The effect of papermill wastewater irrigation and gypsum soil amendments on sodium accumulation by cottonwood and soil

Gypsum soil amendments affected the concentrations of sodium in the stems and leaves of Populus seedlings irrigated with pulpmill effluent. Concentrations of sodium in the sapling tissues increased with gypsum applications which gave total calcium application rates of 175 mg Cal⁻¹ wastewater (ww) and decreased as calcium application rates were increased to 625 mg Cal⁻¹ ww. Conversely, stem biomass production decreased as calcium application rates increased to 175 mg Cal⁻¹ ww and then increased as calcium application increased to 625 mg Cal^t1̄ ww. This resulted in no significant differences across treatment in either total sodium uptake or removal of sodium from the soil by the Populus seedlings. Total sodium uptake by Populus was about 0.002% of wastewater inputs. Infiltration rate increased with the increasing gypsum application. Gypsum application rate was not associated with differences in the concentration and distribution of sodium in the soil profile but increased application rates were associated with decreased soil pH.     

Induction of soil water repellency following irrigation with treated wastewater: effects of irrigation water quality and soil texture

We hypothesized that organic matter (OM) content originating from treated wastewater (TWW) irrigation and soil texture dominate the intensity of soil water repellency. The relationship between soil texture, wastewater treatment level, and water repellency was examined in a 3-year lysimeter experiment (2008–2010). Soil type–water quality combinations, consisting of three soils with different specific surface area (SSA) and four levels of water quality differing in OM content, were tested. In each year, water repellency developed in all TWW quality treatments, but not in freshwater-irrigated controls. At the end of each year (except 2009), the highest degree of repellency was exhibited by sandy soil treated with the lowest quality TWW (highest OM content). The lowest degree of water repellency was consistently exhibited by the soil with the highest SSA irrigated with the highest quality TWW (lowest OM content). Water quality, rather than SSA, was the dominant factor in determining degree of repellency induced by TWW irrigation.     

Effects of wastewater irrigation on soil sodicity and nutrient leaching in calcareous soils

Soil column studies were conducted with two soils to assess the effects of irrigation with wastewater on soil and groundwater quality. Upon the application of wastewater, exchange occurred between solution sodium (Na⁺) and exchangeable cations (Ca²⁺, Mg²⁺, K⁺), whereby these cations were released into solution. The average exchangeable sodium percentage (ESP) of the soils increased during leaching from 9 to 21 and 28.8 to 29.7 after applying 5.0 and 3.5 l (about 7 and 6 pore volumes) of wastewater to the soils columns, respectively. Adverse effect of high Na⁺ concentration in the wastewater on raising ESP was less pronounced in the soil having initial high ESP than in the soil with low initial ESP. Salinity of the soils was also increased with the application of wastewater and Mg²⁺ and K⁺ were leached from the soils. These losses would be more severe on soils having a low cation exchange capacity and if, uncorrected could lead eventually to their deficiencies for plant growth. When the soil columns were leached with distilled water the flow rate of one soil decreased to zero after 2.2 pore volume indicating damage to soil structure. Irrigation with wastewater, which is generally more sodic and saline than regional groundwater, increases the rate of soil sodification of shallow groundwater. A relatively simple chromatographic model was used to estimate final ESP profiles in the soils assuming the condition of local equilibrium. This approach had a limited success for one of the soil. Since the final leached concentrations are in good agreement with those of wastewater, we attribute these differences to non-uniform flow through the column. In terms of practical soil and water management, our study reveals that relatively simple means can be useful to predict the water quality in soils, their discharge to ground water, and the hazard of soil structure deterioration.     

Fouling formation and chemical control in drip irrigation systems using treated wastewater

Drip irrigation systems are prone to changes in flow rate (FR) and increasing coefficients of variation (CV) when fed with treated wastewater, due to fouling inside the drippers. A model system was designed to measure the FR and fouling accumulation in laterals and drippers under different treatment conditions. A novel approach was taken to compare the different maintenance treatments. A comparison of chlorination and acidification strategies showed that daily chlorination and periodic acidification may prolong proper functioning of the drippers by maintaining a normal FR [(up to ±7 %) of nominal FR] and CV (<7 %) index in correlation with low fouling accumulation in the pipeline (<0.01 mg deposit/cm _pipe ² ). Current recommendations for the frequency of conventional treatments were found to be insufficient. Chemical analyses of the fouling inside the dripper and accumulated on the pipe wall showed that biofilm can survive inside the dripper under harsh environmental conditions, even when the pipeline stays clean. These results shed light on biofilm growth and survival mechanisms inside the dripper and may pave the way to developing new treatments or improving dripper design.     

