Carbon and N Dynamics in a Silvopasture System for Sustainable Timber, Forage and Goat Production in the Southeastern U.S.A.

A silvopasture agroforestry system presents the opportunity to increase land productivity and improve cash flow by combining income from agriculture, forestry, and animal production on the same piece of land. In addition, silvopasture offers numerous environmental benefits such as nutrient recycling, erosion control, increasing the diversity of plants and animals, and carbon sequestration. The long-term goal of this project is to develop and evaluate silvopastoral systems for the simultaneous production of pine sawlogs, forage, and meat goats in order to increase productivity, profitability, and sustainability on small and medium sized farms in the Black Belt region of the Southeastern United States. The study is being done at the Federation of Southern Cooperatives, Epes, Alabama. A seven year old loblolly pine plantation was thinned from 600 to 150 trees per acre starting in 2006. Paddocks were fenced out and treatments consisting of 0, 4, and 8 goats per acre stocking rate treatments and an enhanced soil management treatment were studied in 2007, 2008 and 2009. Baseline soil analyses in 2007 showed that the soil at project site was  characterized by low pH (<5) and low soil C, averaging 12 to 16 g kg^-1 in top 15 cm of soil and less than 10 g kg^-1 in the 15-60cm depth, in addition to being critically deficient in major soil nutrients such as nitrogen. Soil analysis results after three years of study show that animal grazing and soil management for improved forage production can significantly increase available soil nutrients through nutrient cycling in the form of animal manure. We hypothesize that grazing without inorganic fertilizer application can, in the long-term, increase soil C and also provide adequate soil N to support forage and tree growth, thereby making the silvopasture system both economical and environmentally sustainable.