Uptake and accumulation of emerging contaminants in soil and plant treated with wastewater under real-world environmental conditions in the Al Hayer area (Saudi Arabia)

In arid and semi-arid areas the use of treated wastewater for crop irrigation and other agricultural practices, such as the use of pesticides, increase the number of emerging contaminants (ECs) in crops. Hazards of these practices to human being are largely unknown since there are few studies yet covering a short range of compounds and most of them under non-realistic conditions. This study aims at assessing this problem that will become global soon in an area of Saudi Arabia heavily affected by the reuse of treated wastewater and pesticide in order to ascertain its scale. The novelty of the study relays in the large number of ECs covered and the variety of crops (cabbage, barley, green beans, eggplants, chili, tomato and zucchini) analysed. Extraction procedure developed provided an appropriate extraction yield (up to 50% of the compounds were recovered within a 70-120% range), with good repeatability (relative standard deviations below 20% in most cases) and sensitivity (LOQ < 25 ng g^-1) for the model compounds. Determination by liquid chromatography quadrupole time-of-flight (LC-QqTOF-MS) is able to identify >2000 contaminants. Sixty-four ECs were identified in wastewater but of the sixty-four compounds, six pharmaceuticals (atenolol, caffeine, carbamazepine and its metabolites 10,11-epoxycarbamazepine, gemfibrozil, and naproxen) and seven pesticides (acetamiprid, atrazine deethyl, azoxystrobin, bupirimate, diazinon, malathion, pirimicarb and some of their metabolites) were detected in plants. Furhermore, one metabolite of the ibuprofen (not detected in water or soil), the ibuprofen hexoside was also found in plants. Up to our knowledge, this study demonstrate for the first time the accumulation of ECs in crops irrigated with treated wastewater under real non-controlled environmental conditions.

Energy and environmental performances of hybrid photovoltaic irrigation systems in Mediterranean intensive and super-intensive olive orchards

Over the last decades, traditional olive production has been converted to intensive and super-intensive cultivation systems, characterized by high plant density and irrigation. Although this conversion improves product quality and quantity, it requires a larger amount of energy input. The new contributions in this paper are, first, an analysis of the energy and environmental performance of two commercial-scale high peak-power hybrid photovoltaic irrigation systems (HPVIS) installed at intensive and super-intensive Mediterranean olive orchards; second, an analysis of PV hybrid solutions, comparing PV hybridization with the electric power grid and with diesel generators; and finally, a comparison of the environmental benefits of HPVIS with conventional power sources. Energy and environmental performances were assessed through energy and carbon payback times (EPBT and CPBT). The results show EPBT of 1.98 and 4.58 years and CPBT of 1.86 and 9.16 years for HPVIS in Morocco and Portugal, respectively. Moreover, the HPVIS were able to achieve low emission rates, corresponding to 48 and 103 g CO₂e per kWh generated. The EPBT and CPBT obtained in this study were directly linked with the irrigation schedules of the olive orchards; therefore, weather conditions and irrigation management may modify the energy and environmental performances of HPVIS. The consumption of grid electricity and diesel fuel, before and after the implementation of HPVIS, was also analyzed. The results obtained show fossil energy savings of 67% for the Moroccan farm and 41% for the Portuguese installation. These savings suggest that the energy produced by HPVIS in olive orchards will avoid the emissions of a large amount of greenhouse gas and the exploitation of natural resources associated with fossil fuel production.

Agricultural irrigation of vine crops from desalinated and brackish groundwater under an economic perspective. A case study in Siġġiewi, Malta

Maltese agriculture faces great challenges due to the severe scarcity of water. Sufficient water resources, in quantity and quality, are necessary to cover the demand in the production of wine grape, one of the most important crops in Maltese agriculture. But also, economic efficiency is essential in the grape cultivation. A Cost-Benefit Analysis (CBA) is defined for Maltese vineyards in the Siġġiewi region, considering two irrigation scenarios, irrigation with groundwater or "do-nothing", compared with the "use non-conventional waters" from mixing water from a small desalination plant and groundwater. For the alternative 'mixing desalinated water with groundwater' it is possible to improve water availability and quality for vine crops, while increasing economic benefits for farmer. The results indicate a profitable project from a minimum area of 1 ha, but final benefit is highly dependent on the irrigated surface extension according to water price. Desalination, compared with other type of non-conventional water is considered the best option in this assessment with a small reverse osmosis (RO) desalination plant (120 m³/day) for covering the irrigation needs.

Assessment of nitrate and nitrite levels in treated wastewater, soil, and vegetable crops at the upper reach of Zarqa River in Jordan

The purpose of this study is to examine the impact of treated wastewater irrigation on agricultural soils and vegetables along the upper reach of Zarqa River (Jordan). Multiple samples of reclaimed wastewater, soil pits from farms, and vegetables (spinach, parsley, cabbage cauliflower, radish, and onion) were collected and analyzed for pH, total dissolved solids (TDS), and/or NO₃^- and NO₂^- contents. The average levels of NO₃^- and NO₂^- in treated wastewater samples varied from 167.2 to 209.9 mg/l for NO₃^- and from 80.3 to 106.1 μg/l for NO₂^-. Values of TDS and pH exhibited relatively comparable spatial patterns, with higher values in the downstream channel and lower in the upper reach, adjacent to Al-Samra Wastewater Treatment Plant. The average values of NO₃^- and NO₂^- showed broadly decreasing trends down-gradient towards King Talal Dam. In soil pits, a marginal increase of pH values with depth was noted, whereas TDS showed a remarkable decrease in soil profile by ~ 2 to 3 folds. Concurrently, the levels of NO₃^- and NO₂^- in all soil pits markedly decreased from top to bottom. In vegetables irrigated with treated wastewater, substantially elevated levels of NO₃^- were observed, compared with those irrigated with rainwater, with leafy vegetables demonstrating higher levels than the root crops. Spinach exhibited higher capacity for NO₃^- accumulation (4614.1 mg/kg), while onion showed the lowest content (1722 mg/kg). The highest NO₂^- level was observed in parsley (1.19 mg/kg), and the lowest concentrations were found in cauliflower (0.25 mg/kg). The markedly high accumulation of NO₃^- in vegetables is an indicator of pollution activities around Zarqa River and poses potential health risks to humans when they are consumed.

Assessing climate change impacts on water resources and crop yield: a case study of Varamin plain basin, Iran

This research evaluated climate change impacts on water resources using soil and water assessment tool (SWAT) models under representative concentration pathway scenarios (RCP 2.6, RCP 6, RCP 8.5). First, drought intensity was calculated using the standardized precipitation index (SPI) for the period 1987-2016. Then, the coefficients of precipitation as well as minimum and maximum temperature changes were simulated as SWAT model inputs. The results revealed that temperature will rise in future periods and the precipitation rate will be changed consequently. Then, changes in runoff during periods of 2011-2040, 2041-2070, and 2071-2100 were simulated by introducing downscaled results to SWAT model. The model was calibrated and validated by SWAT calibration and uncertainty procedures (SWAT-CUP). Nash-Sutcliffe (NS) coefficients (0.57 and 0.54) and R² determination coefficients (0.65 and 0.63) were obtained for calibration and validation periods, respectively. The results showed that runoff will rise in fall and spring while it will drop in winter and summer throughout future periods under all three scenarios. Such seasonal shifts in runoff levels result from climate change consequences in the forms of temperature rise, snowmelt, altered precipitation pattern, etc. Future-period evapotranspiration will rise under all three scenarios with a maximum increase in the period 2070-2100 under RCP 8.5 scenario. Additionally, rainfed crop yields will decline without considerable changes in irrigated and horticultural crop yields.

Assessing the performance of different irrigation systems on lettuce (Lactuca sativa L.) in the greenhouse

Lettuce (Lactuca sativa L.) is a very important leafy vegetable in China and is commonly grown using furrow irrigation. In order to improve production efficiency, greenhouse experiments were conducted at Experimental Station, China Agricultural University, Beijing, China using furrow irrigation (FI), micro-sprinkler irrigation (MS), plastic film mulching irrigation (PF) and a combined plastic film mulching-micro-sprinkler irrigation system (PF+MS) to study their effects on soil physical characteristics, water distribution, root morpho-physiological traits, nutrition absorption, lettuce yield and water use efficiency for a spring crop and autumn crop in 2015 (Fig 1). Root length, root surface area, and root density were significantly higher under PF and PF+MS than under FI. Moreover, these traits were higher under MS than under FI but these differences were not significant. The soluble protein, soluble sugar, and Vitamin C content of lettuce decreased in the order PF+MS > PF > MS > FI in both crops. In the spring crop, the biological yield of MS, PF, and PF+MS was 7.22%、36.77%、43.20% higher than FI, respectively. In the spring crop, biological water use efficiency (BWUE) of FI, MS, PF and PF+MS was 20.93, 25.24, 36.81 and 38.54 kg m-3, respectively. The BWUE of MS, PF, and PF+MS was 20.59%, 75.87% and 84.14% higher than FI. Economic water use efficiency (EWUE) of FI, MS, PF and PF+MS was 17.06, 21.31, 31.11 and 32.31 kg m-3, respectively. The EWUE of MS, PF, and PF+MS was 24.91%, 82.36% and 89.39% higher than FI, respectively. The autumn crop achieved a higher WUE than the spring crop. The results suggested that the combined plastic film mulching-micro-sprinkler irrigation was the most suitable irrigation approach for increasing lettuce yield.

