Assessment of Treated Wastewater Reuse in Drip Irrigation under Different Pressure Conditions

This study aims to investigate the influence of treated wastewater (TWW) on the hydraulic performance of drip irrigation emitters. A field experiment was conducted in order to test two types of online emitters, a low pressure (LP) and a standard pressure (SP), at different working pressures (0.25 bar, 0.50 bar, and 1.00 bar) using TWW. The emitters were initially evaluated in the laboratory and the field for the discharge exponent (X), discharge coefficient (Kd), average emitter discharge (Qavg), coefficient of variation (CV), distribution uniformity (DU), the mean discharge ratio (Dra), and the main degree of clogging (DC). The main effect of the emitters on the hydraulic parameters of irrigation performance was not significant, while the operational pressure and operational time of irrigation had a significant effect. For the LP emitter, the average emitter discharge was 7.6, 7.7, and 7.8 Lh−1 at 0.25, 0.50, and 1.00 bar, respectively. For the SP emitter, the average emitter discharge was 7.6, 7.8, and 7.8 Lh−1 at 0.25, 0.50, and 1.00 bar, respectively. The EU values for the LP and SP emitters varied from low to moderate at 0.25 bar, as the EU values at 0.50 and 1.00 bar were considered high for both emitter types.

Evaluation of Root Water Uptake and Urea Fertigation Distribution under Subsurface Drip Irrigation

Shallow groundwater contamination by nitrate is frequent in agricultural lands in Egypt because of the use of urea fertilizers. The urea transformation process in the vadose zone was simulated using a HYDRUS-2D model, Software package for simulations of 2D movement of water, heat, and multiple solutes in variably saturated media, for subsurface drip irrigation. The root water and nutrient uptake were assessed for three soil types (sandy loam, loam, and silty loam) with three emitter discharge levels (1.0 L h−1, 1.50 L h−1, and 2.0 L h−1), for a comparison of three fertigation strategies (A) at the beginning, (B) at the end, and (C) at the middle of the irrigation cycle. The extension of the wetted area mainly depends on soil hydraulic conductivity. The high emitter discharge with a short irrigation time is suitable for shallow-rooted crops. The cumulative flux was highest for silty loam soil and the lowest was for the sandy loam soil (1891, and 1824 cm3) for the 2 L h−1 emitter discharge within the 35 days simulation. The cumulative drainage significantly differs among soil types with little effect of emitter discharge. It recorded 1213, 295, 11.9 cm3 for sandy loam, loam, silty loam, respectively. Urea transformation is controlled by hydrolysis and nitrification as well as the adsorption coefficient of ammonium. Nitrate distribution is mainly governed by soil type rather than the emitter discharge where the sandy loam soil is more highly susceptible to nitrate leaching than to silty loam. Nitrate concentration has recorded the minimum possible level when applying the urea fertilizer at the beginning of the irrigation event for sandy loam and loam soil while for the silty loam soil, urea application at the middle of the irrigation event is more effective. Urea application at the end of the irrigation event gives the highest accumulated leached nitrate concentration below the root zone and should be avoided (the worst strategy).

Effect of Emulsifying Petroleum Derivatives, Water Deficit Treatment and Emitters Discharge on Dry Weight, Grain yield and Water use Efficiency of Sunflower (Helianthus annuus L.)

A field experiment was conducted in Qurnah district, Basrah province on clay soil to study the effect of six treatments of emulsifying petroleum derivatives with irrigation water by using emulsifying agent adding directly to soil surface, gas oil with two ratios of 0.3% (g3) and 0.5% (g5) w/w of soil dry weight, two admixture treatments of fuel oil and gas oil (1:1) with two ratio 0.3%(go3) and 0.5% (go5), fuel oil 0.3% (o3) and control treatment 0% (c) without any addition. The effect of water deficit factor also studied with two levels 0.85 (w1) and 0.65 (w2) of available water by using drip irrigation with two emitters; low discharge 5 Lhr-1 (Ld) and high discharge 15Lhr-1(Hd). The results showed that all emulsified derivative conditioners significantly increased dry weight, grain yield and water use efficiency calculated for dry weight WUE (d) and grain WUE (g) of sunflower compared with control treatment, especially at g5 and go5 treatments which recorded the highest values. Soil capability for saving water and available water increased as a result of the addition of emulsified oil derivatives, which contributed to increase the interval time between irrigation periods and reduce the quantity of irrigation water with less value appearing at g5 and go5 under 65% water deficit treatment by using 15 Lhr-1 emitter discharge. Increasing emitter discharge from 5 to 15 L hr -1, and increasing irrigation deficit from 0.65 to 0.85 led to increasing all growth parameters, except water use efficiency.

