Questions related to the safety of alternative water sources, such as recycled water or reclaimed water (including grey water, produced water, return flows, and recycled wastewater), for produce production have been largely un-explored at the detail warranted for protection of public health. Additionally, recent outbreaks of Escherichia coli (E. coli) in fresh produce, in which agricultural water was suspected as the source, coupled with heightened media coverage, have elevated fruit and vegetable safety into the forefront of public attention. Exacerbating these concerns, new Federal regulations released by the U.S. Food and Drug Administration (FDA) as part of implementation of the FDA Food Safety Modernization Act (FSMA), require testing of agricultural water quality for generic E. coli. Here, we present a review of water quality criteria – including surface water, groundwater recreational water, and water reuse – in an attempt to better understand implications of new FDA regulations on irrigated produce. In addition, a Quantitative Microbial Risk Assessment (QMRA) was conducted to estimate risks from pathogen contamination of food crops eaten fresh under the context of FDA regulations to provide perspective on current water reuse regulations across the country. Results indicate that irrigation water containing 126 CFU/100 mL of E. coli correspond to a risk of GI illness (diarrhea) of 9 cases in 100,000,000 persons (a 0.000009% risk) for subsurface irrigation, 1.1 cases in 100,000 persons (a 0.0011% risk) for furrow irrigation, and 1.1 cases in 1000 persons (a 0.11% risk) for sprinkler irrigation of lettuce. In comparison to metrics in states that currently regulate the use of recycled water for irrigation of food crops eaten fresh, the FDA FSMA water quality metrics are less stringent and therefore the use of recycled water presents a reduced risk to consumers than the FDA regulations. These findings, while limited to a one-time exposure event of lettuce irrigated with water meeting FSMA water quality regulations, highlight the need for additional assessments to determine if the scientific-basis of the regulation is protective of public health.

Sustainable agricultural intensification requires irrigation methods and strategies to minimize yield penalties while optimizing water, land and energy use efficiencies. We assessed, from a silo-based and integrated water-energy-food (WEF) nexus perspective, the performance of irrigation technologies in different agro-climatic regions. Secondary to this, we assessed the impact of adopting systematic approaches such as the WEF nexus on improving efficiency in irrigated agriculture through irrigation modernization. The evidence-based perspectives of silo-based performances individually considered the metrics of yield (Y), water use efficiency (WUE), and energy productivity (EP). The WEF nexus approach applied sustainability polygons to integrate the three metrics into a nexus index representing the holistic performance of the irrigation technologies. Silo-based performance in temperate regions suggests net gains for WUE (+1.10 kg m-3 ) and Y (+6.29 ton ha-1 ) when transitioning from furrow to sprinkler irrigation, with a net loss in EP (-3.82 ton MJ-1 ). There is potential for a net loss on EP (-3.33 ton MJ-1 ) when transitioning from furrow to drip system in temperate regions. The best performance of irrigation technologies in dry regions in water, energy and food silos was achieved by sprinkler, drip and furrow irrigation systems, respectively. Thus, appraising irrigation technologies from a silos perspective promotes individual silos, which renders an unsustainable picture of the performance of irrigation systems. The integrative WEF nexus approach successfully highlighted the trade-offs and synergies in the nexus of water, energy and food in irrigated agriculture. Drip irrigation led all irrigation technologies in WEF nexus performance in dry (21.44 unit2 ), tropical (23.98 unit2 ), and temperate regions (47.28 unit2 ). Overall, the irrigation modernization pathway to drip technology from either furrow or sprinkler systems improves irrigated agriculture’s WEF nexus performance in all three regions for more crop per drop per joule per hectare under climate change. This can promote inclusive and sustainable irrigation development within the planetary boundaries.