Physiological and anatomical studies of two wheat cultivars irrigated with magnetic water under drought stress conditions

The aim of this study was to assess some physiological parameters and anatomical changes in two wheat plant cultivars (Triticum aestivum L. cvs. Sakha 93 and Sids 9) in response to irrigation with magnetized water under two levels of drought stress (field capacity (FC) of 75% and 50%) and the control (FC 100%) in two consecutive winter growing seasons (November 20 to May 5 2014/2015 and 2015/2016). Pot experiments were carried out in a greenhouse in the experimental farm of the Faculty of Agriculture, Menoufia University, Shibin El-Kom, Egypt. A water deficit, particularly at 50% FC, significantly decreased growth and parameter values, above all in Sakha 93, and disrupted most physiological aspects, biochemical constituents and internal structural features of both wheat cultivars. Irrigation with magnetized water alleviated the negative consequences of drought stress on most physiological and biochemical parameters to a variable extent: the whole plant dry weight, total water content, total soluble sugar concentration in leaves, total free amino acids and proline increased by about 32, 12, 17, 27 and 73%, respectively, under 50% FC drought stress in Sids 9 compared to the control. As the levels of drought increased, the grain yield (g/plant) decreased considerably, from about 81% in Sakha 93 at 50% FC to 26% in Sids 9 at 75% FC. The use of magnetic water increased grain yield from 61% in Sakha 93 at 75% FC to about 268% in Sids 9 at 50% FC. Magnetic water also increased the thickness of the flag leaf midvein and lamina, as well as the metaxylem vessel diameter of Sakha 93 by 28.8, 11.7 and 20.0%, respectively, compared to the control. The application of magnetic water increased the growth and the other parameter values studied in both cultivars but above all in Sakha 93, whereas Sids 9 produced more grain yield under all levels of drought stress. As the growth and grain production increased in both cultivars when using magnetic water, this study recommends this type of irrigation for these wheat plants, which are widespread in Egypt.

Characteristics of heavy metals in soils and grains of wheat and maize from farmland irrigated with sewage

The farmland irrigation with the sewage is a common and better pathway to save the resource of groundwater in Northern China. The investigation was conducted in the farmland along the Fuhe River to explore characteristics of heavy metals in soils and grains of wheat and maize from a long-term sewage-irrigated area of Baoding region. The results showed that the topsoil with long-term sewage irrigation accumulated more Cd, Pb, and Hg compared with that of soil irrigated with groundwater and their corresponding natural background values. Cd concentrations in 48% of sewage-irrigated soil samples exceeded the Chinese safety limitation at 0.6 mg/kg, but less Cd accumulated in crop grains and did not pose the potential health risk. On the contrary, Pb levels in soils irrigated with sewage were lower than the safety limitation but Pb concentrations in 24% of wheat grain samples exceeded the Chinese national safety limit. Long-term sewage irrigation did not increase As, Cr, and Ni concentrations in soils or crop grains. The target hazard quotient (THQ) of heavy metals in edible grains of crops was selected to assess their risk to human health. Total THQ values were higher than 1.0 for the wheat samples from sewage-irrigated area and both sewage-irrigated and smelter-impacted areas, and As is the main contributor to the total THQ and posed the potential risk to human health. Therefore, the accumulation of Cd, Pb, Hg, and As in soils and crops in sewage-irrigated area should be monitored continuously to ensure food safety and security.

Climate change adaptation and water saving by innovative irrigation management applied on open field globe artichoke

The setting up of innovative irrigation water management might contribute to the mitigation of negative issues related to climate change. Our hypothesis was that globe artichoke irrigated with a traditionally drip system could be converted to an innovative water management system based on precision irrigation techniques and on evaporative cooling application in order to improve crop physiological status with positive impacts on earliness, total heads yield and water saving. Over two experiments carried out at plot- and field-scale, two irrigation management systems, differing in type and application time, were compared: (i) conventional, and (ii) canopy-cooling. Plant physiological status at a weekly sampling interval and the head atrophy incidence (as the ratio of the total primary heads collected) were monitored. We also recorded and determined heads production, and yield components. In both experiments, throughout the application period of evaporative cooling (three months), canopy-cooling showed the lowest value of leaf temperature and the highest photosynthesis values compared with the conventional one (+3 °C and -30%, respectively). The physiological advantage gained by the crop with evaporative cooling has led to a higher production both in terms of total yield (+30%), and in terms of harvested first order heads that from an economic viewpoint are the most profitable for farmers. At farm-scale, the canopy-cooling treatment resulted in a higher earliness (35 days) and water productivity (+36%) compared with conventional one. Our findings show that by combining evaporative cooling practice with precision irrigation technique the heads yield can be optimized also leading to a relevant water saving (-34%). Moreover, the study proved that canopy-cooling set up might be a winning strategy in order to mitigate climatic changes and heat stress conditions.

Cultivation modes and deficit irrigation strategies to improve 13C carbon isotope, photosynthesis, and winter wheat productivity in semi-arid regions

Determining the effect of ridge-furrow cultivation mode on ¹³C carbon isotope discrimination, photosynthetic capacity, and leaf gas exchange characteristics of winter wheat leaves will help to increase wheat production. To verify these effects of cultivation modes with deficit irrigation will provide scientific basis for determining water-saving strategy. Therefore, a mobile rainproof shelter was used to explore the potential benefit of two cultivation modes: (1) the ridge-furrow (RF) precipitation system and (2) traditional flat planting (TF) with two deficit irrigation levels (150, 75 mm) and three precipitation levels (275 mm, 200 mm, 125 mm) were tested in this study. Plastic film mulching on ridges had significant effects on rainwater collection and improved soil water retention. Analysis of the light-response curve showed that RF2₁₅₀ treatment significantly increased flag leaf net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), transpiration rate (T_r), leaf WUE, and total contents of chlorophyll ab of wheat at flowering stage than that of TF planting. The RF system significantly increases maximum net photosynthetic rate (P_nmax) (16.2%), light saturation points (LSP) (6.7%), and P_n under CO₂-response curves compared to the TF cultivation across the two irrigation and three simulated rainfall levels. The RF system significantly increased Δ¹³C (0.7%) and caused a notable increase in the intercellular to ambient CO₂ concentration ratio (7.6%), dry matter translocation (54.9%), and grain yield plant^-1 (19%) compared to the TF planting. Furthermore, Δ¹³C was significantly positively correlated with P_n, G_s, C_i/C_a, C_i, T_r, P_nmax, LSP, and grain yield. This study suggested that the RF2₁₅₀ treatment was the best water-saving technique because it increased soil water content, Δ¹³C, biomass, grain yield, and leaf WUE.

Anthocyanin accumulation and biosynthesis are modulated by regulated deficit irrigation in Cabernet Sauvignon (Vitis Vinifera L.) grapes and wines

Anthocyanins contents and compositions play an important role in grape berries and wines. Grapevines are widely cultivated in arid and semi-arid areas, and water shortage restricts the development of wine industry. The aim of this work was to gain insight on the effect of regulated deficit irrigation (RDI) on the accumulation and biosynthesis of anthocyanins in Cabernet Sauvignon (Vitis Vinifera L.) grapes and wines. High-performance liquid chromatography (HPLC) was used for anthocyanins profiles analyses and real-time quantitative PCR (qRT-PCR) was used for the genes expressions measurement. The grapevines were treated with 60% (RDI-1), 70% (RDI-2), 80% (RDI-3), 100% (CK, traditional drip irrigation) of their estimated evapotranspiration (ETc) respectively. RDI treatments significantly reduced titration acid and increased pH with higher total soluble solids. RDI-1 treatment increased total anthocyanins contents in berries and wines in both two vintages. RDI-1 and RDI-2 treatments significantly increased the contents of acylated anthocyanins in berries and wines, especially Malvidin-3-acetly-glucoside. RDI treatments significantly increased non-acylated anthocyanins contents in wines, such as Delphinidin-3-gliucoside and Malvidin-3-glucoside. RDI treatments upregulated the expressions of VvPAL, VvC4H, VvCHS, VvF3'H, VvF3'5'H, VvLDOX, and VvOMT in both two vintages. Correlation analysis showed the accumulation of anthocyanins was closely related to the key genes expressions, including VvPAL, VvF3'H, VvF3'5'H etc. The present results provided direct evidence and detailed data to explain that RDI treatments regulated the accumulation of anthocyanins by regulating genes expressions in the anthocyanin synthesis pathway.

Increase in economic efficiency of water use caused by crop structure adjustment in arid areas

The Heihe River is located in the arid zone of northwestern China. In its middle-reach region, irrigation agriculture is well developed. With rapid population growth and expansion of the cultivated land in this region, effective water resource use is vital for the sustainable development of the river basin and the increase of incomes from farming practices. In this study, based on farmer survey data, the input parameters of the CROPWAT model were modified, the water use amount was simulated after deducting the influences of climate, seeds, and irrigation systems, and the variation of economic efficiency of water use (EEWU) induced by crop structure adjustment from 2001 to 2012 was analyzed. The results show that simulations for evapotranspiration of maize based on the CROPWAT model are in accord with the observed data. From 2001 to 2012, due to changes in the regional crop structure, EEWU in the study area increased by about 40%. In the arid areas in northwest China, crop structure adjustment has a huge potential for improving EEWU and increasing incomes from farming practices.

