Agroforestry practices have tremendous potential within the Appalachian region because the steep terrain, acid soils, and high rainfall suggest that sustainable agroecosystems might be best achieved by developing perennial systems that include a tree component. An agroforestry system improves soil physical and chemical properties, maintains organic matter, improves nutrient cycling, reduces soil erosion, and maintains the structural integrity of the soil. Rural communities dependent on both agriculture and forestry may benefit from products and services an agroforestry system offers.
Landowners in the Appalachian region typically have some areas with steep slopes that are subject to erosion. Soils have shallow A horizons that are highly leached and thus acidic. Land use in this region is devoted to forests and pasturing of livestock for cowcalf production. Historically, there has been little integration of these two land use systems.
Agroforestry can diversify farm income, reduce offfarm adverse environmental impacts, and contribute to sustainable land use practices. However, to achieve this potential, quantitative data are needed to validate the benefits of integrating trees in a farming system. Furthermore, site specific data are needed to definitively demonstrate how an agroforestry system can increase productivity in present landscapes and the economic viability of a given land use.
The Whitethorne Agroforestry Project was established in 1995 to research and demonstrate the practical and economic feasibility of a multi-faceted agroforestry system within the humid, temperate, Appalachian region. This is a cooperative project between the USDA Agricultural Research Service’s Appalachian Soil and Water Conservation Research Laboratory at Beaver, WV, and the Forestry Department of Virginia Tech at Blacksburg, VA.
The project is a 10 ha study site located approximately 16km from Virginia Tech’s main campus on a 600 ha agricultural experiment station at Whitethorne, VA (Fig. 1).
It was established with the following research and demonstration objectives: (1) to demonstrate the feasibility of a multi-faceted agroforestry system, (2) to determine tree/grass/livestock interactions and how these components might be incorporated in a traditional agricultural or grazing system, (3) to determine the most effective tree establishment techniques in agroforestry systems, and (4) to identify and test the utility of additional potential agroforestry tree species.
The Appalachian region has great potential for integrated land use systems. In an effort to demonstrate this, a silvopasture study has been implemented to compare the land equivalency and productive capacity of a strictly hay pasture and two pastures in a silvopastoral arrangement. Each pasture will be monitored to determine overall forage biomass and productivity. Secondly, the most cost effective method of establishing agroforestry tree species in existing pastures will be tested.
The study consists of three replicate blocks in a complete randomized design (Fig. 1). The blocks are comprised of three 1 acre plots. Each plot is planted to a cool season grass (orchardgrass Dactylus glomerata) and legumes (red clover Trifolium repens and ladino clover T. pratense). The control plot is strictly forages. On the two remaining plots in the block, black walnut (Juglans nigra) and honey locust (Gleditsia triacanthos) have been superimposed on the hay pasture to create a silvopastoral system. The trees are planted on 2.5 m x 12.5 m spacing with the expectation that eventual leave trees will be on 12.5 m x 12.5 m spacing. The variables to be tested are biomass production, tree/forage/livestock interactions, forage yield, walnut production, honey locust pod yield, cultivar adaptability, and economic competitiveness of the 3 systems.
Light, water, and nutrients are three resources critical for plant growth. In a silvopastoral system, the objective is to manage the forage and tree crops in a spatial and temporal array so that the allocation of these resources optimizes the system’s total productivity. In this study, the goal is to determine the optimum tree density that maximizes total system production.
In this study, black walnut and honey locust trees have been planted in an existing orchardgrass, red clover and ladino clover pasture at different spacing to create a density gradient. A natural moisture gradient is present on the site with the landscape’s 20% slope that is perpendicular to the planting density gradient. Light, water, and nutrient availability to trees and forages will be assessed along the slope gradient as a function of tree density. Forage output will be measured to ascertain tree density impacts on spatial and temporal forage production. Mechanisms of compatibility and competition between trees and the forage crops will also be defined.
In the initial stages of tree growth and establishment, resource allocation between tree and forage will be mathematically modeled using the Silvopast model. The modeling information will then be compared against the actual field data to validate the model’s predictions of tree and forage interactions. Tree density will be evaluated within this study for effects on soil water dynamics, light and nutrient budgeting, forage yield, pod yield, walnut production, tree growth response, and overall economic return.
In J. Russell Smith’s 1929 book Tree Crops: A Permanent Culture, a variety of trees were proposed for agroforestry use in the temperate zone. Some significant research has been conducted on black walnut, honey locust, and black locust, but more evaluation of fruit and nut tree species is needed for their possible inclusion in temperate agroforestry systems. Research and investigation of prospective trees will facilitate
their use by practitioners and enable introduction of various tree species into a variety of land use settings. Current trial species include pawpaw (Asimina triloba), hazelnut (Corylus americana), American chestnut (Castanea dentata var. sweet hart), and black walnut (Juglans nigra). Prospective species to be planted are pecan (Carya illinoensis), persimmon (Diospyros virginiana), and royal paulownia (Paulownia tomentosa).
Agricultural productivity in the Appalachian region could benefit from the integration of agroforestry techniques into the topographically diverse landscape. Rural communities dependent on both agriculture and forestry may benefit from the proposed products and services an agroforestry system offers. The Whitethorne Agroforestry Project, although just established, is an endeavor to provide quantitative data and definitive demonstration of how agroforestry can be implemented within this region and the overall humid, temperate zone as a sustainable and productive land use option.