What is Agroforestry?

Integrating the best trees for silvopasture into agroforestry can improve your farm’s efficiency and soil quality.

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by AdobeStock/paparadox

I once rented a pasture that adjoined a yard containing two apple and two pear trees. Every fall when the fruit ripened, the loaded trees would drop any blemished fruit early. The homeowner hated mowing around the fallen fruits, and my cows liked to eat the ones that rolled across the fence, so when they were in the adjacent paddock, I’d throw the windfall fruits across the fence. At other times, I’d fill my pickup bed and drive the fruit to where the cows were. It was a great win-win method to clean up the yard and give my cows a treat at the same time.

But it was also time-consuming and backbreaking work. Instead of doing all this work, I thought, what if I planted apple and pear trees right where I needed the fruit to be: in my pastures? They could give my cows shade in summer, fruit in fall, and fallen leaves in winter as forage. Instead of just four trees for the entire herd, I could have a tree spaced every 30 or 40 feet on a grid, 30 or 40 trees per acre. Now that would feed a lot of cows!

This idea isn’t new — in fact, I read a book when I was in college that completely altered my view of what the future of agriculture could be. The book, Tree Crops, was written by geographer J. Russell Smith, who traveled around the world and took note of the conditions of both soil and society in a number of different areas. He observed the devastating soil erosion associated with annual grain crops and, in contrast, the food systems based on trees that dropped fruits and nuts that were harvested by either humans or livestock. Smith noticed that societies based on tree crops were prosperous and long-lived and didn’t require the backbreaking work associated with growing annual grain crops. In addition, the soil was held intact by the trees and didn’t require land-ruining tillage.

Imagine how different our country might be if the 95 million acres of corn and the 90 million acres of soybeans were instead in a mixture of grass and trees, dropping feed freely picked up by livestock.

Agroforestry in a Nutshell

Agroforestry is perhaps easier to explain if we start with forestry. Forestry is essentially the cultivation of trees, usually intended for timber harvest. It’s often the sole enterprise on many timbered lands. Agroforestry, on the other hand, is the culture of trees integrated with other forms of agriculture, such as pasture or crops.

Agroforestry has many advantages over simply using the land for a single purpose, whether that purpose is forestry, livestock, or crops.

  • The vegetation can capture sunlight over multiple layers and for an extended season, offering more productivity and, ultimately, better soil.
  • Tree canopies can protect underlying crops and animals from sun and wind.
  • Tree roots and herbaceous plants underneath can combine to reduce soil erosion from either wind or water.
two illustrations showing a square area cut out of a forest and strips cut through forests
  • Increased plant diversity can reduce the risk that a disease or insect can take out the entire crop. At the same time, that diversity will attract a wider range of benign insects, which will attract insect predators that, in turn, can control future pest insects.
  • The risk of low prices for any one enterprise is reduced; the portfolio will be more balanced.
  • Diversity of crop roots and the extended duration and increased rate of photosynthesis can improve the rate of carbon sequestration in the soil compared with that of forest, grass, or cropland.

Primary Forms of Agroforestry

Riparian Buffers

By protecting the banks of streams and rivers from soil erosion, riparian buffers not only save soil from being lost, but they also reduce the amount of pollution in water from soil particles, pesticides, and fertilizers. A properly designed riparian buffer should consist of trees, shrubs, and herbaceous vegetation to fully protect soil and water.

You can select species of trees to provide a harvestable crop, such as maples for syrup or walnuts or pecans for nuts and timber. Many high-value trees, such as black walnuts and pecans, are natural inhabitants of riparian areas.

illustration showing the side of a riparian buffer with a lake, shrubs, trees, brush, grass, and crops going left to right

Windbreaks

Valuable in countless ways, windbreaks can be used to protect homes, crops, or livestock. Their design — the location, spacing of trees, and number of rows — varies depending on the intended purpose.

Home protection. In areas with cold winds and winter snow, windbreaks trap snow, reduce wind velocity around homes, and reduce home heating costs.

Livestock protection. Windbreaks for livestock can greatly reduce winter feed needs and improve comfort, as well as reduce animal mortality from blizzards. Design them perpendicular to prevailing winter winds and on the windward side of the animals.

