Agroforestry is an intentional integration of trees and shrubs into agricultural systems to enhance environmental, economic and social benefits. Agroforestry aims to optimize productivity and conservation benefits within a set of integrated land use practices. This practice supports environmental stewardship and sustainable agricultural systems while providing additional income and ecosystem services.
Agroforestry integrates trees, shrubs, forages, grasses, livestock and crops in innovative, flexible combinations tailored to the needs of landowners.
In Oregon’s temperate climate, agroforestry consists of five main practices:
- Silvopasture
- Alley cropping
- Riparian forest buffers
- Windbreaks
- Forest farming
When properly designed, these practices can reduce pesticide use, prevent environmental degradation, improve agricultural productivity, increase carbon sequestration, improve pollinator habitat, support healthy soil and healthy ecosystems, provide diversified and stable incomes, and enhance wildlife habitat and biodiversity.
While designing and implementing any of these five practices, consider the compatibility of the species with the site, the compatibility among species, the farm equipment available and potential markets. Local natural resource professionals in Extension, the Natural Resources Conservation Service, local soil and water districts, the Oregon Department of Fish and Wildlife and your Oregon Department of Forestry office can provide information on restrictions or requirements for streamside protection or maintaining wildlife habitat and biodiversity.
Silvopasture
Silvopasture is the intensive management and growing of perennial grasses or grass- legume mixes in a forest stand for livestock pasture. In the United States, silvopasture management occurs across geographic regions and climate zones. Systems are established by planting trees into pasture; thinning trees in native forest or plantations and establishing forages; or integrating livestock into orchards or natural savannas. Silvopasture systems are managed for both forest products and forage, and may be one of the most applicable agroforestry practices for most of Oregon (Figure 1). Well-managed silvopastures employ agronomic principles, typically including introduced or native pasture grasses, fertilization and nitrogen-fixing legumes, and rotational grazing systems that employ short grazing periods that maximize vegetative plant growth and harvest.
Just letting cows graze in a natural woodland area without any type of tree or forage management is not considered a silvopastoral practice. Rotationally grazing livestock, planting, pruning and protecting trees, and monitoring forage quality are all part of silvopasture management. Proper design and planning, as well as a working knowledge of the silvopastoral components, can reduce the time and labor involved in establishing and managing the system.
A silvopasture practice will help you realize several benefits:
- Trees protect livestock from temperature extremes by blocking wind and snow in winter and providing shade in summer.
- Livestock benefit from improved forage quality.
- A reduced need for chemical or mechanical vegetation control.
- Trees can grow faster.
Douglas-fir and ponderosa pine are two dominant Pacific Northwest timber species that have been planted in recent silvopastoral systems in the region. However, other locally adapted conifers or hardwoods may be used either alone or in mixed-species stands. For example, red alder has been grown as a quick-rotation saw log between longer-rotation Douglas-fir clusters in silvopastures.
Well-managed silvopasture trees in Oregon have been known to produce as much as 16% greater diameter growth than similar trees in a typical forest plantation setting.
Recent research findings in Lincoln County, Oregon, show that cattle can be integrated into thinned Douglas-fir forest plantations, especially on south-facing slopes. The researchers recommend stocking rates of 4 and 6.5 acres per cow/calf unit under 25- and 55-year-old Douglas-fir thinned-forest silvopastoral systems, respectively.
Forages recommended for silvopastoral systems in Oregon include perennial ryegrass, orchard grass and tall fescue (with a mix of subterranean clover and white clover). These forages can perform well under 50% shade, depending on soil conditions and aspect. The clovers serve as biological sources that fix nitrogen for grass and trees and provide necessary crude protein for the grazing livestock. Match tree and forage selections to produce more palatable forage and more efficient grazing.
Trees for silvopasture systems are often planted at lower initial densities, such as 200–300 trees per acre, with more care devoted to individual tree growth. For optimal performance, choose trees, livestock and forages that are compatible with the site and with each other, that produce marketable products, meet landowner management objectives, and, if desired, provide wildlife or environmental benefits. Livestock in silopasture systems may include cattle, sheep, goats, horses, poultry, bison and elk.