Olive mill wastewater irrigation of maize: Impacts on soil and groundwater

The environmental impact of irrigating a maize field with weathered olive mill wastewater (OMW) for 5 years was assessed. The use of the weathered OMW added the following concentrations of nutrients to the field: 11.8 t/ha/yr carbon, 1033 kg/ha/yr total nitrogen, 23.8 kg/ha/yr phosphorous and 4161 kg/ha/yr potassium. The maize field received 6 times more nitrogen, 50 times more potassium and 2 times less phosphorous than the recommended fertilization rates. The presence of carbon increased microbial activity for organic nitrogen breakdown and the decomposition rate of organic nitrogen. No significant increase was observed of heavy metal accumulation in the soil. Electrical conductivity in the soil remained below the salinization threshold. No direct exposure values were exceeded. No impact on groundwater quality was observed. Irrigation of crops like maize with weathered OMW could be part of a viable decentralized solution for olive mill wastewater use in areas with low organic matter and high irrigation demand.     

The effect of deficit irrigation with treated wastewater on sweet corn: experimental and modelling study using SALTMED model

This study investigated the impact of using treated wastewater and deficit irrigation on yield, water productivity, dry matter and soil moisture availability. The experiment included six treatments of deficit irrigation with treated wastewater during the 2010 and 2011 seasons and two deficit irrigation treatments combined with 3 organic amendment levels during the 2012 season. The experimental and SALTMED modelling results indicated that regulated deficit irrigation when applied during vegetative growth stage could stimulate root development, increase water and nutrient uptake and subsequently increase the yield. The organic amendment has slightly improved yield under full irrigation but had relatively small effect under stress conditions. The SALTMED model results supported and matched the experimental results and showed similar differences among the different treatments. The model proved its ability to predict soil moisture availability, yield, water productivity and total dry matter for three growing seasons under several deficit irrigation strategies using treated wastewater. The high values of the coefficient of determination R ² reflected a very good agreement between the model and observed values. The SALTMED model results generally confirm the model’s ability to predict sweet corn growth and productivity under deficit irrigation strategies in the semi-arid region.     

Crop and stress coefficients in rainfed and deficit irrigation vineyards using sap flow techniques

Projected climate changes and expansion of viticulture to drier regions justify the installation and management of deficit irrigation (DI) strategies. Contradictory results on the effect of DI on crops may be ascribed to the incorrect application of these techniques. The lack of discrimination between basal crop (K _cb) and stress coefficients (K _s) can be an obstacle to proper irrigation management. A sap flow (SF) technique associated with microlysimeters and eddy covariance (EC) methods was applied to five commercial vineyards, aiming to discriminate those coefficients, during the driest period of the vegetative cycle. A comparative analysis of the coefficients, in relation to measured vegetation parameters (for K _cb) and plant water status (for K _s) is presented. K _cb, ranging from about 0.35 to 0.75, was highly correlated with leaf area index at stand level. K _s, which decreased till 0.2 in the most stressed vineyard, was well correlated to plant water status (K _s function), represented by predawn leaf water potential. K _s functions for the different experiments exhibited falling slopes with decreasing water status, with variable trends depending on the rates of maximal crop transpiration (T _m). These experimental results show that specific parameters for K _s functions, necessary to estimate water use and irrigation depths, in order to control the stress levels in DI scheduling, are also dependent on T _m.     

Impact of treated wastewater irrigation on water repellency of Mediterranean soils

Irrigation with treated wastewater (TWW) is gaining importance due to declining water availability in dry regions. TWW irrigation has various potential adverse effects on soil quality such as hydrophobic effects on soil surfaces, reducing initial sorptivity and promoting the formation of preferential flow paths. In May and June 2010, in situ infiltration measurements using mini disk tension infiltrometer were deployed in five different orchard plots in Israel to assess the impact of different irrigation water qualities on the soil water repellency index R. In most plantations, long-term test sites were accessed to compare adjacent plots irrigated with fresh water (FW) or TWW. Topsoil samples were analyzed for selected physical and chemical characteristics. The mean R values increased at all TWW sites, from +15 up to +55 % compared with FW sites. The water drop penetration time (WDPT) increased up to 30 fold at three of five TWW sites compared with FW sites. Subsequent U tests and multilevel analysis indicated an impact of the type of irrigation water on R and WDPT. Moreover, soil electrical conductivity and exchangeable sodium percentage were consistently higher at all TWW sites. These results show that irrigation water quality clearly influences physical and chemical properties of the soil.     

