Silvopastoral Agroforestry: A Profitable Option for the Pacific Northwest’s Marginal Farmland

Garry Stephenson

Thousands of acres of marginal farmland in the higher rainfall portions of Oregon and Washington have limited cropping options. Poor soils, steepness, lack of available irrigation and other problems have limited use to either grazing or timber production. Historically, these areas have been over-cut and over-grazed – not managed for sustainability.

Since 1990, Rising Oak Ranch, located near Lebanon, Oregon, has collaborated with Oregon State University Extension agriculture and forestry faculty to create an applied research and demonstration area. Influenced by approaches from New Zealand, the project is examining agroforestry as a system that can provide a sustainable and profitable use for marginal farmland.

Agroforestry is the planned combination of trees with one or more crops. Although large incomes can be generated by growing trees alone, decades are required to realize profits. Therefore, many landowners are reluctant to plant woodlands. Agroforestry combines trees with a crop that produces a regular income for the landowner during the years when trees are growing to merchantable size. This system can be managed in perpetuity.

Silvopastoral agroforestry combines forage and livestock production with timber production. These agroforests may be established as new plantings or in older woodlands that are pruned and thinned to accept planted forages. Also referred to as silvopastures, this system produces meat, wool, milk or other animal products in addition to timber. Management intensive grazing compliments this system.

The project at Rising Oak Ranch is investigating questions related to the design and culture of an agroforest. To date, the applied research is examining: 1) The performance of three tree species in grid and cluster plantings, 2) Systems of browse control to protect young trees from grazing damage by livestock and wildlife, 3) Forage "behavior" in new agroforests, and forage varieties appropriate for established agroforests.

The project is evaluating three species of trees (Douglas fir, KMX hybrid pine, and ponderosa pine) in three spacings (13-foot grid—traditional forest planting, 9X18-foot rectangular grid, and 6-foot triangular cluster on a 22-foot grid). These were planted on a 12-acre plot in 1990.

As with other planted woodlands, selection of species to fit a site is crucial. In this instance, the ponderosa and KMX pines had the highest survival rates and are performing well. Because of the additional sunlight, all trees have more limbs and require pruning. The first long-term data on the interaction of trees and geometric spacings will be collected during 2000. Spacings are discussed further in forage observations.

Techniques for protecting young trees from browse damage were also examined. These techniques were intended to allow for maximum forage utilization while minimizing damage to trees. Several "low-tech" methods, including tubes and repellents, were tried. None of them allowed for normal forage utilization and protection of the trees. Electric fence seems to be the best option for deterring livestock from browsing.

Applied forage research has consisted of plots related to: 1) The early 1990’s planting on 12 acres that examined forage and tree interactions in three geometric planting configurations and, more recently, 2) A small forage variety screening in an established woodland.

The configuration of the tree planting interacts with other parts of the management system, producing positive and negative effects depending on one’s management goals. The system that has numerous options to tailor to a site or to the preferences of the owner/manager: 1) Grids can be more easily protected with electric fence to reduce browse damage and enhance forage utilization, 2) Clusters offer more area for forage production, 3) Grids are easier for farming activities during establishment but clusters provide a more "natural" grazing environment, 4) More casually spaced plantings can offer good forage production and are aesthetically pleasing.

Without good browse damage control, maintaining good forage utilization while trees are young is difficult. The resulting under-utilization of pasture leads to shifts in the forage community permitting less desirable grasses to thrive.

From the variety screening in the established woodland: 1) Dry matter yields appear to be approximately 2/3 that expected on open pasture sites, 2) Highest yielding and most persistent species are orchardgrass followed by tall fescue. Other species (perennial ryegrass, Kentucky bluegrass, subterranean clover) were not persistent. There are plans to examine smooth bromes in the future.

This project has been supported by a Western SARE on-farm research grant, economic development funds through the Oregon Regional Strategies Program, and a grant from Cascade West RC&D. Seed was donated by Ampac Seed Inc. of Tangent, Oregon and Modern Forage Systems of Ferndale, Washington.

Garry Stephenson
Extension Small Farm Program
Oregon State University
11849 NW 9th Street
Corvallis, OR 97331
Tel: (541) 757-6750
Garry.stephenson@orst.edu

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