Reducing water use by alternate-furrow irrigation with livestock wastewater reduces antibiotic resistance gene abundance in the rhizosphere but not in the non-rhizosphere

Livestock wastewater is rich in nutrients but may contain antibiotics and antibiotic resistance genes (ARGs). Their discharge to watercourses or soil may result in proliferation of ARGs. Irrigation with wastewater appears to be the most feasible option of disposing of it. One efficient irrigation technology used in arid regions is alternate-furrow irrigation (AFI) by alternately drying part of the plant roots for a prolonged period to physiologically reduce transpiration without compromising yield. However, the extent to which AFI with wastewater influences the concentration of antibiotics and spread of ARGs in soil is poorly understood. The purpose of this paper is to investigate how AFI using swine wastewater alters antibiotic kinetics and ARGs abundance under different irrigation rates, using pepper as the model plant. We examined three AFI treatments using 50%, 65% and 80% of the amount of water employed in sufficient conventional furrow irrigation. Each treatment had a groundwater irrigation control. The results showed that antibiotic concentrations and relative ARGs abundance in the top 20 cm of soil did not increase with the irrigation amount, although they were higher than those in the groundwater-irrigated soils. The relative ARGs abundance in the soil was modulated by irrigation amount and reducing the irrigation amount in AFI reduced ARGs dispersion only in rhizosphere. When the soil moisture was close to field capacity, ARGs were more abundant in rhizosphere than in non-rhizosphere, possibly because the rhizosphere is rich in microbes and increasing antibiotic concentrations due to an increase in irrigation rate favors antibiotic-resistant microbiome in competing for substrates. These, however, were not mirrored in the relative ARGs abundance in the roots. These results have important implications as it revealed that reducing the input of antibiotics and ARGs into soil with AFI does not necessarily reduce ARGs proliferation.

Energy use and economic analysis for wheat production by conservation tillage along with sprinkler irrigation

This study was conducted to investigate the combination of both sprinkler irrigation and conservation tillage in sustainable agriculture for wheat production. To exploit the advantages of the two systems, conventional tillage along with surface irrigation (T₁) and conservation tillage along with sprinkler irrigation (T₂) were compared based on energy indices and economic analysis. The study was carried out for two years of 2012-2013 and 2013-2014 in a semi-arid environment located at the northwest of Iran. Results revealed that the total average energy consumed was 16.36 and 14.07 GJ ha^-1 for T₁ and T₂, respectively. The total energy input components of indirect and non-renewable were 65.3% (54.9%) and 76.0% (62.9%) for T₁ (and T₂). Energy inputs of diesel, nitrogen fertilizer and seeds were prime energy consuming components. In T₂, the sprinkler irrigation was another energy consumption input. The highest net energy gain (109.25 GJ ha^-1), energy use efficiency (5.53), energy productivity (382.00 kg GJ^-1) and energy profitability (8.50) and the lowest specific energy (3.36 MJ kg^-1) were found in T₂. As well as the highest net return (1821.08 US$ ha^-1), a benefit-cost ratio (4.4) and productivity (9.33 kg US$^-1) was obtained in T₂. Therefore, application of conservation tillage along with sprinkler irrigation could be suggested as a promising combination for wheat production in a semi-arid environment.

Effect of treated wastewater irrigation in East Central region of Tunisia (Monastir governorate) on the biochemical and transcriptomic response of earthworms Eisenia andrei

Treated wastewater (TWW) reuse for irrigation has become an excellent way to palliate water scarcity in Mediterranean arid regions. However, the toxicological effects of these effluents on the soil's organisms, especially earthworms, have not been well studied as yet. In this paper, earthworms Eisenia andrei were exposed for 7 days and 14 days to five agricultural soils irrigated with TWW for different periods: 1 year, 8 years, and 20 years. In addition, they were also exposed to soil from one reference site sampled from the Ouardenin perimeter in the Monastir Governorate in Tunisia. The effect on earthworms was assessed at the biochemical level by evaluating for catalase (CAT), glutathione-S-transferase (GST), malondialdehyde accumulation (MDA) and acetylcholinesterase inhibition (AChE). On the other hand, genotoxicity and transcriptomic responses were evaluated using micronuclei test (MNT) and gene expression level of CAT and GST. Moreover, metals uptake by earthworms was analyzed. Results showed that CAT and GST activity in the earthworm increased significantly when they were exposed to soils irrigated with TWW for 1, 8 and 20 years. Furthermore, MDA concentration also increased significantly with the increase in exposure period. However, AChE activity decreased and MNi frequency increased in earthworms after 7 and 14 days of exposure to soils irrigated with TWW for more than a year. The gene expression level of CAT and GST showed a significant variability, thus data are discussed in relation to the studied biomarkers (CAT and GST). These data provide new insights into the effect of toxicity of TWW on the soil's macro fauna, which is strongly affected by the trace elements and other organic compounds accumulated in soils after 20 years of TWW irrigation.

Optimizing irrigation and nitrogen requirements for maize through empirical modeling in semi-arid environment

Uncertainty in future availability of irrigation water and regulation of nutrient amount, management strategies for irrigation and nitrogen (N) are essential to maximize the crop productivity. To study the response of irrigation and N on water productivity and economic return of maize (Zea mays L.) grain yield, an experiment was conducted at Water Management Research Center, University of Agriculture Faisalabad, Pakistan in 2015 and 2016. Treatments included of full and three reduced levels of irrigation, with four rates of N fertilization. An empirical model was developed using observed grain yield for irrigation and N levels. Results from model and economic analysis showed that the N rates of 235, 229, 233, and 210 kg ha^-1 were the most economical optimum N rates to achieve the economic yield of 9321, 8937, 5748, and 3493 kg ha^-1 at 100%, 80%, 60%, and 40% irrigation levels, respectively. Economic optimum N rates were further explored to find out the optimum level of irrigation as a function of the total water applied using a quadratic equation. The results showed that 520 mm is the optimum level of irrigation for the entire growing season in 2015 and 2016. Results also revealed that yield is not significantly affected by reducing the irrigation from full irrigation to 80% of full irrigation. It is concluded from the study that the relationship between irrigation and N can be used for efficient management of irrigation and N and to reduce the losses of N to avoid the economic loss and environmental hazards. The empirical equation can help farmers to optimize irrigation and N to obtain maximum economic return in semi-arid regions with sandy loam soils.

Biochemical and transcriptomic response of earthworms Eisenia andrei exposed to soils irrigated with treated wastewater

In order to ensure better use of treated wastewater (TWW), we investigated the effect of three increasing doses of TWW, 10%, 50%, and 100%, on biochemical and transcriptomic statuses of earthworms Eisenia andrei exposed during 7 and 14 days. The effect of TWW on the oxidative status of E. andrei was observed, but this effect was widely dependent on the dilution degree of TWW. Results showed a significant decrease in the catalase (CAT) activity and an increase in the glutathione-S-transferase (GST) activity, and considerable acetylcholinesterase (AChE) inhibition was recorded after 14 days of exposure. Moreover, malondialdehyde (MDA) accumulation was found to be higher in exposed animals compared to control worms. The gene expression level revealed a significant upregulation of target genes (CAT and GST) during experimentation. These data provided new information about the reuse of TWW and its potential toxicity on soil organisms.

Impact of water and fertilizer management on arsenic bioaccumulation and speciation in rice plants grown under greenhouse conditions

Arsenic (As), a non-threshold class I carcinogen, is a main source of human exposure to inorganic As for billions of people worldwide. Rice is much more effectual in accruing As into its grain and other parts. Therefore, strategies to reduce As accumulation in rice should be adopted. The impact of water [Alternate Wetting and Drying (AWD), incessant flooding (CF)] and fertilizer management [Silicon (Si@ control, 10 and 20 mg/kg soil) and Phosphorus (P@ control, 12.5 and 25.0 mg/kg soil)] on the bioaccumulation of As in rice plants under different As-graded paddy soils (control, 10, 20 mg/kg) using an Australian rice variety (cv. Sherpa) was investigated under greenhouse conditions. Results indicated that, arsenite accounted for >80% of the total inorganic As in pore water and total As concentration declined from 933 μg/L to 177 μg/L with time. AWD irrigation practice with Si fertilization significantly reduced the total As levels in pore water. Arsenic concentration in different rice plant tissues showed significant variations due to water and fertilizer management. Lower concentrations of As in rice grains were observed using AWD (average 93.0 μg/kg) than those observed in CF (average 121 μg/kg) irrigation practice. The addition of Si also significantly (p < 0.03) decreased As uptake by rice plants while adding of P has no significant effect and this is also true for Si and P interaction. AWD irrigation practice with Si fertilization resulted in a reduction of grain As level at around 12%-21%, while grain yield increased by 13%.