Water use efficiency and fruit quality of table grape under alternate partial root-zone drip irrigation

Two-year field experiments were conducted to investigate the effect of alternate partial root-zone drip irrigation on fruit yield, fruit quality and water use efficiency of table grape (Vitis vinifera L. cv Rizamat) in the arid region of northwest China. Three irrigation treatments were included, i.e. CDI (conventional drip irrigation, both sides of the root-zone irrigated), ADI (alternate drip irrigation, both sides of the root-zone irrigated alternatively with half the water) and FDI (fixed drip irrigation, only one side of the root system irrigated with half the water). Results indicated that compared to CDI, ADI kept the same photosynthetic rate (P_n) but reduced transpiration rate, thus increased leaf water use efficiency (WUE) of table grape. And diurnal variation of leaf water potential showed no significant differences during 7.00 a.m. to 14.00 p.m. in both years. ADI also produced similar yield and improved WUE_ET by 26.7–46.4% and increased the percentage of edible grape by 3.88–5.78%, vitamin C content in the fruit by 15.3–42.2% and ratio of total soluble solid concentration/titrated acid in both years as compared to CDI. Thus ADI saved irrigation water, improved the water use efficiency and fruit quality of table grape without detrimental effect on the fruit yield in arid region.     

Biological and chemical fouling in drip irrigation systems utilizing treated wastewater

A major constraint on the use of treated wastewater (TWW) in microirrigation systems is the potential for fouling. This research aimed to assess the occurrence of fouling in drip irrigation systems applying TWW and determine the quantity and chemical characteristics of the fouling. A field survey was performed to determine the incidence of chemical and biological fouling in irrigation systems and its influence on system performance. Dripper flow rate, total and volatile solids, chemical composition, and diffuse reflection infrared Fourier transform (DRIFT) spectra of the fouling material were determined. Fouling was found in all of the drip irrigation systems sampled under a variety of conditions. The fouling contained a high percentage of organic matter (OM), except for two instances where the material was mainly inorganic. Identification of the functional groups using DRIFT showed that the OM found is essentially of aliphatic and amide origin. Comparing the spectra obtained from the various sites revealed considerable similarity in the material properties. This suggests a common mechanism in all irrigation systems tested, but a different accumulation rate. A high correlation was found between total phosphorus concentration, the sum of Ca and Mg concentrations and the TWW pH, and the content of total and organic carbon in the fouling. In addition, the correlation between equipment age and the amount of accumulated total solids was high for systems containing high quantities of fouling. The concentration of volatile solids was highly correlated with the age of the irrigation system.     

Impact of treated wastewater irrigation on quality attributes and contamination of tomato fruit

A field experiment was conducted in 1999 and 2000 to investigate the effect of different treatments of potable and treated wastewater on the quality of tomato fruit (Lycopersicon esculentum L. Mill) in Jordan. Tomato seedlings (cvs. GS₁₂ and RS₅₈₉₉₅₆) were furrow irrigated with different mixtures of potable and wastewater (1:0, 1:1, 1:3, and 0:1). The BOD, and SS of the treated effluent used were 34 and 35 mg/l, respectively. Irrigation with treated wastewater did not affect fruit pH, increased their size up to 2 cm in diameter, and weight up to 78.7 g. Additionally, a decrease of 1.5% in the SSC, 0.59 kg in firmness, and 5.1% in weight loss of tomato fruit were recorded. The 0:1 application of treated wastewater resulted in an increased microbial contamination (TC 1.56×10⁴ and 4.7×10² CFU/100 g; FC 3×10² and 130 CFU/100 g; TBC 188×10² and 205×10² CFU/100 g) on the surface of the fruit (skin) for GS₁₂ and RS₅₉₉₉₅₆ varieties, respectively. There was a negligible contamination on fruit scar, and nil in fruit flesh. Contamination increased exponentially with increasing the proportions of treated wastewater application. Since treated wastewater was highly contaminated with total coliform (up to 42.0 CFU/100 ml) and total bacterial count (up to 7.820 CFU/100 ml), hence, contamination was aggravated with increasing the percentage of treated wastewater. It is suggested that the treated wastewater can be used as an alternative for irrigation of tomatoes eaten after cooking, but not for those taken as raw provided that the effluent quality is continuously monitored to avoid contamination.     

