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Agroforestry: trees, bushes, crops and intensive grazing

By Juan P. Alvez, Pasture Program Technical Coordinator,
Center for Sustainable Agriculture, UVM Extension

Added December 9, 2013. Forests are a tremendous natural asset and they cover over 75% of Vermont’s territory. Keeping the land “open” is sometimes a challenge. Still, much can be done to diversify farms, generate income and protect the environment. Agroforestry may be the answer.

Agroforestry offers multifunctionality and resiliency to constitute one of the most sustainable agricultural practices;, integrating trees, crops and animals in the same area and at the same time, or in a time sequence. It can either combine one or two tree species with annual or perennial crops in different arrangements (alley cropping, hedgerows, windbreaks, etc.). They can serve multiple objectives associating, grazing, annual/perennial crops, timber, fruits, nuts and medicinal products for humans and livestock, stream bank protection and habitat for wildlife in the short, medium and long term.

For instance, integrating grazing animals with a maple “sugarbush”, gives animals access to valuable forage plants while they control invasive species and build soil fertility. RAlso, riparian systems that include mixed productive species can greatly contribute to stream bank protection and improve water quality. They can also provide numerous other benefits for farmers (including forest products, flood, erosion and sedimentation control), and for nature (providing habitat for wildlife, a healthier local ecosystem, and a pleasant landscape). Other examples of productive forests include coppicing, biomass, biofuel and mushroom production.
Agroforestry systems can be categorized in agro forests, or a combination of trees and crops; silvopastoral systems (silvo: trees; pastoral: grazing animals), where trees and grazing animals interact in the same area, and agrosillvopastoral systems, where grazing animals and crops are combined in rotation with trees.

Benefits and weaknesses

There are several advantages of agroforestry systems. Because its principles mimic natural systems, it generates greater resiliency or rebounding capacity when exposed to external impacts such as weather or market fluctuations.

  • Soil fertility. Most trees can draw nutrients deeper by cycling them when shedding their leaves in the fall. Because trees are not annual crops, surrounding soils remain undisturbed. No-till crop agriculture helps conserve soil and Intensive rotational grazing management in alleyways can help recirculate nutrients through the grazing animals’ urine and manure. Alleyways must be adequately wide to allow sunlight and machinery.
  • Improved soil and water quality. Covered soils are key for improving water quality and along with crop rotation it reduces sediments.
  • Climate regulation. Trees can sequester and store carbon in their tissues through photosynthesis. Intensive grazing management also helps regulate climate by letting forage plants rest and store energy in the form of carbohydrates (sugars) in their roots.
    Higher production and net profits per area. The multifunctionality of agroforestry systems allows for a multilevel agriculture, increasing products and income per area.
  • To gain maximum benefits for both farmer and the environment, agroforestry systems must be planned for the short-, medium- and long-term. Crops and animals can provide short and medium term gains. Some non-timber forest products can be harvested periodically while, in the long run, highly valuable timber products can be managed to complement retirement earnings serving as a retirement supplement.
  • Connecting forest patches and acting as wildlife corridors.
  • Single or multiple species can be used; however, different species can help minimize risks and add more economic and environmental sustainability over time.
  • The diversification of AFS can lower market and weather risks because more integrated products and services are farmed.

Among its disadvantages are:

  • The necessary knowledge about all involved species and the complexities of how it works in a given region.
  • Labor and initial investment costs can be an issue especially establishing AFS.
  • Management of different activities can be overwhelming.
  • The growth time of some species can be a determining factor for the success of AFS.

Different Agroforestry Arrangements

Silvopasturing

Windbreaks

Windbreaks. Protect crops from prevailing winds facilitating pollination, increasing soil moisture, production and reducing wind erosion. Windbreak yield efficiency increases 5-45% with the use of multiple species at different heights.

Alley cropping. Trees are arranged in rows where crops are placed in wide alleyways in-between. Hay or grazing animals can be also intercropped along the alleyways.