During tree establishment, exclude livestock from the site or use electrified fencing to prevent damage to young trees. While livestock are excluded, you can still produce forage to sell or to feed livestock. Local Extension and Natural Resources Conservation Service offices are good sources of information about soil suitability for specific pasture and tree species.
Alley cropping
Alley cropping combines trees, planted in widely spaced single or grouped rows, with adjacent agricultural or horticultural crops cultivated in the wide alleys between the trees (Figure 2). Potential alley cropping species include fruit, nut, high-value hardwood veneer or lumber trees, or other fast-growing species such as hybrid poplar and red alder. You can cultivate annual crops such as row crops, forages and vegetables between rows of nut or fruit trees to provide extra income before the trees come into bearing.
As trees and shrubs grow, they influence light, water and nutrient regimes in the field. These interactions are what sets alley cropping apart from more common monocropping systems. Alley cropping provides an opportunity to convert marginal cropland to woodland while continuing to earn income from annual crops during the initial year of the planting.
Benefits of alley-cropping practices include:
- Increased income.
- Biological diversity.
- Improved aesthetics.
- A reduction of negative environmental impacts.
Alley-cropping practices are designed according to the site's characteristics, the tree products desired (nuts or timber), the growth requirements of the selected tree, the crop being grown in the alley, the farm equipment available and the landowner's objectives. For example, alleys can be arranged in straight rows and on diagonals to allow equipment to travel in various directions, improving access and reducing soil compaction. On sloping land, you may need to plant the rows on the contour, creating a terrace to reduce soil erosion due to water runoff.
While designs for an alley-cropping practice vary depending on landowner objectives, there are several basic considerations. Consider the spacing between the trees within the row and between the rows of trees. Selected trees should be deep-rooted, create a light shade, and produce one or more products (timber, nuts and fruit). The distance between the rows is determined by:
- Growth requirements of the companion crop.
- The width of the available farm equipment.
- The type of trees grown.
- The desired product or products.
The length of time the landowner wishes to grow a light-demanding crop in the alley. Shrubs or coniferous trees can be used in multiple rows to provide additional products and to train hardwood species to grow straight and tall, increasing their value as timber.
Growing trees for timber or nuts may require pruning of young trees. Pruning young nut trees to a height of 8 feet allows equipment to pass below the branches for mowing and harvesting while retaining much of the crown area. Greater pruning heights, to reduce defects in the wood caused by low branches, may be required for the production of quality timber.
Some producers plan alley cropping systems to provide additional functions that support and enhance other aspects of their operation. For example, a livestock producer might grow crops that supply fodder, bedding or mast crops for their livestock. Some producers may be interested in how alley cropping can support soil health. Other producers may want to produce biomass for on-farm use. Organic producers may choose tree species that fix nitrogen.
Farmers may also use alley cropping systems to transition from one farming system to another. The annual crops grown in alleys can provide short-term income until the trees are mature. The versatile nature of this practice allows a producer to react to markets, labor limitations and changing goals. Like all agroforestry systems, alley cropping systems should be considered as part of the whole farm operation.
Traditional row crops, as well as horticultural, medicinal and vegetable crops, can be incorporated into an alley cropping practice. As the trees grow and produce more shade in the alleys, you can choose different companion crops. Over time, competition for water can limit the width of plantings.
Deep trenching with a ripper, trencher or chisel plow between the tree row and the crop to sever lateral tree roots may be necessary to minimize production losses in alley crops. Wider alleys will accommodate crops that require full sun, such as corn and beans. When shade becomes limiting, shift to shade-tolerant forages or berry-producing shrubs.
Riparian forest buffers
A riparian forest buffer is an area adjacent to a stream, lake or wetland that contains a combination of trees, shrubs or other perennial plants and is managed differently from the surrounding landscape, primarily to provide conservation benefits. Riparian buffers consist of strips of perennial vegetation planted between crop or pastureland and streams, lakes, wetlands, ponds or drainage ditches.