Food processing waste waters at two irrigated land disposal sites and subsurface waters (perched and ground waters) were monitored at daily to monthly intervals over one annual cycle of production. Soil profiles were sampled to depths up to 6.6 m in the early fall. Yearly inputs were calculated at 487 kg/ha total N (Kjeldahl plus NO³-N) and 101 kg/ha soluble PO₄-P (orthophosphate) from cannery wastes at site 1. Estimates for milk wastes at site 2 were 562 kg/ha total N and 522 kg/ha PO₄-P. The range for NO₃-N in subsurface waters was 7 to 16 ppm at site 1 (perched water at 1.5 m) and 2 to 41 ppm at site 2 (ground water at 0.9 m). Maximum concentrations, found in summer, were essentially the same as the average for total N in the input wastes (16 ppm at site 1 and 38 ppm at site 2). Nitrate was stable in the percolation stream below the root zone. Annual additions to subsurface waters were estimated at 76% of input N at site 1 and 65% at site 2. The range of PO₄-P in subsurface waters was 0.5 to 1.5 ppm at site 1 and 0.04 to 1.8 ppm at site 2; average waste water concentrations were 3 and 35 ppm. The highest concentrations in subsurface water were found in spring. Annual subsurface discharge was estimated at 27% of input P at site 1 and 2% at site 2. The extensive removals of PO₄ and the similar concentrations encountered in subsurface waters are of theoretical and practical interest since PO₄-P had already accumulated in soil profiles at both sites in quantities which exceed the Langmuir maxima for nonirrigated control soils. During seasons of major irrigation input, NO₃ appeared in subsurface waters in concentrations exceeding public health standards; PO₄ concentrations exceeded environmental guidelines at all times except where irrigation was discontinued during the winter at site 2. Soil systems appeared poised to discharge at the observed rates because of the large quantities of organic N and fixed P which had accumulated in the profiles over 20 years operation at site 1, and 10 years at site 2. The rate of residual accumulation in soil could have been reduced by harvest, to extend system life materially. The harvest potential of three grass clippings per season removed for silage, was estimated experimentally at 31% of input N at both sites and 80% of input PO₄ at site 1; 27% at site 2.

Quantitatively evaluating the effects of multiple factors on the performance levels of different irrigation methods under a limited water supply in the water-food-economy nexus at the regional scale is of great significance; such evaluations can facilitate the selection of appropriate irrigation methods and schemes to reduce the contradiction between the water shortage and grain production circumstances. In this study, the distributed SWAP-WOFOST (Soil-Water-Atmosphere-Plant-WOrld FOod STudy) model was applied to a typical area of severe deep groundwater overexploitation in the North China Plain. This model was used to simulate various scenarios of sprinkler irrigation (SI) and limited surface irrigation (LSI) under the three limited irrigation quotas (i.e., 75 mm, 150 mm and 225 mm) and to further quantify the differences in crop yield, evapotranspiration and water productivity (WP) between the two irrigation methods by considering three rainfall levels and 66 soil texture profile (STP) types. Then, the impacts of irrigation methods on farmers’ net income were analyzed; the increasing extents of SI implementation scale and workday wage to improve farmers’ net income were estimated according to irrigation, rainfall and soil conditions. Under a specific limited irrigation quota, the yield and WP of winter wheat under LSI were greater than those under SI without fertigation in more than 92% of the 66 STP types under the three rainfall levels, with yield differences mainly in the range of 200–1600 kg hm−2 and WP differences mainly in the range of 0–0.5 kg m−3. In no more than five STP types (e.g., sandy or loamy sandy soil in the five layers), the yield and WP under LSI were lower than those under SI. Relative to the evapotranspiration under LSI, the evapotranspiration under SI did not show the same trend, while the ratio of transpiration to evapotranspiration under SI decreased in more than 98% of the STP types. For different irrigation quotas and rainfall levels, the farmers’ net incomes under SI were 374–1517 yuan hm−2 greater than those under LSI for up to five STP types, and they were 0–3000 yuan hm−2 lower than those under LSI for the other 92% of the STP types. When labor could be saved by more than 8 d hm−2 by improving the implementation scale of SI and the workday wage could increase to more than 100 yuan d−1, SI was recommended to obtain higher farmers’ net income in more STP types in the study area.

Irrigation water coming from freshwater bodies that suffer toxic cyanobacterial blooms causes adverse effects on crop productivity and quality and raises concerns regarding food contamination and human exposure to toxins. The common agricultural practice of spray irrigation is an important exposure route to cyanotoxins, yet its impact on crops has received little attention. In the present study we attempted an integrated approach at the macro- and microscopic level to investigate whether spray or drip irrigation with microcystins (MCs)-rich water differently affect spinach performance. Growth and functional features, structural characteristics of stomata, and toxin bioaccumulation were determined. Additionally, the impact of irrigation method and water type on the abundance of leaf-attached microorganisms was assessed. Drip irrigation with MCs-rich water had detrimental effects on growth and photosynthetic characteristics of spinach, while spray irrigation ameliorated to various extents the observed impairments. The stomatal characteristics were differently affected by the irrigation method. Drip-irrigated spinach leaves showed significantly lower stomatal density in the abaxial epidermis and smaller stomatal size in the adaxial side compared to spray-irrigation treatment. Nevertheless, the latter deteriorated traits related to fresh produce quality and safety for human consumption; both the abundance of leaf-attached microorganisms and the MCs bioaccumulation in edible tissues well exceeded the corresponding values of drip-irrigated spinach with MC-rich water. The results highlight the significance of both the use of MCs-contaminated water in vegetable production and the irrigation method in shaping plant responses as well as health risk due to human and livestock exposure to MCs.