Feasibility of long-term irrigation as a treatment method for municipal wastewater using natural soil in Kuwait

Passing treated wastewater through soil is a natural and economic means to improve the quality of wastewater. The United Agricultural Production Company (UAPCO) farm located in the Sulaibiya area of Kuwait has been irrigated with tertiary treated wastewater since 1976. A field investigation at the farm has been conducted by the Kuwait Institute for Scientific Research (KISR) to assess the applicability of the natural soil treatment method, in the long term, to improve the quality of the treated wastewater under the conditions prevailing in Kuwait. The collected data have been analyzed to assess the degree of improvement in quality of the infiltrated water with respect to the tertiary wastewater used for irrigation. The data analysis indicates that in spite of low clay content of the soil, improvement in the quality of the tertiary treated wastewater through soil aquifer treatment by the removal of ammonia (>90%), iron (>80%), organic carbon (>90%), biological oxygen demand (BOD) (100%) and bacteria (50-100%, depending on its type), can be expected over a long-term period. Soil leaching, however, tends to increase the total dissolved solids of the infiltrated water and the nitrification process increases the nitrate content.     

滴灌水温对土壤入渗和土壤温度的影响

为了解水温对滴灌土壤入渗特征和土壤温度的影响,研制一套恒温试验装置,可使水温变化控制在±0.5 ℃范围内,选择5,20,35 ℃作为试验水温,进行不同水温室内滴灌入渗试验,分析各水温下土壤水分入渗和土壤温度变化特征.结果表明:在相同时段内,随滴灌水温升高,水平和垂直湿润锋运移距离增大,垂直湿润锋运移速率增大.分别建立水平、垂直湿润锋运移距离与入渗时间和滴灌水温的关系模型,决定系数R²均大于0.99.湿润土体平均含水量与入渗时间关系不大,但随入渗水温的升高而减小.土壤水分扩散率与水温成正比;水温升高,饱和导水率随之增大,二者呈指数函数关系;土壤吸持水分的能力随温度的升高而降低.不同灌溉水温改变了土体中的温度分布,随着距滴头距离的增加,由水温引起的土壤温度的变化量逐渐减小.结论可为指导大田和温室滴灌技术提供理论依据.     

Trickle irrigation timing and its effect on plant and soil water status

Tomato plants on Sinai sand dunes were irrigated daily by drip irrigation. The irrigation was supplied during daytime hours for one field and a short time after sunset for the second. Results showed that daytime irrigation of soil with low water holding capacity increased the yield significantly and improved plant water potential as well as water use efficiency. The dominant component of water balance under these conditions was found to be deep percolation, which accounted for more than 70% of the water budget. Controlling this component rather than soil water status requires measurements of flux as input for managing the quantity of water to be applied. It is concluded that during hours of high net radiation flux, transpiration rate can best compete with deep percolation rate. Based on this conclusion, the use of net radiation flux as input is recommended for the best irrigation timing.     

Soil surface water repellency induced by treated wastewater irrigation: physico-chemical characterization and quantification

Irrigation with treated wastewater (TWW) is commonly practiced in Israel to relieve freshwater (FW) shortages. We hypothesized that the organic matter (OM) originating from TWW irrigation alters the physico-chemical properties of the soil, induces water repellency in the soil’s top layer, and consequently alters water distribution in the soil profile. In measurements taken in an avocado orchard on a clayey soil, water repellency was found in TWW-irrigated plots. In addition, smaller wetted surface areas were recorded around the drippers in comparison with FW drippers. Drier zone below soil surface was observed in TWW-emitting drippers. OM extraction from the different plots exhibited differences in quantity and quality of organic substances between TWW- and FW-irrigated soils, with a higher quantity of hydrophobic substances in the TWW-irrigated soil extract.     