Riparian buffers reduce runoff and nonpoint-source pollution from agricultural activities on adjacent lands by trapping sediment, filtering excess nutrients, intercepting and degrading pesticides and providing shade, shelter and food for fish and other aquatic organisms (Figure 3). They can also stabilize streambanks, protect floodplains and flood-control structures, enhance wildlife habitat and corridors, and provide a harvestable and salable product such as timber and pulpwood, fruits, nuts or floral products.
Riparian forest buffers can have positive impacts on water quality. One popular design consists of three zones (Figure 3):
- Zone 1, undisturbed or unmanaged forest, closest to the water
- Zone 2, managed nut or fruit trees and shrubs, next to the undisturbed forest
- Zone 3, managed woody florals and grasses, farthest from the water
The roots of the undisturbed vegetation (trees and shrubs) in Zone 1 stabilize stream banks and hold soil in place. Shade from the trees helps moderate the temperature of the water, benefiting aquatic life, including spawning areas for fish. Roots and woody debris provide food and habitat for aquatic life and slow the velocity of the water.
In Zone 2, the managed forest can be planted with fast-growing trees or shrubs that produce marketable products, which can be harvested for profit. In this zone, the soil absorbs nutrients in the runoff water, which are used by trees and shrubs. When flooded, forested zones also serve as recharge areas for groundwater aquifers, depending on the grade.
Grasses and other herbaceous vegetation in Zone 3 tend to increase soil porosity, allowing greater infiltration and water storage potential. Dense grasses slow the flow of surface water and spread water more evenly over the landscape. Reducing the velocity of the water allows sediment to settle out. It also allows time for pesticides to degrade and permits increased uptake of excess nutrients. Grasses can be used for forage, hay or other products.
Not all areas along a stream can accommodate these three zones. Allocation and implementation of these zones will depend on landowner objectives and state mandates and restrictions. Owners of nonfederal land in Oregon are subject to the Forest Practices Act and Rules.
The act restricts harvest activities within a certain distance of stream banks—, particularly where fish and domestic water supplies are involved, It also restricts the application of herbicides and fertilizer near streams. If your forest activities occur near a stream, see the Oregon Department of Forestry website to learn more about the Oregon Forest Practices Act and Rules.
Windbreaks
Windbreaks are plantings of single or multiple rows of trees or shrubs in farm fields to minimize damage from excessive wind. Windbreaks protect crops and livestock from strong winds, reduce wind erosion, improve irrigation efficiency, expand wildlife habitat, improve aesthetics, manage snow and provide marketable products (Figure 4). Windbreaks provide shade and protection from temperature extremes in pastures and around feedlots, improving livestock health, feeding efficiency and reproductive success. Increased plant and wildlife diversity can reduce fertilizer and pesticide inputs by increasing nutrient cycling and encouraging natural pest predators
Multiple-row windbreaks allow harvesting of marketable trees and products without reducing the effectiveness of the shelter. Windbreaks can also protect dwelling places from extreme winter winds. Producers select trees, shrubs or herbaceous vegetation both for the products they produce (nuts, pulp for paper, botanicals) and their effectiveness as windbreaks. Plants are placed perpendicular to the prevailing wind at wider spacing. Select species based on location, adaptability and marketability.
The area protected by and the effectiveness of a windbreak are determined by height, density, width, orientation, length and species composition. Wind speeds are reduced on the windward side of a windbreak to a distance of two to five times the height of the tallest row. On the leeward side, wind speeds are reduced for a distance of 10 to 20 times the height (H) of the trees. Windbreak density, the ratio of the solid portion to the total area (Table 1), determines the amount of wind that flows through the windbreak. Densities of 40% to 60% provide the greatest leeward area of protection.
Livestock windbreaks and crop windbreaks require different densities as well as orientations for optimal protection during sensitive seasons. Windbreaks are oriented perpendicular to hot, dry summer winds to protect field crops during the growing season, perpendicular to cold winter winds to protect livestock during calving season, and perpendicular to winter and early spring winds to reduce erosion when soil is exposed.
|
Distance from windbreak |
5H |
10H |
15H |
20H |
30H |
|---|---|---|---|---|---|
|
Miles per hour |
6 | 10 | 12 | 15 | 19 |
|
Fraction of open wind speed |
30% | 50% | 60% | 75% | 95% |
Adapted from the National Agroforestry Center
The most effective length of a windbreak is 10 times the height of the crop being protected. This length reduces the influence of turbulent winds at either end.