Crop protection. For crops, windbreaks are usually placed on the windward side of prevailing hot summer winds. Sometimes, trapping snow is important for increasing moisture supply; for this, build windbreaks on the windward side of the prevailing winter winds.

illustration showing trees acting as a natural windbreak with arrows showing wind movement towards a house being interrupted by trees

Forest Farming

The cultivation of crops that thrive in a forest environment is called “forest farming.” One of the best-known high-value forest products is maple syrup. Many other trees, such as birch, sycamore, walnuts, and hickories, can also be tapped for sap that can be boiled down into syrup, each with its own unique flavor.

Other examples of forest crops are medicinal plants, such as ginseng, black cohosh, and goldenseal; mushrooms, such as shiitake; and fruits, such as pawpaw and currants. Truffles are an underground fungus of particularly high value.

Alley Cropping

Common in tropical areas, alley cropping is the practice of planting widely spaced rows of trees with rows of crops in between. It can be a long-term strategy or a transitional stage into silvopasture to protect small trees that can’t withstand livestock browsing or rubbing.

Alley cropping can benefit row crops by protecting them from wind, especially in areas where sandblasting of crops is common because of windblown soil, or where evapotranspiration is high because of frequent strong winds. In tropical areas, alley cropping involves leguminous tree rows alternating with annual crops. The farmer cuts off the tree branches after the crop is established and uses them as a mulch between the crop rows to protect the soil and release nitrogen as it decays. This is a useful practice where nitrogen fertilizer is expensive and hard to obtain.

Alley cropping also offers multiple land management benefits. The basic configuration — the “corrugated canopy” of alternating tall trees and short crops — captures sunlight efficiently for high biological productivity. The ground-level (often annual) crops are productive in the short term and help the land provide immediate returns, while the trees are a long-term crop that may take several years to become profitable. Other benefits include shade for livestock, windbreak capacity, and increased biodiversity.

illustration of alternating rows of trees and crops

Benefits of Silvopasture

The integration of trees and pasture, silvopasture essentially mimics a savanna, an ecosystem that arguably produces more animal biomass per unit of land area than any other on Earth. (African savannas — those that still exist — host spectacular animal populations.) You can create a silvopasture by adding trees to a pasture, or by adding herbaceous vegetation (grasses, legumes, and forbs) to a forest.

The incredible potential productivity of a silvopasture arises from a few different factors.

Sunlight Capture

Trees and pasture together can capture sunlight over a longer duration than either can alone. For example, a field of evergreen pine trees with an understory of warm-season grasses will photosynthesize at a high rate both in summer (because of the efficient photosynthetic capacity of warm-season grasses) and in winter (from the pine trees that keep their leaves or needles in winter).

A combination of deciduous trees and cool-season grasses takes advantage of the trees getting first use of the light in the summer, with shade-tolerant grasses underneath. The trees drop their leaves and allow more light to reach the grasses during winter, when sunlight is less direct and available.

Animal Productivity

Silvopasture can protect animals from intense heat and sun in summer and from wind in winter. Research in Kentucky has indicated that shade can increase animal performance to a remarkable degree in the summer in humid areas, increasing average daily gain on beef steers by 1.25 pounds of liveweight.

Additionally, wind protection can increase animal performance in winter.

Specific tree species can provide dropped leaves, fruit, or nuts in fall for supplemental livestock feed.

Plant Diversity

A diversity of plants can confer countless benefits.

  • Diversity reduces disease and insect pressure on any one species of plant.
  • The mix of roots, root exudates, and vegetative material returned to the soil increases soil development and productivity.
  • Woody debris and fallen leaves are particularly valuable for the development of soil fungal populations, while herbaceous perennial plants are also highly beneficial to soil.
  • A combination of grasses, legumes, forbs, and trees can build soil much faster than any of the components individually.

Some species of trees, such as oaks and pines, host ectomycorrhizal fungi, which are different from the endomycorrhizal fungi hosted by most herbaceous plants; the former can bore into the rocky soils that characterize many pastures and extract water and nutrients from the soils. This explains why many rocky areas are dominated by oak and pine trees. The cycling of the nutrients thus extracted and contained in needles, leaves, and acorns can help enrich soils beneath them to the benefit of the other plants.

