Agroforestry is an intentional growing of woody plants with row crops, forages and/or livestock.  Practiced in various forms since ancient times in China, the Mediterranean, and pre-colonial America, agroforestry is now gaining interest in North America because of associated economic and environmental benefits.  At UF/IFAS North Florida Research and Education Center (NFREC), there is an active research and extension program in silvopasture, which is one of the six major agroforestry practices (see below).

Economic Benefits 

The economics of agroforestry rely on the premise that while it usually takes years for the woody crop to mature, associated crop(s) and/or livestock can provide annual income in the interim. 

Environmental Benefits 

Trees in agroforestry systems modulate microclimate, improve nutrient and water relations, prevent soil erosion and provide habitat for wildlife and other desirable organisms.  In some documented cases, diverse woody and cover crop species combinations provided habitat for beneficial insects, which were either pollinators or known biological control agents for pest species.  Agroforestry systems with livestock can have higher nutrient use efficiency and turnover rates compared to other production systems. 

Major Agroforestry Practices 

Agroforestry is an umbrella term for at least six major practices:

• Alley Cropping

• Forest Farming

• Riparian Forest Buffers

• Silvopasture

• Windbreaks

• Special Applications

Alley Cropping 

Alley cropping consists of planting other crops between widely spaced rows of trees or shrubs.  The alleys should be wide enough for farming with standard agricultural equipment.  Cash crops most often grown in the alleys are hay, corn, cotton, watermelon, squash, other vegetables, berries or Christmas trees.  The growing demand for medicinal and other specialty crops such as ginseng, ethnic vegetables, and herbs, may provide additional species for alley production.  Preferred woody species are southern pines, pecan, ash, oak, persimmon, cherry, poplar, blueberry or ornamental shrubs.  The level of shade provided by trees increases over time, so the alley crop should be changed periodically to match the changing environmental conditions. 

To establish an alley cropping system, trees can be planted or thinned to single or multiple rows and used for pulpwood, firewood, or fence posts at a young age.  The ultimate wood production objective should be large diameter sawtimber, or other high-value timber products depending on local market conditions. 

Forest Farming and Non-Timber Forest Products (NTFPs) 

Forest farming utilizes forested areas for producing specialty crops that are sold for ornamental, culinary or medicinal uses.  Specialty crops that tolerate partial shade include wildflowers, herbs, saw palmetto, ferns, mushrooms (e.g., morels and shiitake), fruits (e.g., plums, pawpaw, mayhaw, wild berries).  Other non-timber products that can be collected and marketed are honey, pine straw for mulch, and crafting materials.  Intentional management for the specialty crops that include overstory tree manipulation can increase the overall system productivity and profitability. 

Forest farming is practiced successfully all over the world.  The multi-storied nature of these systems allows for cultivation of different crops at various layers.  For example, below-ground root crops, herbaceous ground covers, shrubs, understory trees and trees in the main canopy can all be part of one forest farming operation. 

Riparian Forest Buffers 

Riparian forest buffers are already a common practice in the Southeast as a result of limited timber harvesting along streams and other water bodies.  These buffers, also known as Stream Management Zones, or SMZs, are mandated by each state’s Silvicultural Best Management Practices (BMPs).  Riparian forest buffers, whether natural or designated, have a dominant woody component, which sets them apart from “vegetative filter strips” that are used to intercept surface runoff in agricultural settings. 

Riparian forest buffers filter and trap runoff sediment, slow down flood flows and provide waterbreaks in floodplains.  Most of all, under anaerobic conditions and in the presence of organic matter, these riparian forest buffers can remove large amounts of nitrate from shallow groundwater by a process called denitrification.  During this process denitrifying bacteria convert dissolved nitrate to nitrogen gases, which are then released to the atmosphere. 

Silvopasture 

Silvopasture intentionally combines timber with livestock and forage production.  In the Southeast, good growing conditions can be maintained for both timber and livestock on the same site through the length of the timber rotation.  To achieve that, trees are planted or thinned in ways to provide sufficient light for good forage growth.  Southern pines can be intensively managed in single widely spaced rows, or grouped in double or triple rows to improve stem form, with wide forage alleys between the tree row sets.  Systems with bahiagrass as a summer forage and clover, ryegrass or rye as winter forage are the most common.  Silvopastures currently in use incorporate rotational grazing with cattle, goats or sheep.  Studies from across the South (e.g., Louisiana, Mississippi and Georgia) report the possibility of productive livestock grazing while maintaining or improving high-value timber production.  Under most economic conditions, cash flows generated by silvopastures compare favorably with that of timber-only operations. 

Current silvopasture research at NFREC tests different summer and winter forage combinations under thinned loblolly pine canopies.  Bahiagrass forage yield in newly established longleaf pine-based silvopastures is also measured and compared to conventional pastures. 

Windbreaks and Linear Border Plantings 

Windbreaks are rows of trees and/or shrubs around homesteads, farms, and fields that are managed as part of crop or livestock operations.  They modify microclimate and are most effective against wind-caused soil erosion.  In addition to soils, windbreaks protect livestock and crops, help reduce dust, odor, and noise; and provide cover and food for wildlife.  In the South, effective windbreak tree species include pines, eastern redcedar, cottonwood, boxelder; and shrubs such as hollies, crabapple, hawthorns, laurelcherry, and flowering ornamentals. 

Special Applications 

There are a number of agroforestry practices that can be termed special applications, because they escape one common name or purpose.  Overlaps of structure and/or function between special agroforestry applications and previously described practices may exist.  For example, linear woody landscape corridors for wildlife habitat and movement may be very similar to windbreaks in their structure and function, if not localization on the farm.  Another example of special application is the production of short rotation woody biomass (e.g., poplars, eucalyptus) as a component for treatment of animal waste lagoons.  Fruit orchards in the establishment phase can be used for intercropping forage, row, or vegetable crops during the first few years after planting.  Grapes have been combined with vegetable production.  Honeybees have long been placed in vicinity of citrus orchards and on farms for pollination.  In addition, edible landscape plants and multi-strata patio, or home gardens, are increasingly popular. 

Unanswered Research Questions 

• What are compatible crop/forage rotations with which tree/shrub species?

• What are the yields in different species/rotation combinations?

• What are optimal tree/shrub spacings for different practices and species combinations?

• How to best control weeds, especially at crop/tree/shrub row interfaces?

• What are the optimal components of the integrated pest management?

Technology Transfer Needs 

• Management guidelines for different agroforestry practices

• Marketing information for less common commodities

• Financial analysis models for different practices

• Plant material and availability information.

For more information on agroforestry in Florida and the Southeastern U.S. visit the Center for Subtropical Agroforestry (CSTAF) website (http://cstaf.ifas.ufl.edu/) at the University of Florida/IFAS, or call (850) 875-7145.  [Minogue, P., pminogue@ufl.edu]

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