Effect of Soil Texture on Water Movement of Porous Ceramic Emitters: A Simulation Study

Choosing reasonable design parameters for ceramic emitters used in subsurface irrigation is important for reducing the deep percolation of water and improving the water use efficiency. Laboratory experiments and numerical simulations with the HYDRUS-2D software were carried out to analyze the effect of soil texture on the infiltration characteristics of porous ceramic emitters used for subsurface irrigation. HYDRUS-2D predictions of emitter discharge in soil and wetting front are in agreement with experimental results, and the HYDRUS-2D model can be used to accurately simulate soil water movement during subsurface irrigation with ceramic emitters in different soil textures. Results show that soil texture has a significant effect on emitter discharge, soil matrix potential around the emitter, and wetting front. For 12 different soil textures, the aspect ratio of the wetting front is basically between 0.84–1.49. In sandy soil, the wetting front mainly appears as an ellipse; but in the clay, the wetting front is closer to a circle. As irrigation time increases, emitter discharge gradually decreases to a stable value; however, emitter discharge in different texture soils is quite different. In order to improve the crop water use efficiency in sandy soil, soil water retention can be improved by adding a clay interlayer or adding water retention agent, reducing the risk of deep percolation and improving the water use efficiency.

Experimental and Numerical Analysis of Drip Tape Layout for Irrigation of Sugarcane in Latosol

A laboratory soil column experiment was first conducted to analyze water movement in latosol of sugarcane field under drip irrigation from single-point source at different emitter discharge rates. Next, a mathematical model of soil water movement under drip irrigation from single-point source was built using Hydrus-3D, which could accurately simulate the shape of the wetted soil volume and the distribution of volumetric water content in the experiment. Further, a Hydrus- 3D model of soil water movement under drip irrigation from double-point source was built and then used to analyze the effects of critical parameters on irrigation uniformity. Results showed that emitter spacing affected irrigation uniformity greatly, but emitter discharge rate did not. According to the irrigation uniformity, project cost and operational management patterns, appropriate drip tape parameters for irrigation of sugarcane in latosol were determined: emitter discharge rate 1.38 L/h, emitter spacing 30 cm, and single-emitter irrigation volume 9.0 L.

Field evaluation of the performance of different irrigation emitter types using treated wastewater

Experimental tests are carried out to evaluate the impact of treated wastewater (TWW) on the discharge of five different types of emitters which are commonly used. Two water qualities, fresh water (FW) and treated wastewater, and five types of emitters, GR, Nein (NE), Edin (ED), Corona (CO), and Rain Bird (RB) are tested. The values of chemical properties for FW show mostly low clogging potential on emitter performance. The clogging potential for TWW varied from low to medium. The exception was for pH where there was severe clogging potential for both water types. The performance of emitters was tested by measuring the emitter discharge and estimating the average emitter discharge (Qavg), coefficient of variation (CV), emission uniformity coefficient (EU), and Christiansen uniformity coefficient (CU). The average discharges for different types of emitters were analyzed and compared at P ≤ 0.05. The CO and RB emitter types did not show any signs of clogging whereas the GR, NE, and ED emitter types showed signs of clogging. The results of CV, EU, and CU values showed that the performances of emitter types GR, NE, ED were classified as low or moderate clogging potential. In contrast, the CO and RB emitters were classified as moderate or high clogging potential.