipe diameter. Finally, applications based on the proposed hydraulic design procedure were performed and discussed for two different cases.

Optimal allocation of agricultural water resources under the background of China's agricultural water price reform-a case study of Heilongjiang province

To improve the performance of agricultural water resources and food production against a background of China's agricultural water price reform, an interval two-stage stochastic programming model is established and applied to account for impacts of agricultural water price reform and a water-saving technology subsidy in Heilongjiang Province, China. A water price affordability constraint and a water-saving technology subsidy to support uptake of water-saving irrigation technology are both introduced. Results of model runs show that when the current agricultural water price is increased to reflect national water price reform without a technology subsidy, the total income of irrigation farming is reduced by 2%-8%, with potential negative impacts on food production. However when an irrigation water-saving technology subsidy is introduced to accompany the increased water price, farm income can be protected and overall food production can be maintained. The two part mechanism of increased water price and water-saving technology subsidy can be used to encourage farmer to reduce water application rates as well as reduce land in production of high-water-consuming crops. Such a two part program offers considerable hope for protecting unsustainable use of water in water scarce regions while protecting farm income and food security in the face of unknown future water supply fluctuations.

Feasibility studies on raingun method of irrigation system in groundnut

A field study was conducted on groundnut by using different irrigation techniques, such as raingun, check basin and sprinkler irrigation systems. In our country, raingun method of irrigation is becoming more popular for sugarcane due to convince in shifting. Sufficient information such as coefficient of discharge, percentage of overlapped diameter for uniformity, etc. is not available for designing the raingun system. A medium volume raingun model was operated at different operating pressures of 2.0, 2.5 and 3.0 kg.cm-2 with 14mm diameter nozzle. The discharge was found increasing with increase in pressure head for raingun of nozzle size 14mm was 3 kg.cm-2. It was observed that increase in pressure increased the discharge of medium volume raingun irrigation system. The minimum discharge was observed at 2 kg.cm–2 as 10.30 m3.h–1 for 14mm diameter nozzle. The maximum discharged was observed at 3 kg.cm-2 as 12.13 m3.h–1 for 14mm diameter nozzle. The coefficient of uniformity of the raingun was determined at different operating pressure. The high coefficient of uniformity was found at 3 kg.cm-2 operating pressure and low uniformity of coefficient was found at 2 kg.cm-2 operating pressure. The water application rates of the raingun under various pressures were determined. The maximum application rate of 10.86 mm.h–1 was found at 2 kg.cm-2 and the minimum application rate of 9.32 mm.h-1 was found at 3 kg.cm-2. The water use efficiency was maximum in case of raingun method of irrigation as compared to check basin and sprinkler irrigation system. Use of raingun sprinkler irrigation during early crop season helped in saving water when the soil infiltration rate was very high and need of water in the root zone was less. Using raingun method of irrigation system, 0.79 kg.m-3 higher water use efficiency was achieved as compared to check basin and sprinkler irrigation system. Benefit cost ratio of the raingun method of irrigation was found as 1.05, which indicated that the raingun method of irrigation was economically feasible.

Effects of Plate Structure and Nozzle Diameter on Hydraulic Performance of Fixed Spray Plate Sprinklers at Low Working Pressures

HighlightsThe hydraulic performance of fixed spray plate sprinklers (FSPS) was evaluated at low working pressures.The effects of geometric structure on the hydraulic performance of FSPS were studied.A model was developed for estimating the application depth and uniformity of FSPS under a linear-move system.The recommended values of the most effective sprinkler combination spacing for FSPS are given.Abstract. Reducing the working pressure of sprinklers can effectively reduce the energy consumption of sprinkler irrigation systems. Fixed spray plate sprinklers (FSPS) have a simple structure, and their working pressure has potential to be reduced to 40 kPa. To evaluate the hydraulic performance of FSPS at low pressure, an experiment was conducted to investigate the effects of working pressure, plate structure, and nozzle diameter on sprinkler flow rate, wetted radius, and water application distribution. Two plates (FSPSB and FSPSY) and five nozzles were used in the tests. The cumulative water application depth and irrigation uniformity coefficient were calculated under a linear-move system. The results show that sprinklers with larger nozzle diameters and higher working pressures produce greater coefficients of discharge. The wetted radius gradually increases with the increase in working pressure and nozzle diameter. Two empirical equations for estimating the wetted radius of the two plates are proposed. The FSPSB has a concave trajectory structure that produces a longer wetted radius than the FSPSY, which has a flat trajectory structure. Along the wetted radius, the water application rate increases and then decreases, with a peak value at a certain distance. For the FSPSB, the peak rate of water application decreases with increasing working pressure. However, the FSPSY shows the opposite trend, with the maximum peak value occurring at the highest working pressure of 250 kPa. The water distribution for a single FSPSB sprinkler is discrete due to the greater water dispersal caused by the deeper grooves in the plate. In contrast, a single FSPSY sprinkler provides a more uniform water distribution. The irrigation uniformity of the FSPSY is higher than that of the FSPSB. The recommended values for the most effective sprinkler combination spacings for FSPSB and FSPSY are given in this article. The results may be useful for selecting appropriate sprinklers in hydraulic design procedures. Keywords: Cumulative spray water depth, Irrigation uniformity, Sprinkler irrigation, Water distribution, Working condition.