Avoid gaps in the windbreak; these create areas of high velocity that reduce its effectiveness of the windbreak.
Management is the key to an effective windbreak. Gaps resulting from tree harvest, damage or mortality must be replanted. You may need to prune your windbreak, either for timber production or for the general health of the trees and shrubs.
Windbreaks can also control the spread of pathogens and increase temperature and humidity on the leeward side of the trees compared with open ground during the early growing season.
For areas with heavy snowfall, windbreaks can function as living snow fences. They can capture and disperse snow more evenly across cropland and prevent drifting over roads and driveways. Shrubs or trees used in living snow fences and windbreaks should preferably include species that produce salable products, such as hazelnuts.
Forest farming
Forest farming is a unique practice in which existing forest stands are managed to create an appropriate environment for growing potentially high-value understory crops (Figure 5). Many medicinal and botanical plants currently harvested from wild sources on public and private lands are becoming scarce, making forest farming an important option for meeting demand for these plants. Forest farming can sustain overharvesting by managing for these scarce, high-value species.
Many crops can be sold for medicinal, ornamental handicraft or culinary uses. Shade-tolerant crops such as ginseng, goldenseal, wintergreen, bloodroot, decorative ferns, pollen, shiitake and morel mushrooms, as well as fruit and nut crops, can be intensively cultivated under a forest cover modified to provide the correct level of shade (Figure 5). Some existing practices combine growing ginseng, goldenseal and mushrooms, which have similar light requirements. Specialty products can also be produced in other agroforestry systems, such as windbreaks and forested riparian buffers.
Markets exist for many of these products, although they may be more typical of niche markets that can take some time to develop. Anyone interested in undertaking forest farming or producing special forest products should thoroughly research the crop, its growing requirements, the markets available and the potential for developing markets. Depending on the crop and the production and marketing skills of the landowner, forest farming can provide considerable regular income either before or as an alternative to harvesting the trees for wood products.
These practices are relatively labor intensive compared with typical agriculture and forestry practices. It is always a good idea to start small to see if the practice will actually meet your objective.
For more information
Angima, S. 2009. Forage production under thinned Douglas-fir forest. In Proceedings of the 11th North American Agroforestry Conference, ed. M.A. Gold and M.M. Hall, 421–426. Columbia: University of Missouri Center for Agroforestry.
Garrett, H.E., W.J. Rietveld and R.F. Fisher, eds. 2000. North American agroforestry: An integrated science and practice. Madison, WI: American Society of Agronomy.
Josiah, S.J., L. Gordon, E. Streed and J. Joannides. 1999. Agroforestry in Minnesota: A guide to resources and demonstration sites. St. Paul: University of Minnesota Extension Service.
Peters, S.M. 2000. Agroforestry: An integration of land use practices, ed. S.S. Hodge. Columbia: University of Missouri Center for Agroforestry.
Tamang, B., D.L. Rockwood and M.G. Andreu. 2009. Microclimate modification by tree windbreaks in Florida farms. In Proceedings of the 11th North American Agroforestry Conference, ed. M.A. Gold and M.M. Hall, 413–420. Columbia: University of Missouri Center for Agroforestry.
Orefice, J., M.M. Smith, W.C. Weinberg, et al. Carbon dynamics of silvopasture systems in the Northeastern United States. Scientific Reports 15, 6995 (2025).
Castle, S.E., D.C. Miller, N. Merten, et al. Evidence for the impacts of agroforestry on ecosystem services and human well-being in high-income countries: a systematic map. Environmental Evidence 11, 10 (2022).
Smith, M.M.; G. Bentrup, T. Kellerman, K. MacFarland R. Straight, L. Ameyaw. Agroforestry Extent in the United States: A Review of National Datasets and Inventory Efforts. Agriculture 2022, 12, 726.
USDA, 2024. Agroforestry Strategic Framework
USDA – Agroforestry
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