Low-frequency electromagnetic treatment of oilfield produced water for reuse in agriculture: effect on water quality, germination, and plant growth

Competing demand for high-quality fresh water for agricultural, industrial, and municipal uses has placed tremendous stress on water resources; irrigating crops with fresh water is expensive and unsustainable. Using unconventional water sources such as oilfield produced water (PW) and treating PW with physical treatment methods such as electromagnetic treatment may overcome water-limitation challenges. A germination experiment was conducted using treated and untreated PW to examine the effect on the germination of iron and clay cowpeas (ICCs) since germination is the stage at which plants are most sensitive to external factors and stresses. The results from the study showed that ICCs germinated when irrigated with higher salinity water that was treated using the electromagnetic technology. A plant growth study was also conducted to assess the effect of electromagnetic treatment of high-salinity PW on the growing ability and crop health of ICCs. A reduction in leaf area expansion rate, the first indicator of salt stress on plants, was observed. After 14 days, plants showed early signs of salt stress such as wilting, lightening in color, and reduction in leaf area. After 28 days, plants watered with higher salinity PW (21,475-42,950 mg/L total dissolved solids) died and plants watered with lower salinity PW (< 21,475 mg/L total dissolved solids) survived but grew smaller than plants irrigated using fresh water. Results from both experiments suggested a potential total dissolved solids limit of ICCs or electromagnetic technology (or both) between 4000 and 10,000 mg/L. The results further suggested that while the electromagnetic technology did not have a strong effect on plant growth, high-salinity water might be treated for reuse in agriculture.

Using phytoremediation by decaying leaves and roots of reed (Phragmites austrates) plant uptake to treat polluted shallow groundwater in Kuwait

Phytoremediation is the use of plants and their associated microorganisms, to remove or degrade biochemically the pollutants from the soil and groundwater environment. It is an emerging technology for water/soil/agricultural remediation, which offers a low-cost flexible technique suitable for use against a number of different types of contaminants in a variety of media. This research illustrates that this technology can be used to reduce the concentration of pollutants in Kuwait shallow groundwater to improve the efficiency of irrigation for greenery purposes. The investigation of this research was carried out through using reed plants in two experiments: First in decaying reed leaves and the second in reed roots. The change in the concentration of the inflow of the polluted groundwater and the outflow of the treated irrigation water was measured in the laboratory for chemical analysis. The two experiments indicated the ability of the reed plants to reduce the concentration of salt ions (Cl, Na, K, and SO₄) by about 66-78%. Roots reduced the total dissolved solid values by 66%, the plants were capable of reducing the concentration of nitrogen compounds significantly, and fluoride was reduced by ≈ 86% while the roots removed the lithium significantly. This research illustrates that the roots of the reed plants are capable to reduce the heavy metals of Cd, Co, Zn, and Fe significantly. The reduction of Al, Cu, and Cr by the roots of the reed plants was 53%, 39%, and 89% respectively. These results provide a preliminary indication that reed plants have the capability to remove pollutants at various levels and that salinity can be reduced considerably to improve irrigation efficiency in Kuwait.

Techno-economic assessment of a multi-effect distillation plant installed for the production of irrigation water in Arica (Chile)

In the context of a regional Chilean project (FIC Taltape project, BIP code 30158422-0), a multi-effect distillation (MED) pilot plant has been built and installed in a small community in the north of Chile (Taltape, Arica) in order to supply treated water for agricultural and domestic purposes. The aim of this paper is to assess the techno-economic feasibility of this system for supplying water with the required quality to the population. The characterization of the feed water and the effluents from the MED pilot plant (distillate and brine), obtained during five months of operation, has been firstly performed. Then, the prediction of the operation of the water treatment system with solar energy has been carried out using a typical meteorological year and the design of a static solar field that cover the thermal energy needs of the water treatment plant. The annual simulations of the MED pilot plant operating with solar energy showed that the water needs can be mostly covered using a static solar thermal field with a total area of 113.2 m², which would generate roughly 46% of the total heat required by the water treatment plant. The technical analysis has been completed with an exhaustive economic assessment. The specific water costs have been determined for the MED pilot plant and the scale factor when the productivity is increased up to 5000 m³/day has been evaluated. The cost of distillated water produced by the MED plant varied from 15.0 USD$/m³ for the 10 m³/day production capacity to 1.25 USD$/m³ when this variable is increased to 5000 m³/day.

Micro-irrigation improves grain yield and resource use efficiency by co-locating the roots and N-fertilizer distribution of winter wheat in the North China Plain

Water use efficiency (WUE) and nitrogen fertilizer use efficiency (NUE) of winter wheat are urgently needed to further improve in the North China Plain (NCP). In this study, a 3-year field experiment was conducted during the 2014-2017 growing seasons to clarify the effect of traditional flood irrigation (TI), surface drip irrigation (DI), and micro-sprinkling irrigation (MSI) on grain yield, WUE, and NUE of winter wheat. Across the 3 years, grain yield of DI and MSI improved by 9.79% and 14.1%, WUE of DI and MSI increased by 12.3% and 17.7%, and NUE of DI and MSI increased by 9.77% and 14.0%, respectively compared with those of TI. Wheat subjected to the micro-irrigation treatments (DI and MSI) had higher chlorophyll content in flag leaves 10 days post-anthesis; this postponed senescence of the flag leaves, which increased dry matter accumulation post-anthesis, and increased 1000-grain weight and grain yield. The micro-irrigation treatments reduced pre-anthesis water consumption but increased post-anthesis water consumption and ensured the water supply in the top soil layer at the critical stage, thus increasing WUE. Root length density (RLD) of TI in the 0-80-cm soil layer was significantly higher than that of micro-irrigation, whereas micro-irrigation had higher RLD than TI below the 80-cm soil layer, which promoted the absorption and utilization of water and nitrogen in deep soil. The micro-irrigation treatments increased total nitrogen accumulation of the plants, reduced soil nitrate nitrogen (NO₃^--N) content at maturity, ensured the nitrogen supply in the top soil layer, thus increasing NUE. Overall, micro-irrigation with water and fertilizer as an integrated pattern significantly improved grain yield, WUE, and NUE of winter wheat in the NCP by co-locating the root, water, and N-fertilizer distribution and reducing NO₃^--N accumulation in deep soil. The best treatment was micro-sprinkling irrigation.

[Effects of deficit irrigation on water-radiation use and yield of Coffea arabica under different shade cultivation modes in dry-hot region]

The yield and quality of Coffea arabica cannot be guaranteed due to irrational irrigation and light management in dry-hot region. To investigate the best coupling mode of irrigation and shade cultivation of C. arabica in dry-hot region, a field experiment was carried out with different irrigation levels and shade cultivation modes. Three levels of irrigation, i.e., full irrigation, light deficit irrigation and severe deficit irrigation, and four modes of shade cultivation, i.e., no shade cultivation (C. arabica monoculture), light shade cultivation (intercropping of four-line C. arabica and a line banana), moderate shade cultivation (intercropping of three-line C. arabica and a line banana) and severe shade cultivation (intercropping of two-line C. arabica and a line banana) were designed to examine the effects of deficit irrigation on growth, photosynthetic characteristics of lea-ves, water-radiation use and yield of C. arabica under the shade of banana trees. The results showed that net photosynthesis rate (P_n), transpiration rate (T_r), stomatal conductance (g_s), leaf water use efficiency (LWUE), leaf radiation use efficiency (LRUE) increased with the increases of irrigation amount, while the intercellular CO₂ concentration (C_i) decreased with the increases of irrigation amount. Compared with full irrigation, light deficit irrigation decreased dry bean yield by 9.4%, severe deficit irrigation decreased dry bean yield and water use efficiency (WUE) by 36.7% and 16.9%, respectively. P_n, T_r, g_s, LWUE first increased and then decreased with the increases of shading degree, with moderate shade cultivation having the maximum increment. Compared with no shade cultivation, light shade cultivation increased dry bean yield and WUE by 13.0% and 12.9%, respectively; moderate shade cultivation increased dry bean yield and WUE by 23.1% and 23.4%, respectively. The dry bean yield, WUE, volume and fresh mass of 100-bean of C. arabica increased in different degrees with the increases of irrigation amount and shading degree, with the largest enhancement of dry bean yield and WUE occurring in full irrigation under moderate shade cultivation_. Soil water content in the same soil depth decreased with the increases of shading degree. Soil water content in the same place increased first and then decreased with the increases of soil la-yer depth in 0-50 cm soil layer. Results of regression analysis showed that LRUE had a significantly negative exponential relation or Logistic-curve variation with photosynthetically active radiation. Therefore, the suitable combination of irrigation treatment and banana shade cultivation mode for C. arabica was full irrigation and moderate shade cultivation, considering the comprehensive benefit of superior quality and high production and high efficiency water-radiation use.

Irrigation options to save water while enhancing export-size fruit and storability of 'Smooth Red' cactus pear

BACKGROUND

A two-year study assessed deficit irrigation options for their effects on water-saving, yield, fruit quality, and postharvest performance of 'Smooth Red' cactus pear. We evaluated: (i) full irrigation (FI), (ii) partial rootzone drying (PRD), (iii) deficit irrigation (DI), and (iv) non-irrigated (NI) treatment as control.

