Grass root production and decomposition is a major source of C entering soils, although rates are largely unknown based on edaphic and management factors. Therefore, study objectives were to evaluate four explanatory variables including forage species (native and nonnative), fertility (poultry litter and a control), soil moisture (udic and aquic), and pasture management (grazed and an ungrazed control) in order to evaluate driving factors for root turnover and subsequent soil organic matter formation in silvopastoral systems using the root litter bag technique. Native grass root decomposition was accelerated relative to the nonnative forage based on root mass balance, as well as the exponential decay function, likely owing to greater fiveand six-C sugars and more digestible root tissues of native grasses. These physiochemical results suggest more favorable microbial food sources, which culminate in faster decomposition and greater microbially derived organic matter. Overall, there was greater root sloughing and subsequent soil organic matter formation potential with native grass species and poultry litter applications, with soil moisture affecting decomposition to a lesser extent. This study contributes to the understanding of complex interactions of grass species, soil moisture, nutrients, and grazing, which controls primary productivity, as well as nutrient cycling and C sequestration in silvopastures.

Systems-level studies aimed at determining how soil properties are linked to plant production and ultimately animal response spatially are lacking. This study aims to identify if grazing pressure is linked to soil properties, terrain attributes, and above-ground plant accumulation and nutritive value in a silvopastoral (or integrated tree-livestock) system. Overall, cattle prefer grazing native grasses (2.81 vs. 1.24 h ha−1 AU−1) and udic (dry) landscape positions compared to aquic (wet) areas (2.07 vs. 1.60 h ha−1 AU−1). Greater grazing frequency occurs in udic soils with greater phosphorus and potassium contents and with accumulated forage with less lignin (P ≤ 0.05), which correspond to reduced elevation and greater tree height and diameter (shade) during summer mob grazing. Combining spatial monitoring technologies (both soil and animal) with forage allowance can optimize grazing systems management and sustainability spatially and temporally.

Abstract:Since soybean (Glycine max L. (Merr.)) yields greater than 6719 kg ha −1 have only recently and infrequently been achieved, little is known about the soil microbiological environment related to high-yield soybean production. Soil microbiological properties are often overlooked when assessing agronomic practices for optimal production. Therefore, a greater understanding is needed regarding how soil biological properties may differ between high-and average-yielding areas within fields. The objectives of this study were to (i) evaluate the effects of region on soil microbial carbon substrate utilization differences between high-(HY) and average-yield (AY) areas and (ii) assess the effect of yield area on selected microbiological property differences. Replicate soil samples were collected from the 0-10 cm depth from yield-contest-entered fields in close proximity that had both a HY and an AY area. Samples were collected immediately prior to or just after soybean harvest in 2014 and 2015 from each of seven geographic regions within Arkansas. Averaged across yield area, community-level carbon substrate utilization and Shannon's and Simpson's functional diversity and evenness were greater (p < 0.05) in Region 7 than all other regions. Averaged across regions, Shannon's functional diversity and evenness were greater (p < 0.05) in HY than in AY areas. Principal component analysis demonstrated that a greater variety of carbon substrates were used in HY than AY areas. These results may help producers understand the soil microbiological environment in their own fields that contribute to or hinder achieving high-yielding soybeans; however, additional parameters may need to be assessed for a more comprehensive understanding of the soil environment that is associated with high-yielding soybean.

Carbon cycling is a highly complex yet critical process, especially in silvopastures, which have multiple pools with the ability to store large amounts of C. However, it is largely unknown how site-specific variables, including edaphic factors, vegetation type, topography, and management, affect soil CO 2 flux in silvopastures. Therefore, this study aimed to evaluate CO 2 fluxes in a silvopastoral system as affected by soil moisture (udic and aquic), forage species (C 4 ; native grass mix and orchardgrass [C 3 ; Dactylis glomerata L.]), fertilization (poultry litter and a control), and grazing pressure (grazed and ungrazed). Temperature and volumetric water content (VWC) were measured simultaneous with flux measurements during summer grazing in 2018 and 2019. Averaged across years, fluxes were at least 20% greater (P ≤ .05) in the native mix fertilized with poultry litter than in the unfertilized native mix and fertilized or unfertilized orchardgrass, likely owing to increased microbial diversity activity in the rhizosphere of poultry litter-amended native grass species. Across years, CO 2 flux was 7% greater (P ≤ .05) in the fertilized ungrazed areas and 7% lower (P ≤ .05) in the unfertilized ungrazed areas, respectively, compared with both fertilized grazed and unfertilized grazed areas. Carbon dioxide flux was correlated (P ≤ .05) with sampling date, soil temperature, and VWC. Study results improve the understanding of C dynamics in complex silvopasture systems and may assist producers in their selection of forage species and nutrient sources when designing silvopastoral systems for enhanced regional sustainability.

Core Ideas Crop yield contests provide a unique research opportunity. Planting date is highly related to yield across yield contest sites. An early soybean production system is advantageous for high yields. Increasing soybean [Glycine max (L.) Merr.] yields requires a multi‐pronged approach. Annual state soybean yield contest fields can provide information about yield potentials and plant response differences between high and average‐yield producing areas. The objectives of this study were to i) assess plant physiological property and elemental seed concentration differences between high‐ (HY) and average‐yield (AY) areas and across soybean growth stages and ii) evaluate relationships among plant properties and yield across the seven regions of the “Grow for the Green” soybean yield contest in Arkansas. Seed yields in AY and HY areas averaged 74.4 and 88.3 bu/ac, respectively, in 2015. Harvest index, average seed weight, and seed K concentration differed (p < 0.05) by at least 10% across growth stages and between yield areas. Averaged across growth stage, aboveground dry matter and seed B and C concentrations differed (p < 0.05) by at least 0.7% between yield areas across regions. Averaged across yield area, seed N, P, Ca, Fe, Mn, Zn, Cu, and B concentrations differed (p < 0.05) by at least 2.5% across growth stages. Planting date was most strongly correlated with yield (p < 0.001; r = –0.62), confirming previous research. Encompassing a wide variety of landscapes and management systems, results of this study validate the importance of planting date to soybean yield. Additional factors need to be evaluated to discover stronger relationships with yield to continue closing the soybean yield gap.