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Per- and polyfluoroalkyl substances (PFAS) are highly persistent synthetic organic contaminants that can cause serious human health concerns such as obesity, liver damage, kidney cancer, hypertension, immunotoxicity and other human health issues. Integrated crop–livestock systems combine agricultural crop production with milk and/or meat production and processing. Key sources of PFAS in these systems include firefighting foams near military bases, wastewater sludge and industrial discharge. Per- and polyfluoroalkyl substances regularly move from soils to nearby surface water and/or groundwater because of their high mobility and persistence. Irrigating crops or managing livestock for milk and meat production using adjacent waters can be detrimental to human health. The presence of PFAS in both groundwater and milk have been reported in dairy production states (e.g., Wisconsin and New Mexico) across the United States. Although there is a limit of 70 parts per trillion of PFAS in drinking water by the U.S. EPA, there are not yet regional screening guidelines for conducting risk assessments of livestock watering as well as the soil and plant matrix. This systematic review includes (i) the sources, impacts and challenges of PFAS in integrated crop–livestock systems, (ii) safety measures and protocols for sampling soil, water and plants for determining PFAS concentration in exposed integrated crop–livestock systems and (iii) the assessment, measurement and evaluation of human health risks related to PFAS exposure.

The Animas River provides irrigation water in northwestern New Mexico and the Navajo Nation. Concerns regarding the river water quality arose on August 5, 2015, when approximately 11.35 million liters of heavy metal contaminated water was accidentally released from the Gold King Mine into the Animas River. This study sought to determine the total concentrations of 7 heavy metal(loid)s (As, Pb, and Zn as metals of concern and Fe, Mn, Ca, and Cu as metals of interest) using portable X-ray fluorescence (PXRF) in two agricultural fields and compare these values to Environmental Protection Agency (EPA) regional screening levels (RSL). Total concentrations of 6 out of 7 metals were below the RSL; only As exceeded the soil screening value of 7.07 mg kg−1 at some locations in the agricultural fields. We also determined water-soluble (WS) and exchangeable fractions (Ex) of As that might be available for agricultural crop uptake using sequential extractions. The WS-As ranged from 0.014 to 0.074 mg kg−1 and Ex-As ranged from 0.135 to 0.248 mg kg−1 and thus were less than 1 and 3% of the total As concentration respectively (ranging from 5.62 to 14.79 mg kg−1) and not considered a threat for plant tissue accumulation. While the concentrations of As observed in the agricultural fields may have exceeded screening levels, the As was not apparently plant available and its risk to crops was determined to be low.

Extractant for estimating plant available arsenic (As) in soil has not been universally established. Moreover, to assess and monitor the complex chemical behaviour of arsenic (As) in soil and subsequently its transfer in crops, a suitable extraction protocol considering the soil properties in relation to crop uptake is required. For this purpose, a pot experiment was conducted to evaluate the suitability of the extractants for determination of extractable As in soil and risk assessment by solubility-free ion activity model (FIAM) with rice (variety: Sushk Samrat) as the test crop. Soil in bulk was collected from six locations of Indo-Gangetic Plain of Bihar, India, varying in physicochemical properties to conduct the pot experiment using five doses of As (0, 10, 20, 40 and 80 mg kg−1). Six extractants namely 0.2 (M) NH4-oxalate, 0.05 (N) HCl + 0.025 (N) H2SO4, 0.5 (M) KH2PO4, 0.5 (N) NH4F, 0.5 (M) NaHCO3 and 0.5 (M) EDTA were used. The results revealed that 0.5 (M) KH2PO4 gave the best correlation with the soil properties and crop uptake and can be considered a suitable extractant of As. Regardless of the As dose and the soil type used, in rice tissue, concentration of As followed the order root > straw > leaf and grain. As high as 94% variation in As content in rice grain could be explained, when 0.5 (M) KH2PO4 extractable As is being used as input for solubility-FIAM. Extractable As cannot be determined by atomic absorption spectrophotometer (AAS) coupled with vapour generation accessory (VGA) when 0.5 (M) EDTA was used as an extractant.