Effects of fixed partial root-zone drying irrigation and soil texture on water and solute dynamics in calcareous soils and corn yield

Water dynamics and salt distribution in the soil were studied under Fixed Partial Root zone Drying irrigation (FPRD) conditions in corn fields in Northern Greece. FPRD irrigation technique was applied without deficit treatment in two calcareous soils, a sandy clay loam and a sandy loam. Soil water content was recorded in the vertical profile of 0.6 m with the use of capacitance sensors in the row and interrow positions of plants. Salt built-up was monitored to the depth of the root zone, bi-weekly, by measuring electrical conductivity (EC_e) and the concentrations of soluble cations Ca²⁺, Mg²⁺, Na⁺ and K⁺ of the saturation extract on irrigated and non irrigated interrow positions. Soil moisture distribution and salt built-up in soil were used to evaluate the potentials and constraints of FPRD efficiency to sustain plant growth and crop production as a low cost drip irrigation technique. The results indicated that FPRD application on both soils was capable of supplying sufficient amounts of water on plant row. Soil analyses showed that salts accumulated to high levels in the soil surface and decreased in depth at the non irrigated interrow positions. Spatial and temporal variability of salt movement and distribution in the soil profile of 0.6 m were ascribed to soil textural differences. The development and yield of corn plants for both soils reached the usual standards for the area with a minor decrease in the sandy loam soil.     

水肥耦合对葡萄土壤环境及品质影响的研究

水肥耦合是利用以水促肥，以肥调水的效应来提高作物产量，改善作物品质，同时提高水肥利用效率。本文主要从水肥耦合对葡萄土壤环境和品质的影响方面进行国内外研究动态梳理，从葡萄土壤的水热特性、土壤养分、土壤酶活性及葡萄品质等角度考虑水肥耦合对其的影响。通过文献的整理，为后续水肥耦合对葡萄土壤环境及品质影响的研究提供有力的依据。     

Effects of water infiltration and storage in cultivated soil on surface irrigation

Surface irrigation analysis and design require the knowledge of the variation of the cumulative infiltration water Z (L) (per unit area) into the soil as a function of the infiltration time t (T). The purpose of this study is to evaluate water infiltration and storage under surface irrigation in an alluvial clay soil cultivated with grape yield, and to determine if partially wetted furrow irrigation has more efficient water storage and infiltration than traditional border irrigation. The two irrigation components considered were wet (WT) and dry (DT) treatments, at which water applied when available soil water reached 65% and 50%, and the traditional border irrigation control. Empirical power form equations were obtained for measured advance and recession times along the furrow length during the irrigation stages of advance, storage, depletion and recession. The infiltration (cumulative depth, Z and rate, I) was functioned to opportunity time (t_o) in minute for WT and DT treatments as: Z_WT = 0.528 t_o^0.6, Z_DT = 1.2 t_o^0.501, I_WT = 19 t_o^−0.4, and I_DT = 36 t_o^−0.498. The irrigation efficiency and soil water distribution have been evaluated using linear distribution and relative schedule depth. Coefficient of variation (CV) was 5.2 and 9.5% for WT and DT under furrow irrigation system comparing with 7.8% in border, respectively. Water was deeply percolated as 11.88 and 19.2% for wet and dry furrow treatments, respectively, compared with 12.8% for control, with no deficit in the irrigated area. Partially wetted furrow irrigation had greater water-efficiency and grape yield than both dry furrow and traditional border irrigations, where application efficiency achieved as 88.1% for wet furrow irrigation that achieved high grape fruit yield (30.71 Mg/ha) and water use efficiency 11.9 kg/m³.     

Continuous measurement of plant and soil water status for irrigation scheduling in plum

The usefulness of continuous measurement of soil and plant water status for automated irrigation scheduling was studied in a drip-irrigation experiment on plum (Prunus salicina Black Gold). Two levels of water restriction were imposed at different phenological periods (from pit-hardening to harvest, post-harvest) and compared with a well irrigated control treatment. Soil matrix water potential (_soil) was measured with granular matrix sensors (Watermark); and short-period trunk diameter variation (TDV) was measured with linear variable displacement transformers. The Watermark sensor readings were in reasonable agreement with the irrigation regime and showed a good indication of plant water status across the season (r²=0.62), although they were a better predictor of stem water potential (_stem) in the dry range of _soil. Nonetheless, the most important drawback in their use was the high variability of readings (typical CV of 35–50%). From TDV measurements, maximum daily shrinkage (MDS) and trunk growth rate (TGR) were calculated. Their performance was also compared with _stem, which had the lowest variability (CV of 7%). During most of the fruit growth period, when TGR was minimum, MDS was higher in the less-irrigated treatment than in the control and correlated well (r²=0.89) with _stem. However, after harvest, when TGR was higher, this correlation decreased as the season progressed (r²=0.73–0.52), as did the slope between MDS and _stem, suggesting tissue elasticity changes. Later in the season, TGR was better related to plant water status. These observations indicate some of the difficulties in obtaining reference values useful for irrigation scheduling based exclusively on plant water status measurements.