What is Agroforestry?

Agroforestry is...

"The intentional integration of trees and shrubs into crop and animal farming systems to create environmental, economic, and social benefits. It has been practiced in the United States and around the world for centuries."

     - United States Department of Agriculture

Benefits

• Diversified income sources

• Improved soil health

• Improved water quality

• Wildlife habitat

 

Potential Benefits

• Nutrient retention

• Landscape & biological diversity

• Carbon sequestration

• Visual quality

The Four I's of Agroforestry

Intentional: The combination of trees, crops, and/or animals is purposefully designed as a whole system.

 

Intensive: Agroforestry systems are  managed to maintain high levels of productivity and functions with minimal input.

 

Integrated: All aspects of the system (trees, crops, animals) are thought of as a series of components working together in horizontal and vertical space as well as above and below ground.

 

Interactive: Managers are actively working with agroforestry systems to optimize biological interactions between trees, crops, and animals.

Alley cropping system with black walnut with corn

Where does agroforestry come from?

Diverse food producing systems originated in the tropics where trees are a necessity to preserve soil quality and increase nutrient cycling. These systems still remain popular with many cultures living in forested areas. Groups like the World Agroforestry Centre actively work to promote diverse woody systems in these regions for increased agricultural sustainability but have yet to extend their work into temperate regions, such as areas like the Midwest.

 

Traditionally,  woody crops were commonplace in agriculture up to the 20th century by both indigenous peoples and European Settlers. They were used as windbreaks, buffers, or simply for food and timber. As policy changed and technology progressed, row crops began to populate the rural landscape. The use of trees was forgotten. However there is now a resurgence of interest in temperate agroforestry to increase agricultural sustainability while still producing adequate, nutritious food.

Alley cropping system with wlack walnut with corn

Types of Agroforestry Systems

Agroforestry systems vary by region, farmer, crops, and goals. Below are five of the most common practices found in the temperate region today.

Forest Farming

The oldest form of agroforestry, where high-value crops are grown underneath a forest canopy modified for a specific mode of production (timber, fruit, or nut). Shade tolerant species such as mushrooms and herbs grow well in these areas.

Silvopasture

The practice of intentionally combining livestock grazing and trees. The trees are used for timber or food crops and provide animals with shelter, shade, and forage. Animals can provide short term income while longer term tree crops mature and accrue value.

Alley Cropping

The planting of rows of trees with wide spacings to allow alleyways of agricultural/horticultural crops to be grown in between. Plants can also be grown within tree rows. Tree crops provide long term income and shelter  while alley crops provide immediate value.

Riparian Buffers

These are a diverse assemblage of plants that border a body of water and agricultural area. The woody buffers reduce runoff, non-point source pollution, and soil erosion, while providing wildlife habitat. These systems can ideally produce food/timber as well.

Windbreaks

Traditionally common in the Midwest, windbreaks  are planted to provide barriers for livestock or crop production. They can reduce wind speeds, snow drift, soil erosion, and provide wildlife habitat. Windbreaks can be managed for timber, and/or fruit & nut crops.

Resources

Five agroforestry practices: University of Missouri Center for Agroforestry Publications (http://www.centerforagroforestry.org/pubs/training/index.php)

Forest farming photo: Alllerton Park (http://allerton.illinois.edu/wp-content/uploads/DSC01122-608x456.jpg)

Riparian buffer photo: http://www.ia.nrcs.usda.gov/news/successstories/successstories.html

Multi-dimensional Space

One of the primary objectives of agroforestry systems is to capture more light and nutrients by occupying multiple vertical and horizontal spaces relative to monocultures. In the diagram to the right, it can be seen how a variety of species can occupy all potential spaces in a given area and maximize production in them. The distinct layering of canopies has the potential to maximize light capture and plant utilization by reducing the amount of light lost to the soil or the atmosphere that occurs in single layer systems. The combination of a variety of species also means that root system architecture would ideally vary to reduce below ground competition and uptake more nutrients. By critically studying how species selection and spacing affects resource capture, we can work towards creating an "optimized" agriculutral system for the future.