Evaluation of soil-phosphorus (P) tests is critical to ensure the accuracy of fertilizer recommendations to optimize crop yield while minimizing negative environmental consequences. Olsen-P is the most commonly used soil-P test for alkaline calcareous soils found in Idaho and the Western United States. The Bray-1 test is commonly used in the Pacific Northwest (PNW) on neutral to acidic soils but underestimates P in alkaline calcareous soils. Mehlich-3 has been evaluated throughout various regions in the United States. Little data evaluating the test exists on soils in the Western United States. Additionally, the comparatively newly developed H3A test, a component of the soil health tool, has not been widely evaluated on alkaline calcareous soils. Soil samples from the 0- to 30-cm depth were collected from agricultural fields throughout Idaho and analyzed using Bray-1, H3A, Mehlich-3, and Olsen P extractants. Results suggested that Olsen P was strongly correlated with Mehlich-3, while Bray-1 and H3A were not correlated with Olsen P. Both the Bray-1 and H3A test underestimated extractable P when compared with the Olsen P test, whereas the Mehlich-3 overestimated. A threshold point in calcium carbonate (i.e., inorganic carbon (IC)) of 6.7 and 5.1 mg kg-1 for the Bray-1 and H3A was obtained, respectively, that indicated inorganic carbon concentrations at or above these levels result in underestimation of extractable soil P. Thus, Mehlich-3 was very strongly correlated to Olsen P and could be evaluated for use in alkaline calcareous soils whereas Bray-1 and H3A have notable issues that would limit their applicability.

Information on the effects of phosphorus (P) and sulfur (S) applications on crop response and soil-P status of two-row malt barley (Hordeum vulgare L.) under high-input conditions are limited in al...

In this study, an inexpensive Nix Pro (Nix Sensor Ltd.) color sensor was used to develop prediction models for soil iron (Fe) content. Thirty‐eight soil samples were collected from five agricultural fields across the Animas watershed to develop and validate soil Fe prediction models. We used color space models to develop three different parameter sets for Fe prediction with Nix Pro. The different color space sets were used to develop three new predictive models for Nix Pro‐based Fe content against the lab‐based inductively coupled plasma analyzed Fe content. The model performances were assessed using the coefficient of determination, root mean square error, and model p‐value. Three models (International Commission on Illumination's lightness, ±a axis (redness to greenness), and ± b axis (yellowness to blueness) [CIEL*a*b]; red, green, blue [RGB]; and cyan, magenta, yellow, key [black] [CMYK]) were significant in predicting the Fe content using colorimetric variables with R2 ranging from 0.79 to 0.81. The mean square prediction error (MSPE) and Kling–Gupta efficiency (KGE) Index were calculated to validate models and CMYK was predicted to be a better model (MSPE = 0.13; KGE = 0.601) than CIEL*a*b and RGB models. The results suggest Nix Pro is useful in predicting soil Fe content.

Optimizing barley (hordeum vulgare L.) production in Idaho and other parts of the Pacific Northwest (PNW) should focus on farm resource management. The effect of post-harvest residue management on barley residue decomposition has not been adequately studied. Thus, the objective of this study was to determine the effect of residue placement (surface vs. incorporated), residue size (chopped vs. ground-sieved) and soil type (sand and sandy loam) on barley residue decomposition. A 50-day(d) laboratory incubation experiment was conducted at a temperature of 25°C at the Aberdeen Research and Extension Center, Aberdeen, Idaho, USA. Following the study, a Markov-Chain Monte Carlo (MCMC) modeling approach was applied to investigate the first-order decay kinetics of barley residue. An accelerated initial flush of residue carbon(C)-mineralization was measured for the sieved (Day 1) compared to chopped (Day 3 to 5) residues for both surface incorporated applications. The highest evolution of carbon dioxide (CO2)-C of 8.3 g kg-1 dry residue was observed on Day 1 from the incorporated-sieved application for both soils. The highest and lowest amount of cumulative CO2-C released and percentage residue decomposed over 50-d was observed for surface-chopped (107 g kg-1 dry residue and 27%, respectively) and incorporated-sieved (69 g kg-1 dry residue and 18%, respectively) residues, respectively. There were no significant differences in C-mineralization from barley residue based on soil type or its interactions with residue placement and size (p >0.05). The largest decay constant k of 0.0083 d-1 was calculated for surface-chopped residue where the predicted half-life was 80 d, which did not differ from surface sieved or incorporated chopped. In contrast, incorporated-sieved treatments only resulted in a k of 0.0054 d-1 and would need an additional 48 d to decompose 50% of the residue. Future residue decomposition studies under field conditions are warranted to verify the residue C-mineralization and its impact on residue management.

