Southern-Pine Silvopasture Systems: Forage Characteristics, Soil Quality, and Landscape Utilization by Cattle

Abstract

Silvopasture is considered a more attractive land management option for diversified economic returns and environmental quality compared to open-pasture (pasture without trees) monocultures. However, little is known about temporal and spatial dynamics of pasture-plant species composition, forage productivity, and forage and soil quality as pasture-to-silvopasture conversion proceeds or the possible benefits silvopasture systems offer for improved forage and landscape utilization by grazing animals. Major objectives of this research were to determine the influence of: 1) pasture type (silvopasture versus open-pasture) on forage and soil parameters, and the distribution and behavior of cattle; 2) N source (legume-N versus fertilizer-N) on forage and soil parameters; 3) forage species and soil pH level on soil quality parameters. To quantify pasture-type and N-source effects, studies were conducted in a young (3-7 yr) longleaf pine (Pinus palustris)-bahiagrass (Paspalum notatum) silvopasture and open bahiagrass pasture at Americus, Georgia. Pasture-plant species composition, biomass, and quality (2003-2007) and soil quality parameters (2005-2007, water stable aggregates, WSA; density of fungal hyphae, DFH; penetration resistance, PR) were evaluated. Legume-N (Trifolium incarnatum) and fertilizer-N treatments were applied to both pastures from 2005 to 2007. A second field study was conducted in a 20-yr old loblolly-pine (Pinus taeda) silvopasture and open-pasture at Chipley, Florida in 2007 to examine diurnal distribution and behavior of cattle (Bos taurus) and relationship to microclimate and forage characteristics. Short-term (12-wk) impacts of forage species and pH level (field-state versus adjusted-pH) on soil quality (WSA and DFH) were studied in coastal plain soil microcosms under protected culture during three experimental periods: fall 2005 and summer and fall 2006. Compared to open-pasture, young longleaf-pine silvopasture produced similar forage shoot dry matter with lower quality; lower levels of WSA and PR were detected in silvopasture. Legumes improved forage productivity and forage and soil quality compared to fertilizer-N use. Cattle distribution was more even and grazing hours were longer in mature loblolly-pine silvopasture versus open-pasture. WSA levels in microcosm soil under subterranean clover (Trifolium subterraneum) were greater than or equal to WSA levels in soils under other cool-season forages; the same relationship was observed for WSA levels in soil under Illinois bundleflower (Desmanthus illinoensis) versus other warm-season legumes. WSA and DFH levels were higher in field-state versus adjusted-pH soil.