No abstract

Soil health is an emerging paradigm for which much research in row crop agriculture has been undertaken. Research involving grazing lands and soil health has not been as active, a feature partially attributed to (i) greater erosional rates in cropland, (ii) loss of soil organic matter and reduced soil structure attributed to annual tillage practices, (iii) cash flow from cropland is easier to visualize than the value-added nature of grazing lands, and (iv) there exists more competitive grant funding sources for croplands. Grazing lands do require soil quality augmentation and investment in soil health to optimize their ecosystem services potential. This manuscript, with an emphasis on beef cattle grazing in the central USA, attempts to survey the literature to (i) identify the influence of grazing on important ecosystem services provided by Mollisols and Alfisols, (ii) develop a listing of soil indicators that may be selected to quantify and credential soil quality, and (iii) develop guidelines that align soil indicators and changes in grazing management to support the restoration of ecosystem services.

Nitrogen transport from agriculture production fields raises the specter of environmental degradation of freshwater resources. Our objectives were to document and evaluate nitrate-N, ammonium-N, phosphorus and other nutrients emanating from a 40-ha controlled subsurface irrigation drainage technology coupled in series with a denitrification bioreactor. The intent of the denitrification bioreactor is to create an environment for anoxic microbial populations to support denitrification. We monitored the tile-drainage effluent and denitrification bioreactor water chemistry under a corn-soybean rotation to estimate the nutrient concentrations and the competence of the denitrification bioreactor to foster denitrification. Nitrate-N bearing tile drainage effluents ranged from less than 1.5 to 109 mg NO 3-N/L, with the nitrate concentration differences attributed primarily to the: 1) timing of nitrogen fertilization for corn, 2) soil mineralization and residue decomposition, and 3) intense rainfall events. The denitrification bioreactor was highly effective in reducing drainage water nitrate-N concentrations providing the rate of water flow through the denitrification bioreactor permitted sufficient time for equilibrium to be attained for the nitrate reduction reactions. The nitrate-N concentrations entering the denitrification bioreactor ranged from 0.4 to 103 mg NO 3-N/L in 2018, whereas the outlet nitrate concentrations typically ranged from 0.3 to 5.2 mg NO 3-N/L in 2018. Nitrate tile-drainage effluent concentrations in 2019 were marginal, given soybeans obtain nitrogen from biological nitrogen fixation. Nutrient uptake by corn reduced the soil nitrate leaching pool and created nitrogen-bearing biomass, features important for formulating best management practices.

Constructed wetlands are engineered structures designed to simulate processes of natural wetlands to mitigate anthropogenic organic and inorganic materials to shelter soil and water resources. This review focuses on the global interest in constructed wetland application to sustain soil health and water quality and water abundance. Engineering criterion remains a function of nutrient chemistry and load with suitability factors including the local soil and hydrogeology constraints, climate, vegetation selection, the degree of required influent improvement, and reactor types and sizes. Future research needs to focus on: 1) reactor designs criteria, 2) the biology of the microbial community, 3) selection criteria for native vegetation, and 4) criteria to reapply treated water to foster land productivity, especially for region's experiencing water deficiencies.

Selenium is a trace element in animal nutrition provided through forage. Vegetation should accumulate adequate levels to meet this livestock requirement. This study assessed southeastern Missouri soils for their selenium concentrations. Multiple sites across southeastern Missouri were sampled, from which a total of twenty-six soils were collected. Parent materials ranged from coarse to fine-textured alluvium and terrace deposits, colluvium, loess, limestone residuum and rhyolite residuum from poor to well-drained soils. The mean whole soil selenium contents ranged from less than 0.1 mg Se kg −1 for the Kaintuck pedons to 1.0, 2.2, and 2.4 mg Se kg −1 for the Irondale, Killarney, and Frenchmill pedons. For individual soils, Menfro pedons were deep, well-drained soils developed in loess. Paired Menfro pedons having similar soil morphology and having A-E-BE-Bt-C horizon sequences were selected and the greatest selenium concentrations were in the argillic horizons. Soils having fine textures (clayey) had moderate selenium concentrations, whereas soils having coarse textures (sandy) revealed minimal selenium concentrations. A wide soil selenium concentration variation was shown; however, no toxic selenium levels were measured. Therefore, soil selenium toxicity is not a regional issue. Noting that soil selenium concentrations in medium to fine-textured soils are appropriate for providing selenium to livestock, the need to artificially soil incorporate selenium or add selenium into the livestock ration remains critical for coarse-textured soils.