Factors Affecting Sugar Accumulation and Fluxes in Warm- and Cool-Season Forages Grown in a Silvopastoral System

et al. 2021

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The Soil Management Assessment Framework (SMAF) is a quantitative soil quality (SQ) evaluation tool that is widely applied to assess soil response to specific agricultural management practices over time. Considering the reported SQ benefits of agroforestry (AF) systems and the potential usefulness of SMAF, the objective of this study was to evaluate the effects of tree species (pecan [Carya illinoinensis (Wangenh.) K. Koch] and northern red oak [Quercus rubra L.]), soil fertility source (poultry litter [PL] and inorganic N fertilizer [control]), and soil depth (0-15 and 15-30 cm) on SMAF-derived SQ indices after 17 yr of management at an AF site in northwest Arkansas. Averaged across soil depth, soil organic C scores under red oak with PL application had a lower score (0.48) than red oak fertilized with inorganic N (0.60) and pecan receiving long-term PL applications (0.60), which did not differ from pecan with inorganic N fertilizer application (0.51). Averaged across soil depth, the soil quality index (SQI) for pecan receiving PL applications was 1.1 times greater than that under red oak receiving PL and soils under pecan receiving inorganic N fertilizer. Soil quality assessments use in AF are novel, as SMAF has not been used to identify soil health in these systems, although specific tree crop codes need to be developed in SMAF. Results of this study demonstrate that soils planted under various tree species respond dissimilarly to fertilizer sources and that management may improve overall SQ.

Section: Introductionmentioning

confidence: 99%

Soil quality assessment of an agroforestry system following long‐term management in the Ozark Highlands

Ylagan

Amorim

et al. 2021

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“…Specifically, CO 2 flux was greater ( P ≤ .05) in the fertilized native mix (10.54 μmol m −2 s −1 ) than in the unfertilized native mix, and the fertilized and unfertilized orchardgrass (8.46, 8.02, and 8.77 μmol m −2 s −1 , respectively), which did not differ ( P ≥ .05) among the other three treatment combinations. By mid‐July, orchardgrass had reduced growth due to air temperatures at or above 25 °C (Niyigena et al., 2021), which corresponded to reduced CO 2 flux from lower root respiration contributions (Figure 1; Bush et al., 2006). With little active production of the aboveground portion of the plant, root exudate release is slowed, thus reducing nutrients for microbial growth and activity in the rhizosphere.…”

Section: Resultsmentioning

confidence: 99%

“…× Pinus taeda L.). Forage establishment details can be found inNiyigena et al (2021). Briefly, two forage groups, a cool-season non-native orchardgrass (C 3 ; photosynthetic pathway) and a native warm-season (C 4 ; photosynthetic pathway) grass mixture (8:1:1 big bluestem [Andropogon gerardii Vitman], little bluestem [Schizachyrium scoparium (Michx.…”

mentioning

confidence: 99%

Soil CO₂ evolution is driven by forage species, soil moisture, grazing pressure, poultry litter fertilization, and seasonality in silvopastures

Adams

Sauer

2021

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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.

“…After establishment, alleys were treated with Plateau (ammonium salt of imazapic) F I G U R E 1 Daily mean volumetric soil water content and daily mean soil temperature for the wet (aquic) and dry (udic) treatments from May to July in (a) 2017 at 15 cm, (b) 2017 at 60-75 cm, (c) 2018 at 15 cm, and (d) 2018 at 60-75 cm at a rate of 0.28 kg ha −1 (23.6% a.i. ; Niyigena et al, 2021). The site receives an average (30-yr mean) annual precipitation of 1,232 mm and has an average ambient temperature of 14.5˚C (NCDC, 2019a(NCDC, , 2019b.…”

Section: Core Ideasmentioning

confidence: 99%

“…After establishment, alleys were treated with Plateau (ammonium salt of imazapic) at a rate of 0.28 kg ha −1 (23.6% a.i. ; Niyigena et al, 2021). The site receives an average (30-yr mean) annual precipitation of 1,232 mm and has an average ambient temperature of 14.5 ˚C (NCDC, 2019a(NCDC, , 2019b.…”

Section: Core Ideasmentioning

confidence: 99%

Root decomposition in silvopastures is influenced by grazing, fertility, and grass species

Adams

Kharel

et al. 2021

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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.