RESULTS

The FI plants had the largest fruit size and the highest yield. PRD and DI plants used irrigation water with the highest efficiency and had the highest water productivity. The NI plants showed the highest water use efficiency in both growing seasons. Compared with FI, the yield was reduced in PRD by 5.5% in 2005 and by 7.8% in 2006. The corresponding reductions for DI were 6.0% and 7.4%, respectively. The NI plants had the lowest percentage of marketable yield. The PRD and DI treatments did not negatively affect fruit quality attributes either at harvest or after storage compared with FI and NI fruits. Fruit water loss tended to be lower in FI, PRD, and DI fruits.

CONCLUSIONS

This study was aimed at obtaining the maximum yield per unit of water applied instead of maximizing the yield per unit of area. We therefore recommend PRD or DI as feasible irrigation options for sustainable production of cactus pear. © 2018 Society of Chemical Industry.

Incidence of bacterial diseases associated with irrigation methods on onions (Allium cepa)

BACKGROUND

In the last decade, diseases of bacterial origin in onions have increased and this has led to significant losses in production. These diseases are currently observed in both the Old and New Worlds. The present study aimed to evaluate whether the irrigation method influences the incidence of diseases of bacterial origin.

RESULTS

In cases where the inoculum was natural, the initial incidence of soft bacterial rot did not manifest in any treatment in the first year, whereas, at the end of the conservation period, all treatments had increased incidences of infection. Sprinkler irrigation (8%) was statistically differentiated from the other treatments, for which the final incidence was similar (4.5%). For all irrigation treatments, the final incidence of bacterial soft rot decreased or remained stable towards the end of the cycle, with the exception of sprinkler irrigation in 2015, which increased.

CONCLUSION

From the results of the present study, it can be inferred that the irrigation method does have an influence on the incidence of diseases of bacterial origin in the post-harvest stage for onions. © 2018 Society of Chemical Industry.

Effects of irrigation with secondary treated wastewater on physicochemical and microbial properties of soil and produce safety in a semi-arid area

Water scarcity is becoming one of the largest problems worldwide. Agricultural reuse of wastewater has been considered a valuable and reliable alternative, alleviating the pressure on freshwater resources in arid and semi-arid regions such as the Middle East. Inadequate microbial quality of treated wastewater is a challenge for developing countries, which limits agricultural reuse of wastewater. This study assessed the impact of irrigation with secondary treated wastewater (STWW) on soil properties as well as the safety of various types of crops as compared with tap water (TW) irrigation through a furrow system. Total and fecal coliforms and Escherichia coli were monitored as indicator bacteria in STWW, irrigated soil and harvested crops. The presence of pathogenic E. coli O157, Salmonella and Shigella was also monitored in all samples using a combination of culture and molecular methods. The microbial quality of wastewater in terms of E. coli concentration (4.18 Log MPN/100 ml) failed to meet the world health organization (WHO) recommendation for irrigation of root and leafy crops (≤103 and ≤ 104E. coli per 100 ml for root and leafy crops, respectively). No significant effects on physicochemical properties of the soil irrigated with STWW was found in comparison with control plots, except for electrical conductivity (EC) and sodium adsorption ratio (SAR), which were slightly higher in STWW soil samples. Although the microbial quality of soil was affected by STWW irrigation, a relatively low concentration of E. coli was detected in soil. No microbial contamination in terms of E. coli was found on harvested maize and onion. E. coli contamination of lettuce and spring onion was found for both irrigation schemes. No STWW, soil or crop samples were found positive for pathogenic bacteria. According to the analyzed parameters, STWW could be safely used as an alternative source for irrigation of root and leafy crops.

Use of autonomous transmission line-type electromagnetic sensors for classification of dry and wet periods at sub-hourly time intervals

Accurate identification of wet and dry weather periods at sub-hourly time intervals is important for the description and control of processes directly influenced by rainfall, such as infiltration into urban drainage systems, purification processes in wastewater treatment plants, or effective irrigation systems. It is also necessary for monitoring and modeling rainfall itself. Traditional instrumentation used to measure rainfall (rain gauges and radars) often fails to detect the transition between dry and wet weather at sufficient spatial and temporal resolution. Opportunistic sensing has become a promising approach in hydrology to overcome these deficits without drastically increasing the cost of measuring campaigns. In this study, we identify dry and wet weather periods using autonomous and inexpensive transmission line-type electromagnetic sensors, primarily intended for soil water content measurement.Four transmission line-type electromagnetic sensors, a tipping bucket rain gauge, and a laser precipitation monitor were installed in an urban catchment for an experimental period of 3 months during the summer. An algorithm for the reliable detection of the onset and end of precipitation episodes was developed for use with the sensors. Our analysis demonstrates that transmission line-type electromagnetic sensors provide results with accuracy similar to, and with five times greater sensitivity than a tipping bucket rain gauge. However, the sensors produced false-negative results more than 1.6% of the time (i.e., 25% of the received rain). Nevertheless, the low specificity of the sensors is not critical when they are used in combination with rain gauges or other sensors that are less prone to falsely detect wet periods.

Mitigation of sodium risk in a sandy agricultural soil by the use of natural zeolites

Na⁺ contamination of irrigation waters represents a global environmental issue for soil structure and plant production. Notwithstanding several techniques for the reduction of Na⁺ have been proposed in recent years, they generally exhibit disadvantages, including low recyclability and relatively high operational/maintenance costs. In this paper, we propose a natural and eco-friendly solution for the reduction of Na⁺ risk in coastal agricultural sandy soil (SS), vulnerable to salinity stress. A series of column leaching experiments have been conducted to assess the influence of Italian zeolite-rich tuff (natural zeolites, NZ) addition to soil (NZSS) on Na⁺ removal, SAR, and CROSS index, under three different salinity scenario. Result showed that the Na⁺ removal efficiency varied between 46.4 and 54.3% in soil amended with NZ, and analogously SAR index was significantly reduced from 7 to up 13 points. SAR and CROSS indexes resulted better correlated in SS rather than NZSS due to the influence of K⁺ released by NZ. In conclusion, soil amendment with NZ represents a natural and eco-friendly solution for increasing sandy soil resilience to Na⁺ risk.

Effect of straw return on soil respiration and NEE of paddy fields under water-saving irrigation

Straw return (SR) and rice water-saving irrigation (WSI) affect the greenhouse gas emission of paddy fields. However, studies on CO₂ exchange between paddy fields and the atmosphere with joint regulation of SR and WSI are few. We conducted a two-year field experiment to investigate the effects of SR on soil respiration and net ecosystem exchange of CO₂ (NEE) in paddy fields under controlled irrigation (CI), which is a typical WSI technique. The rice yields, irrigation water use efficiency, seasonal variations in soil respiration, NEE, and soil organic carbon content were measured. Compared with the control (flooding irrigation and traditional chemical fertilizer), a significant increase in rice yield and irrigation water use efficiency in the paddy fields under CI and SR joint management (CS) was observed. CS increased the soil respiration rate during most of the rice growth stage and increased the net CO₂ absorption rate before approximately 80 days after transplanting; afterward, the pattern reversed. Total CO₂ emissions through soil respiration in CS paddy fields increased by 43.7% and 182% compared with the control in 2014 and 2015, respectively. However, CS also caused an increase in the total net CO₂ absorption by 18.1% and 30.1% in these two years, respectively. The acceleration in the consumption and decomposition of soil organic carbon induced by frequent alternate wet–dry cycles of the CI paddy fields increased the soil respiration and decreased the net CO₂ absorption. SR promoted soil respiration but also improved rice growth, increasing the net CO₂ absorption. The soil organic carbon content of the CS paddy fields after harvesting increased by 23.2% compared with that before transplanting. The present study concluded that joint regulation of WSI and SR is an effective measure for maintaining yield, increasing irrigation water use efficiency, mitigating CO₂ emission, and promoting paddy soil fertility.

Impact of wastewater-irrigation on in-household water contamination. A cohort study among urban farmers in Ahmedabad, India

This cohort study explores the contribution of wastewater irrigation, in the context of WASH (Water, Sanitation, Hygiene), on in-household water contamination among urban farming households in Ahmedabad, India. Drinking water samples of 204 households in four peri-urban farming communities were collected from the point-of-source (PoS) and point-of-use (PoU) of each household four times over the 12-month follow-up period. Next to the quantification of E. coli, three household surveys (baseline, hygiene and farm) were conducted. Additionally, an observational spot-check was undertaken in bi-monthly intervals throughout the follow-up period. Significant positive differences in water quality between PoS and PoU samples were identified in 78% of households. During the monsoon, the peak of contamination, only 6% of households had access to safe drinking water at PoU. The Average Treatment Effect (ATE) of wastewater irrigation indicates an adverse effect on in-household water contamination, larger in effect size than the mitigation effect of access to sanitation or personal hygiene. To control transmission of fecal pathogens, effective barriers are required for wastewater irrigation similar to the necessity of ensuring access to sanitation and practicing adequate hygiene behavior.