Silvopasture. Combination of trees, forages and livestock. Trees can be arranged in a scattered or in a row (or alley cropping) fashion. Ideally, animals must be rotationally grazed and must be introduced into fenced in areas of the system when trees are strong enough to withstand their presence. Animals and forage benefit from shade and shelter, while trees and forages cycle animals’ manure.

Riparian buffers. Provide river bank protection by reducing erosion and increasing ecosystem conservation in waterways enhancing water quality. If regulations permit, productive species can be planted along riparian buffers with the potential to offer extra income from fruits or fuel.
Forest Gardens. Integrate food, herbal, timber and non-timber forest products in the same area allowing for sustainable income.

Wildlife corridors. As forest and ecosystems become more fragmented by human activities, it is important to consider rotating fallow areas and leaving “corridors” for connecting forest and grassland patches. They help rebuilding wildlife habitats playing an essential role in ecosystems.

Islands of high biodiversity. Recently implemented in Brazilian Atlantic Forest, has the potential to reforest previously denuded areas with native productive species.

Living posts, living fences or hedgerows. Can serve multiple purposes such as, containing animals, aesthetically pleasant windbreaks, wildlife corridors and productive crops.

Some species suitable for the Northeast

Trees: Alder, Ash, Black Locust, Honey Locust, Poplar, Chestnut, Oak, Willow, Hickory, Hazel, Hawthorn

Bushes, berries and fruit trees: Cherries, Mulberry, Elderberry, Serviceberry, Cranberry, Raspberries, Blueberries, Paw-paw, pear, apple, plums.

Resources and references

Alavalapati, J. R. R., R. K. Shrestha, G. A. Stainback, and J. R. Matta. 2004. Agroforestry development: An environmental economic perspective. Agroforestry Systems 61 (1):299-310.
APREMAVI 2013. Sistemas Agroflorestais. On-line: http://www.apremavi.org.br/cartilha-planejando/como-fazer-sistemas-agroflorestais/

Ares, A., and D. Brauer. 2005. Growth and nut production of black walnut in relation to site, tree type and stand conditions in south-central United States. Agroforestry Systems 63 (1):83-90.

Bhagwat, Shonil A., Katherine J. Willis, H. John B. Birks, and Robert J. Whittaker. 2008. Agroforestry: a refuge for tropical biodiversity? Trends in ecology & evolution 23 (5):261-267.

Casals, P., T. Baiges, G. Bota, C. Chocarro, F. de Bello, R. Fanlo, M. T. Sebastia, and M. Taull. 2009. Silvopastoral Systems in the Northeastern Iberian Peninsula: A Multifunctional Perspective. Agroforestry in Europe: Current Status and Future Prospects:161-181.

Nair, P.K.R. 1993. An introduction to agroforestry. Dordrecht, The Netherlands: Kluwer Academic Press/ICRAF.

Nair, P.K.R., R.J. Buresh, D.N. Mugendi, and C.R. Latt. 1999. Nutrient cycling in tropical agroforestry systems: myths and science. In Agroforestry in sustainable agricultural systems, edited by L. Buck, J. P. Lassoie and E. C. M. Fernandes. Boca Raton, FL, USA: CRC Press.

Training Manual for Applied Agroforestry Practices - 2013 Edition. University of Missouri Center for Agroforestry. On-line: http://www.centerforagroforestry.org/pubs/training/index.php

Juan P. Alvez joined the UVM Center for Sustainable Agriculture in 2012. He comes from a two-generation pasture-based farm in Uruguay. He obtained his BS in Agronomy in Brazil, and both his MS and Ph.D. at the University of Vermont, in Plant and Soil Science and Natural Resources respectively. His work addresses environmental, social and productive aspects of grazing farms, with emphasis on dairy management, ecosystems conservation and sustainable livelihoods in Vermont and New England. Contact Juan by email or phone: 802-656-6116; jalvez@uvm.edu.

 

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