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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.

Wheat (Triticum aestivum, L.) producers have the choice to retain or remove residue from the cropping system following grain harvest. In the U.S. Pacific Northwest and other regions, wheat residue is often sold to increase operational profitability, especially from higher-yielding systems. But there are several benefits to retaining residue, including recycling of mineral nutrients contained therein, though this is understudied. Therefore, the primary objectives of this research were to collect and analyze a large and diverse dataset on wheat residue nutrient uptake (N, P, K, Ca, Mg, S, Fe, Zn, Mn, Cu), develop tools to estimate nutrient amounts in residue, and make economic estimates of the fertilizer replacement value of those nutrients. This was accomplished by conducting replicated variety trials on five classes of wheat across many Pacific Northwest sites over two years, then collecting and analyzing data on wheat residue biomass, residue nutrient concentrations, and grain yield. The results showed that wheat residue contained a significant amount of nutrients, but was particularly concentrated in K. Production environment had the most substantial effect on residue mineral uptake amounts, due to site differences in yield and soil nutrient availability. To enable simple estimation of residue nutrient uptake across a broad range of wheat production levels, two estimation tools are presented herein. Economic analysis showed the substantial monetary value of residual nutrients. For example, in a high-yielding wheat crop (9 Mg ha−1), the average fertilizer replacement value of just residue N, P, K, and S was similar to the entire fertilizer budget to grow the crop (~$211 vs. $205 ha−1), not considering micronutrients in the residue or any nutrients removed through grain harvest. In making residue management decisions, wheat producers should consider the tradeoff between the immediate economic gains of residue sale and the multifaceted benefits of residue retention, including savings on future nutrient costs. [ABSTRACT FROM AUTHOR]

Biochar is a carbon-rich product obtained by biomass pyrolysis and is considered as a means of carbon sequestration. However, there is limited knowledge regarding responses of soil respiration and C-cycle enzyme activities to BC in a calcareous soil. In this study, different biochar AS, TS, PP, CS were applied to the soil at different rates (0.5, 1.0, and 1.5%) The highest increase in soil organic C content was observed in the TS treatment, while the AS treatment caused a slight increase of soil organic C. The highest MBC content was recorded in AS treatment and the lowest was observed in TS. The highest CO2-C emission was recorded in the TS treatment. In contrast, the lowest CO2-C emission was observed in the PP treatment due to its high recalcitrant C content and was attributed to a positive priming effect, stabilizing BC mineralization to improve the soil. The highest β-galactosidase enzyme activity was observed in the CS treatment and the lowest activity was observed in AS. The highest change in β-glycosidase enzyme activity was observed of PP treatment and the lowest was in AS biochar application. Thus, TS treatment is recommended to increase the organic C content of soils, and the PP biochar can be used to reduce CO2-C emission. The TS, PP, and CS can be applied to increase enzyme activities. The study clearly shows that the addition of BC to arid soils may have a high potential to improve soil enzyme activities and subsequent carbon sequestration and biochemical cycles. [ABSTRACT FROM AUTHOR]