Benefits of soil biochar amendments to tomato growth under saline water irrigation

Biochar amendments have been used in agriculture to improve soil fertility and enhance crop productivity. A greenhouse experiment was conducted to test the hypothesis that biochar amendment could also enhance the productivity of salt-affected soils. The trial was conducted over two consecutive growing seasons to investigate the effect of biochar amendment (four application rates as: B1 = 0%, B2 = 2%, B3 = 4%, and B4 = 8% by mass of soil) on yield and quality of tomatoes grown in a silt loam soil using non-saline water (I0 = 0.7 dS m-1) and saline water (I1 = 1 dS m-1; I2 = 3 dS m-1) irrigation. Furthermore, the study investigated the mechanism by which biochar addresses the salt stress on plant. The results showed that soil productivity as indicated by the vegetative growth and tomato yield components was adversely and significantly affected by saline water irrigation (P < 0.05). Tomato yield decreased from 689 ± 35.6 to 533 ± 79.0 g per plant as salinity of irrigation water increased from I0 to I2. Then, biochar amendment increased vegetative growth, yield, and quality parameters under saline irrigation water regimes, and ameliorated the salt stresses on crop growth. The highest (8.73 ± 0.15 and 4.10 ± 0.82 g kg-1) and the lowest (8.33 ± 0.08 and 2.42 ± 0.76 g kg-1) values of soil pH and soil organic matter were measured at B4I0 and B1I2 treatments, respectively. Also, the highest rate of biochar amendment combining with non-saline water irrigation (B4I0) produced tomato with the highest plant photosynthetic (17.08 ± 0.19 μmol m-2 s-1) and transpiration rate (8.16 ± 0.18 mmol H2O m-2 s-1). Mechanically, biochar amendment reduced transient sodium ions by adsorption and released mineral nutrients such as potassium, calcium, and magnesium into the soil solution. Therefore, biochar amendments have the potential in ameliorating salt stress and enhancing tomato production.

Quantification of nitrate sources and fates in rivers in an irrigated agricultural area using environmental isotopes and a Bayesian isotope mixing model

Nitrate (NO₃^-) pollution in rivers caused by intensive human activities is becoming a serious problem in irrigated agricultural areas. To identify NO₃^- sources and reveal the impact of irrigation projects on NO₃^- pollution in rivers, the hydrochemistry and isotopes of irrigation water from the Yellow River (IW) and river water (RW), and potential source samples were analyzed. The mean NO₃^- concentrations in the IW and RW were 24.4 mg/L and 49.9 mg/L, respectively. Approximately 45.2% of RW samples (n = 31) exceeded the Chinese drinking water standard for NO₃^- (45 mg/L). The δ¹⁵N and δ¹⁸O values, combined with the Cl^-/Na⁺, SO₄^2-/Ca²⁺ ratio distributions, indicate that the NO₃^- in the RW mainly originated from chemical fertilizers, manure and sewage. A Bayesian model showed that manure and sewage contributed the most to the overall NO₃^- levels of the IW. In the RW, chemical fertilizers and IW contributed the most to the overall NO₃^- levels. The mean nitrate contribution to the RW from the combination of chemical fertilizers and IW is estimated to be 51.6%. Nitrogen from manure and sewage, soil N and precipitation also contributed. The NO₃^- pollution in rivers was largely influenced by the irrigation regime, with a large amount of nitrogen in chemical fertilizer lost because of low utilization efficiency and subsequent transfer, via irrigation runoff, into the rivers. This study suggests that with a detailed assessment of the sources and fate of NO₃^-, effective reduction strategies and better management practices can be implemented to control NO₃^- pollution in rivers.

Nitrogen leaching losses following biogas slurry irrigation to purple soil of the Three Gorges Reservoir Area

Ammonium (NH₄⁺) in biogas slurries is readily nitrified into very mobile soil nitrate (NO₃^-) to promote nitrogen (N) leaching concerning which a few studies, however, have been reported. These slurries are regularly applied through irrigation to purple soil in the Three Gorges Reservoir Area, and therefore we explored the consequent N leaching there with a plot experiment. Biogas slurry irrigation was carried out with nitrogen application rates of 0, 48, 144, 240, 336, and 480 kg N/ha. As a result, the last two rates have triggered N leaching being detrimental to groundwater safety. In addition, N leaching was negatively correlated with soil microbial biomass, diversity, and respiration, indicating a potential technique to prevent it with soil heterotrophs activated by increased ratios of carbon to nitrogen (C/N) in biogas slurries.

Tracking enteric viruses in green vegetables from central Argentina: potential association with viral contamination of irrigation waters

Consumption of green vegetable products is commonly viewed as a potential risk factor for infection with enteric viruses. The link between vegetable crops and fecally contaminated irrigation water establishes an environmental scenario that can result in a risk to human health. The aim of this work was to analyze the enteric viral quality in leafy green vegetables from Córdoba (Argentina) and its potential association with viral contamination of irrigation waters. During July-December 2012, vegetables were collected from peri-urban green farms (n = 19) and its corresponding urban river irrigation waters (n = 12). Also, urban sewage samples (n = 6) were collected to analyze the viral variants circulating in the community. Viruses were eluted and concentrated by polyethylene glycol precipitation and then were subject to Reverse Transcription Polymerase Chain Reaction to assess the genome presence of norovirus, rotavirus and human astrovirus. The concentrates were also inoculated in HEp-2 (Human Epidermoid carcinoma strain #2) cells to monitor the occurrence of infective enterovirus. The frequency of detection of the viral groups in sewage, irrigation water and crops was: norovirus 100%, 67% and 58%, rotavirus 100%, 75% and 5%, astrovirus 83%, 75% and 32% and infective enterovirus 50%, 33% and 79%, respectively. A similar profile in sewage, irrigation water and green vegetables was observed for norovirus genogroups (I and II) distribution as well as for rotavirus and astrovirus G-types. These results provide the first data for Argentina pointing out that green leafy vegetables are contaminated with a broad range of enteric viruses and that the irrigation water would be a source of contamination. The presence of viral genomes and infective particles in food that in general suffer minimal treatment before consumption underlines that green crops can act as potential sources of enteric virus transmission. Public intervention in the use of the river waters as irrigation source is needed.

Irrigation has more influence than fertilization on leaching water quality and the potential environmental risk in excessively fertilized vegetable soils

Excessive fertilization is a common agricultural practice that often negatively influence soil and environmental quality in intensive vegetable production systems in China. To reduce negative effects of excessive fertilization, current studies generally focused on fertilizer management but not irrigation. In this study, we investigated the effects of fertilization and irrigation on soil properties, leaching water characteristics, plant growth, cucumber yield, irrigation water use efficiency (IWUE) and partial factor productivity of nitrogen (PFP_N) in a double cropping system. The treatments included (i) conventional irrigation with conventional N fertilization (IcNc), (ii) optimal irrigation with conventional N fertilization (IoNc), (iii) conventional irrigation with optimal N fertilization (IcNo), and (iv) optimal irrigation with optimal N fertilization (IoNo). In general, fertilization merely influenced concentrations of nitrate (NO₃^-), phosphorus (P) and potassium (K), but did not affect most leaching water characteristics. In contrast, irrigation influenced pH, EC and concentrations of P, K, Ca, Mg, Na and Cu. Cumulative leached amounts of NO₃^-, P, K, Ca, Mg, Na, Fe, Cu and Zn were significantly decreased by optimal irrigation as compared to conventional irrigation under same fertilization conditions, but not by optimal fertilization as compared to conventional fertilization under same irrigation conditions. The leachate volume was strongly positively correlated with cumulative leached amounts of all tested elements, and these relationships were obviously influenced by irrigation but not fertilization. The IoNo treatment significantly increased both IWUE and PFP_N as compared to the IcNc treatment. However, the IcNo treatment only enhanced PFP_N, while the IoNc treatment improved IWUE, when compared to the IcNc treatment. Our results suggested that irrigation has more influence than fertilization on leaching water quality and that the optimal irrigation combined with optimal fertilization was efficient in reducing the potential environmental risk caused by excessive fertilization in intensive vegetable production systems.

Stable isotope measurements show increases in corn water use efficiency under deficit irrigation

Deficit irrigation has usually improved crop water use efficiency (WUE), but there are still gaps in our understanding of the mechanisms. Four irrigation treatments were a conventional furrow irrigation (CFI), border irrigation (BI), alternate furrow irrigation (AFI), and an AFI(M/2) (the amount of irrigation was 50% of the AFI). The volume of irrigation water applied were nearly the same for CFI, BI, and AFI. The isotope (δ18O and δD) method was used to quantify corn root water uptake (RWU) during 2013-2014. Compared to CFI and BI, corn yield and WUE were 17.0-30.2% and 13.3-33.8% higher in AFI, respectively. No significant yield reduction were observed between AFI and AFI(M/2). Corn RWU was more from deeper soil with increasing growth stage for AFI(M/2), AFI, and CFI, but from shallower depth for BI. The depth for RWU varied in the order of AFI(M/2)  > AFI > CFI > BI. The maximum root density was in the depth of 40-80 cm at the growing stage in AFI, and 4-26% more water was extracted from the wetter and deeper root zones. The WUE increased under deficit irrigation, and stimulated the root growth with attendant decreases in water loss to deep percolation.