Soil phosphorus testing made great strides with multiple chemical tests proposed and implemented that have been used for fertilizer management programs for crop production during the previous century. In the latter part of the previous century, the environmental impact of excess nonpoint phosphorus loading from the landscape (e.g. agricultural lands) to waterbodies became an issue of increased concern and soil phosphorus testing came to the forefront of management and monitoring. This article will provide a general overview of the usage of phosphorus testing for agronomic purposes in the United States.

Properties of biochar are thought to determine whether phosphorus (P) sorption or increased P availability occur following biochar application to sandy acidic soil; the effect of soil properties on P retention in biochar-amended acid soils remains largely unexplored. Our objective was to determine effects of hardwood biochar and poultry litter biochar on P sorption and release from two soils differing in P retention properties at three rates of biochar addition. Soils as well as soil + biochar mixtures were treated with 12 levels of solution P concentrations. Phosphorus concentration and the amount of P sorbed for each level of P addition at the end of the incubation showed that after P addition corresponding to the soil P storage capacity (SPSC) as determined prior to biochar application, P retention abruptly declined for all treatments irrespective of biochar type. Biochar did not diminish the capacity of the two soils to tenaciously bind P added as a soluble inorganic source. Also, the maximum P retention capacity of the soil (Smax) increased as amount of biochar applied increased. Biochar-enhanced P sorption at high solution concentrations would be environmentally beneficial only if the sorption were strongly hysteretic such that subsequent P release is minimal as concentrations approach background levels. X-ray diffraction analysis of the biochar after incubating at high P solution concentration did not reveal formation of a stable crystalline P phase. This study provides evidence that the amount of P that can be “safely” added to soils amended with biochar depends significantly upon the P retention property of the soil, and not only the biochar characteristics.

Equilibrium models used for predicting phosphorus (P) loss from a site often use the Langmuir strength of P bonding, KL and the P sorption maximum, Smax, or the Freundlich adsorption coefficient, KF, obtained from traditional isotherms, as model input parameters. The overall objective of the study was to develop a protocol to allow estimation of isotherm parameters for soils using simple extraction techniques without generating time-consuming isotherms. A threshold P saturation ratio (PSR; molar ratio of P to [Fe+Al] in an oxalate- or soil test extracting solution) is the PSR value at which P release from a soil increases abruptly. The soil P storage capacity (SPSC) indicates the amount of P a soil can hold before becoming an environmental risk: SPSC = (Threshold PSR-Soil PSR)*(Fe+Al)*31 mg kg−1. Soil samples with varying P-impact levels from four manure-impacted sites were collected by horizon (Ap, E, and Bt). The PSR, SPSC and isotherm parameters (KL, KF, Smax) were determined for all soils and regression equations among various parameters evaluated. Equations were validated with soils data from three other sites. Relationship between predicted and determined parameters were significant (R2 = 0.98 for KL and 0.95 for KF and Smax) suggesting that isotherm parameters can be obtained from P, Fe, and Al in an oxalate or soil test solution without generating time- and resource-consuming isotherms.