Silvopasture Management

Because silvopasture management must take into account the needs of pasture, trees, and animals, it demands more thought than most land use. That means more careful planning, closer monitoring, and more ongoing maintenance.

Protection of trees from animals. When trees are small, they may require protective structures to prevent animals from browsing and rubbing on them. Rotational grazing may also be essential to minimize damage to trees and tree roots. Incorporate tree lines into electric fence lines of paddock subdivisions to manage the fencing and minimize livestock eating and rubbing on trees.

Choose shade-tolerant forages (that are fairly non-competitive with the trees). Among warm-season grasses, Eastern gamagrass is more shade-tolerant than most other species. Among cool-season grasses, Virginia wild rye is shade-tolerant but may be less productive than other species, such as low-alkaloid reed canarygrass or orchardgrass. Kura clover (or AberLasting clover, which is a hybrid of kura and white varieties) is a star legume; subterranean clover is also good.

Control of competitive plant species. Tall fescue and smooth brome are notorious for being competitive with trees, especially in early development. This isn’t to say that these species can’t be used in a silvopasture — and they may have advantages that other forage species don’t — but you need to manage them.

For example, maintain a grass-free area around the bases of the trees, or plant shallow-rooted white clover (or maybe currants, ginseng, or goldenseal) for a higher-value, shade-tolerant crop. Grass can be selectively removed from broadleaf plants or legumes with the herbicide Clethodim, if the landowner isn’t opposed to herbicides.

illustration of a three section silvopasture farm plan with different trees in each section

My Dream Silvopasture Farm

I’ve sat down many times over the years to sketch out an ever-evolving plan for my future silvopasture farm, which includes three distinct pasture types. You can use these plans to inspire your own!

Warm-Season Grass Pasture

The understory would be composed mainly of Eastern gamagrass, along with alfalfa (lucerne), chicory, plantain, Maximillian sunflower, Korean lespedeza, crabgrass, and a host of other native warm-season grasses, wildflowers, and legumes, with a willow and mulberry overstory. The grasses would provide summer grazing for the livestock, with the high-protein willows providing browse and picking up the slack in late summer as the grasses decline in productivity.

The trees would be planted north-south to allow the prevailing summer wind to blow between them and provide shade throughout the day.

The mulberries would provide summer fruit for pigs and excellent browse for beef animals. Other summer fruits, such as gooseberries, currants, goumi, Lodi apples, apricots, and wild plums, could extend the fruit drop for the pigs.

Winter Pasture

Friendly endophyte tall fescue, red clover, bird’s-foot trefoil, and small burnet — all of which retain their quality well into the winter months — would be planted under east-west lines of pines to block the cold north wind. Winter-hardy bamboo and shrubs that retain their leaves in winter, such as fourwing saltbush, could also be incorporated.

Widely spaced, thornless honey locust trees would drop high-sugar pods that persist on the ground with minimal deterioration in the winter, providing a high-energy supplement for wintering cattle. Blocks of pines in the southeast corner of each paddock would offer emergency shelter from blizzards.

Spring-Fall Pasture

A blend of cool-season grasses, forbs, and legumes, such as low-alkaloid reed canarygrass, meadow brome, orchardgrass, smooth brome, alfalfa, red clover, white clover, bird’s-foot trefoil, chicory, and plantain would be planted under a diverse blend of oaks and chestnuts for high-carb nuts, as well as hazelnuts, walnuts, and pecans for high protein. Additional trees might include autumn olive, apples, pears, and persimmons for high-energy fruits.

This field can be pastured primarily in spring and fall, with an abundance of pig food in fall and fruits relished by cattle. The deciduous trees’ leaves will add to the cattle feed supply in fall.

These three pastures provide nearly year-round grazing for cattle, even during heavy snow cover, and fruits and nuts to feed pigs (or poultry). No diesel, no fertilizer, no work beyond that done by cows and pigs. The whole farm runs on sunshine, and every year, the soil gets better.


Excerpted from The Complete Guide to Restoring Your Soil © 2021 by Dale Strickler. Used with permission from Storey Publishing.