Spatio-temporal distribution and chemical characterization of groundwater quality of a wastewater irrigated system: A case study

Wastewater irrigation is a common livelihood practice in many parts of the developing world. With the continuous irrigation supply, groundwater systems in these regions perceive adverse impacts due to inadequate infrastructure to treat the wastewater. The current study area, Musi River irrigation system, is one such case study located in the peri-urban Hyderabad of South India. The Musi River water, which is used for irrigation, is composed of untreated and secondary treated wastewater from Hyderabad city. Kachiwani Singaram micro-watershed in the peri-urban Hyderabad is practicing wastewater irrigation for the last 40 years. The current quality of (untreated) wastewater used for irrigation is expected to have adverse impacts on the local aquifers, but detailed investigations are lacking. To elucidate the groundwater quality dynamics and seasonality of the wastewater irrigation impacts on the peri-urban agricultural system, we analyzed the groundwater quality on a monthly basis for one hydrological year in the wastewater and groundwater irrigated areas, which exist next to each other. The spatio-temporal variability of groundwater quality in the watershed was analyzed with respect to wastewater irrigation and seasonality using multivariate statistical analysis, multi-way modeling and self-organizing maps. This study indicates the significance of combining various statistical techniques for detailed evaluation of the groundwater processes in a wastewater irrigated agricultural system. The results suggest that concentrations of the major ionic substances increase after the monsoon season, especially in wastewater irrigated areas. Multi-way modeling identified the major polluted groundwaters to come from the wastewater irrigated parts of the watershed. Clusters of chemical variables identified by using self-organizing maps indicate that groundwater pollution is highly impacted by mineral interactions and long-term wastewater irrigation. The study recommends regular monitoring of water resources and development of sustainable management strategies to mitigate the aquifer pollution in wastewater irrigation systems.

Irrigating Lettuce with Wastewater Effluent: Does Disinfection with Chlorine Dioxide Inactivate Viruses?

Reclaimed water obtained from urban wastewater is currently being used as irrigation water in water-scarce regions in Spain. However, wastewater can contain enteric viruses that water reclamation treatment cannot remove or inactivate completely. In the present study, greenhouse-grown baby lettuce ( L.) was irrigated with secondary treatment effluent from a wastewater treatment plant untreated and treated using chlorine dioxide (ClO). The effect of ClO treatment on the physicochemical characteristics and the presence of enteric viruses in irrigation water and lettuce was assessed. The presence of human noroviruses genogroups I and II (NoV GI and NoV GII), and human astroviruses (HAstV), was analyzed by real-time polymerase chain reaction (RT-qPCR). Additionally, to check for the loss of infectivity induced by the disinfection treatment, positive samples were re-analyzed after pretreatment with the intercalating dye PMAxx before RNA extraction and RT-qPCR. There were no significant differences in the proportion of positive samples and the concentration of enteric viruses between treated and untreated reclaimed water without PMAxx pretreatment ( > 0.05). A significantly lower concentration of NoV GI was detected in ClO-treated water when samples were pretreated with PMAxx ( < 0.05), indicating that inactivation was due to the disinfection treatment. Laboratory-scale validation tests indicated the suitability of PMAxx-RT-qPCR for discrimination between potentially infectious and ClO-damaged viruses. Although the applied ClO treatment was not able to significantly reduce the enteric virus load of the secondary effluent from the wastewater treatment plant, none of the lettuce samples analyzed ( = 36) was positive for the presence of NoV or HAstV.

Effects of Low-Grade Weirs on Soil Microbial Communities in Agricultural Drainage Ditches

Agricultural fertilizer application throughout the Mississippi River basin has been identified as a major source of N pollution to the Gulf of Mexico. Using best management practices, such as low-grade weirs, has been identified as a potential solution to mitigate nutrient loads in agricultural runoff. This study assessed impacts of weir implementation in four agricultural drainage ditches (three with weirs and one control site) in the Mississippi Delta. Soil samples collected from field locations in spring 2013 were analyzed for denitrifier abundance using genes (16s ribosomal RNA [rRNA] genes, , , and ) via quantitative polymerase chain reaction (qPCR), microbial community profiles via terminal-restriction fragment length polymorphism (T-RFLP) of 16s rRNA genes, soil parameters (C, N, and moisture), and vegetation presence at sample locations. Gene quantification was successful, except for , which was found below detection limits (5000 gene copies g soil). Distance from weirs was negatively correlated with 16S rRNA genes and soil moisture, and soil moisture was positively correlated with 16s rRNA and S gene abundance. Results of empirical Bayesian kriging did not exhibit obvious patterns of microbial diversity in relation to weir proximity. Preliminary assessment of seasonal trends showed genes 16s rRNA and , soil N, and mean T-RF values to be greater in fall than in spring. Results highlight that weirs had no direct impact on microbial diversity or denitrification functional gene abundance. Correlations between microbial measures and environmental parameters suggest that adequate management of N runoff from agricultural landscapes will require ecological engineering beyond weirs to optimize N mitigation.

Migration and health risks of nonylphenol and bisphenol a in soil-winter wheat systems with long-term reclaimed water irrigation

Reclaimed water reuse has become an important means of alleviating agricultural water shortage worldwide. However, the presence of endocrine disrupters has roused up considerable attention. Barrel test in farmland was conducted to investigate the migration of nonylphenol (NP) and bisphenol A (BPA) in soil-winter wheat system simulating reclaimed water irrigation. Additionally, the health risks on humans were assessed based on US EPA risk assessment model. The migration of NP and BPA decreased from the soil to the winter wheat; the biological concentration factors (BCFs) of NP and BPA in roots, stems, leaves, and grains all decreased with their added concentrations in soils. The BCFs of NP and BPA in roots were greatest (0.60-5.80 and 0.063-1.45, respectively). The average BCFs of NP and BPA in winter wheat showed negative exponential relations to their concentrations in soil. The amounts of NP and BPA in soil-winter wheat system accounted for 8.99-28.24% and 2.35-4.95%, respectively, of the initial amounts added into the soils. The hazard quotient (HQ) for children and adults ranged between 10^-6 and 1, so carcinogenic risks could be induced by ingesting winter wheat grains under long-term reclaimed water irrigation.

Contaminations of Soil and Two Capsicum annuum Generations Irrigated by Reused Urban Wastewater Treated by Different Reed Beds

Background: In order to save potable water, this study aims to evaluate the contamination of soil and Capsicum annuum L. (chilli) watered with urban wastewater (sewage) pre-treated by various wetland systems. Methods: The appropriateness of wetland outflow for irrigation when applying reused wastewater with high contamination of minerals and pathogens was assessed. The impact of wastewaters pre-treated by various wetlands on soil and harvest was tested in terms of mineral and biological contamination risk. Results: The wetlands met the standards for irrigation water for most water quality variables. However, the thresholds for key water quality parameters were significantly (p < 0.05) exceeded. The highest values for total coliforms, ammonium-nitrogen, phosphorus and potassium were 157,072 CFU/100 mL, 8.5 mg/L, 5.0 mg/L, and 7.0 mg/L, respectively. The harvest was moderately polluted only by zinc according to vegetable quality standards (threshold of 50 mg/kg). Zinc concentrations for Filters 2, 4, 6, 7 and 8 were 35.8, 60.6, 65.1, 65.5 and 53.2 mg/kg, respectively. No bacterial contamination was detected. Conclusions: Treatment of domestic wastewater applying constructed wetlands and subsequent recycling of the treated wastewater for irrigation of crops is a good substitute to the traditional application of drinking water for irrigation purposes.

NMR-Based Metabolomics Approach To Study the Influence of Different Conditions of Water Irrigation and Greenhouse Ventilation on Zucchini Crops

This study describes the approach of ¹H NMR metabolomic profiling for the differentiation of zucchini produced under different conditions of water irrigation (desalinated seawater -0.397 dS/m, 0.52 €/m³ vs groundwater -2.36 dS/m, 0.29 €/m³) and ventilation (surface area of the vent openings/greenhouse area was 15.0% for one sector and 9.8% for the other). Overall, 72 extracts of zucchini ( Cucubirta pepo L. cv Victoria) under four different conditions were regularly analyzed during the spring-summer cycle from April to July 2017. We have found that zucchini plants irrigated with desalinated seawater increased the zucchini production yield, presented fruits with higher concentration of glucose, fructose, and vitamin B3, and displayed an increased antioxidant activity. On the contrary, plant groundwater irrigation produced the increment of sucrose level that could rise the sweetness perception of the fruits. Finally, the ventilation variable produced a higher concentration of trigonelline, histidine, and phenylalanine but only on those zucchinis irrigated with groundwater.

Arsenic effects on some photophysical parameters of Cichorium intybus under different radiation and water irrigation regimes

The presence of arsenic (As) in groundwater is a major problem in several parts of Latin America. In the present work, non-destructive approaches to monitor the effects of As on plants of Cichorium intybus, an herbaceous Asteraceae, were explored. In this sense, the effects of As at different levels of water and radiation were evaluated on these crops. Plants were grown in a greenhouse, watered daily with As solutions and exposed to different water and/or light conditions for four months, using a three-factor (As, water, radiation) and two-level resource (As vs non As, field capacity vs half-field capacity condition, light vs shade condition) factorial design. The parameters most affected by this treatment were the area under the first derivative of the reflectance spectrum in the blue region, chlorophyll concentration, the Fred/Ffar-red fluorescence ratio and the quantum yield for the photophysical decay. These changes indicated the ability of this plant species to be a biomonitor for the presence of arsenic in irrigation water. Interestingly, it was further proved in this work that the biomonitoring capacity was enhanced in the presence of sunlight.

Long-Distance Spread of Verticillium dahliae Through Rivers and Irrigation Systems

Verticillium dahliae Kleb. is a soilborne pathogen causing Verticillium wilt disease on several hosts. The pathogen survival structure (i.e., microsclerotia) can be efficiently spread by different dispersal methods. In the present study, the medium to long dispersal spread of the pathogen through rivers and irrigation canals was investigated. Samples of sediments (n = 29) were gathered from eight Lebanese rivers and three regional irrigation canals, in addition to samples of soil particles and plant residues (n = 14) from irrigation filters in commercial orchards. Specific conventional and real-time nested polymerase chain reaction assays detected the pathogen in six rivers-Al Kabir, Al Bared, Litani, Al Awali, Ostwan, and Litani South-and in all sampled canals-Ostwan, Al Bared, and Litani Canal 900. Starting DNA quantities ranged from 0.2 pg to 21.318 ng and an inoculum density, determined by a traditional plating method, varied between nondetectable and 0.2 microsclerotia/g. Viable V. dahliae microsclerotia were also found in residues collected from mesh-type irrigation filters of five commercial orchards. This study confirms that water is an important inoculum source of V. dahliae, being involved in the efficient spread of microsclerotia in Lebanese agricultural areas.

Investigating the bacterial community and amoebae population in rural domestic wastewater reclamation for irrigation

Reclamation of domestic wastewater for agricultural irrigation is viewed as a sustainable option to create an alternative water source and address water scarcity. Free-living amoebae (FLA), which are amphizoic protozoa, are widely distributed in various environmental sources. The FLA could cause considerable environmental and health risks. However, little information is available on the risk of these protozoa. In this study, we evaluated the feasibility using rural domestic wastewater for agricultural irrigation, and analyzed dynamic changes of the microbial community structure and FLA populations in raw and treated wastewater, as well as the phyllosphere and rhizosphere of lettuce production sites that were irrigated with different water sources. The bacterial community dynamics were analyzed by terminal restriction fragment length polymorphism (T-RFLP). The bacterial community structures in the influent were similar to that in the effluent, while in some cases relative abundances varied significantly. The populations of Acanthamoeba spp. and Hartmannella vermiformis in the anaerobically treated wastewater were significantly higher than in the raw wastewater. The vegetables could harbor diverse amoebae, and the abundances of Acanthamoeba spp. and H. vermiformis in the rhizosphere were significantly higher than in the phyllosphere. Accordingly, our studies show insight into the distribution and dissemination of amoebae in wastewater treatment and irrigation practices.

SWAT-MODSIM-PSO optimization of multi-crop planning in the Karkheh River Basin, Iran, under the impacts of climate change

Agriculture is one of the environmental/economic sectors that may adversely be affected by climate change, especially, in already nowadays water-scarce regions, like the Middle East. One way to cope with future changes in absolute as well as seasonal (irrigation) water amounts can be the adaptation of the agricultural crop pattern in a region, i.e. by planting crops which still provide high yields and so economic benefits to farmers under such varying climate conditions. To do this properly, the whole cascade starting from climate change, effects on hydrology and surface water availability, subsequent effects on crop yield, agricultural areas available, and, finally, economic value of a multi-crop cultivation pattern must be known. To that avail, a complex coupled simulation-optimization tool SWAT-LINGO-MODSIM-PSO (SLMP) has been developed here and used to find the future optimum cultivation area of crops for the maximization of the economic benefits in five irrigation-fed agricultural plains in the south of the Karkheh River Basin (KRB) southwest Iran. Starting with the SWAT distributed hydrological model, the KR-streamflow as well as the inflow into the Karkheh-reservoir, as the major storage of irrigation water, is calibrated and validated, based on 1985-2004 observed discharge data. In the subsequent step, the SWAT-predicted streamflow is fed into the MODSIM river basin Decision Support System to simulate and optimize the water allocation between different water users (agricultural, environmental, municipal and industrial) under standard operating policy (SOP) rules. The final step is the maximization of the economic benefit in the five agricultural plains through constrained PSO (particle swarm optimization) by adjusting the cultivation areas (decision variables) of different crops (wheat, barley, maize and "others"), taking into account their specific prizes and optimal crop yields under water deficiency, with the latter computed in the LINGO-sub-optimization module embedded in the SLMP-tool. For the optimization of the agricultural benefits in the KRB in the near future (2038-2060), quantile-mapping (QM) bias-corrected downscaled predictors for daily precipitation and temperatures of the HadGEM2-ES GCM-model under RCP4.5- and RCP8.5-emission scenarios are used as climate drivers in the streamflow- and crop yield simulations of the SWAT-model, leading to corresponding changes in the final outcome (economic benefit) of the SLMP-tool. In fact, whereas for the historical period (1985-2004) a total annual benefit of 94.2 million US$ for all multi-crop areas in KRB is computed, there is a decrease to 88.3 million US$ and 72.1 million US$ for RCP4.5 and RCP8.5, respectively, in the near future (2038-2060) prediction period. In fact, this future income decrease is due to a substantial shift from cultivation areas devoted nowadays to high-price wheat and barley in the winter season to low-price maize-covered areas in the future summers, owing to a future seasonal change of SWAT-predicted irrigation water available, i.e. less in the winter and more in the summer.

Ridge-furrow mulched with plastic film improves the anti-oxidative defence system and photosynthesis in leaves of winter wheat under deficit irrigation

In semi-arid areas of China, the ridge-furrow mulched with plastic film (RF) cultivation system is a common water-saving agricultural technique where the shortage of water resources has become a serious problem. Therefore, we aimed to explore whether this cultivation is actually an improvement over the traditional flat planting (TF) method while testing two deficit irrigation (150, 75 mm) levels to grow winter wheat. Furthermore, we examined the responses of the anti-oxidative defence system and photosynthetic capacity of winter wheat flag leaves under three simulated rainfall (275, 200 and 125 mm) conditions. The results showed that the RF system with 150 mm deficit irrigation and 200 mm simulated rainfall condition (RF2₁₅₀) treatment raised soil water content (%) at the jointing and flowering stages and achieved higher net photosynthesis rates (Pn) in flag leaves. Furthermore, such improvements were due to the reduction of malondialdehyde (MDA) content and oxidative damage during different growth stages of winter wheat. The RF2₁₅₀ treatment significantly increased the activities of superoxide dismutase (SOD); peroxidise (POD), catalase (CAT) and ascorbate peroxidase (APX) and the content of soluble protein (SP) during different growth stages of winter wheat. Furthermore, RF2₁₅₀ treatment attained the highest value at the flowering stage, while also exhibiting significant declines in contents of proline, MDA, H₂O₂ and O₂ in flag leaves. The higher free H₂O₂ and O₂ scavenging capacity and better anti-oxidative enzyme activities under the RF2₁₅₀ treatment were due to the lower level of lipid peroxidation, which effectively protected the photosynthetic machinery. The net photosynthetic rate of flag leaves was positively correlated with SOD, POD, CAT, APX and SP activities, and negatively correlated with proline, MDA, H₂O₂ and O₂ contents. We concluded that the RF2₁₅₀ treatment was the better water-saving management strategy because it significantly delayed flag leaf senescence and caused the increases in SWC, WUE, Pn, antioxidant enzyme activities and grain yield of winter wheat grown in semi-arid regions of China.

Influence of composted poultry manure and irrigation regimes on some morpho-physiology parameters of maize under semiarid environments

Poultry manure (PM), a rich source for crop nutrients, is produced in ample quantities worldwide. It provides necessary nutrient to soil and has a potential to improve plant water holding availability under semiarid environment. The effect of composted poultry manure (CPM) and irrigation regimes on morpho-physiology of selective maize (Zea mays L.) hybrids (H₁ = drought tolerant, H₂ = drought sensitive) was investigated in this study. Two field experiments were conducted during 2010 and 2011 under randomized complete block design with split split-plot arrangements and three replications of each treatment. Irrigation regimes (I₁ = 300, I₂ = 450, I₃ = 600 mm) were kept in main plots; the two maize hybrids (H₁ and H₂) in sub-plots and nutrient levels (L₁ = recommended rate of NPK (control), L₂ = 8 t ha^-1 CPM, L₃ = 10 t ha^-1 CPM, and L₄ = 12 t ha^-1 CPM) were arranged in sub sub-plots. The drought tolerant hybrid showed best growth under all treatments. Results revealed that maximum leaf area index (LAI) was recorded with the application of the recommended dose of NPK. Low irrigation regimes (I₁ and I₂) highly significantly (P < 0.01) reduced the photosynthesis and transpiration rate in both hybrids while application of 12 t ha^-1 CPM was able to partially alleviate the effect of water stress on these parameters. Resultantly, the application of 12 t ha^-1 CPM enhanced the plant growth and increased grain yield (21%; 4.17 vs 5.27) under limited water availability (I₂L₄) as compared to the recommended dose of NPK (I₂L₁). However, the nutrient application under control treatment had maximum grain yield. Therefore, shortage of water for maize production might be partially alleviated by the application of 12 t ha^-1 CPM.