Sustainable Agriculture and Silvopastoralism

Silvopastoralism:
the complementary relationship between trees and pasture in a forest products and livestock production system.    Silvopasture practice takes many forms and is adaptable to a variety of smallholder farms and pastoral systems throughout the world.

    Sustainable agricultural practices such as agroforestry will provide the maximum benefits for humans, livestock, and crops, while striving for the least disturbance of wildlife and the natural ecosystems on which they depend.  Agroforestry is a relatively low-input integration of trees into crop and pasture systems.  Its implementation is of great value in developing countries of the tropics, where people are being driven onto marginal lands by poverty and inequitable land distribution.  These marginal lands are critical to wildlife and the preservation of watersheds but are being rapidly deforested to grow crops.  This practice leads not only to loss of the forest resource, but to the loss of the soil resource through erosion, damage to watersheds, and to a widening spiral of poverty for the poor people of the world.
    One type of agroforestry is silvopastoralism, which focuses on the production of livestock and tree products in one integrated pasture system.  Silvopasture is big business in the Southeast of the United States where it is economical to run a single species, cattle, under a pine monoculture in a large silvopastoral operation. However, on small farms, especially in the tropics, diversification through managing a variety of both animal and plant species is the most efficient utilization of the resource, and provides a variety of products, thus providing a hedge against risk.
Photo courtesy Cornell University
 
 
 
 
 
 
 
 
 
 
 

In a silvopastoral system,
trees may be planted in pastures
in a variety of spatial patterns...
Photo courtesy Dr. Jim McAdam at The Irish Scientist
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

...or an existing woodland may be thinned to reduce canopy and encourage growth of forage species in the understory.
Photo courtesy USDA National Agroforestry Center
 
 
 
 
 
 
 
 
 
 
 
 

The many benefits of silvopasture include:

Increased income opportunities through diversification of production

    A silvopastoral system, in addition to producing forage for livestock, may produce sawtimber, pulpwood, posts and poles for fences and other structures, and non-timber forest products such as nuts, fruit, honey, maple sugar, mushrooms, fodder, and materials for crafts. Livestock on silvopasture can be domestic mammals such as cattle, bison, sheep, goats, hogs, llamas, or horses, or domestic birds such as chickens, ducks, geese and ostriches.  Wildlife such as deer and elk will also benefit from silvopasture and can bring in income from hunting. Animal species provide a wide range of products including wool, feathers, leather, meat, milk, and eggs.
 
 
 
 
 
 
 
 

Enhancement of economic performance
Photo courtesy USDA - NRCS
    Silvopastoral systems provide a relatively quick return on investments in livestock and a long-term source of income in tree crops.  While timber offers higher returns, it is many years before those returns are realized.  Livestock provide yearly cash flow between timber harvests.
    Because of the differences in preferred forage among species, a mixture of livestock can use the forage resource more efficiently.  In addition, livestock grazing is a biological weed control, thus decreasing the need for herbicides.  The diversity of both forest and range products help to reduce risk to the agricultural producer.
 
 
 
 
 
 
 
 
 
 

Reduced climate-induced stress to livestock
Photo courtesy USDA - NAC

    Winterkill from exposure to severe weather is a major source of livestock loss, not only in the developing world but in the United States as well.  Shelter for livestock is needed in severe weather events, but unfortunately in many locales such shelter is lacking. Stress to livestock can be reduced through moderation of the pasture microclimate that a well-planned silvopastoral system provides.  Windbreaks, living snow fences, and outdoor living barns reduce windchill stress and divert snow away from livestock feeding and calving grounds.
 
 
 
 
 

 Enhanced wildlife habitat

    Cover and food for wildlife is provided by structural and species diversity of the tree and shrub overstory. Forest/grassland edges attract a variety of species such as deer and upland game birds.  Plant species may be manipulated through carefully managed grazing and timber harvesting to attract desirable wildlife species.
 
 
 
 

Improved soil conditions
Photo courtesy USDA - NAC

    Trees hold nutrients in an efficient, closed cycling system. Their deeper roots tap nutrients from lower soil levels that are inaccessible to forage species, and nitrogen-fixing trees can raise the nutrient levels of pasture soils.  Roots combat the compaction of soil and cut soil and organic matter losses to erosion, thereby improving soil structure and soil biological activity. Shade and reduced wind velocity raise the moisture level of soils by reducing evaporation. Trees planted in a living snow fence can raise soil moisture by harvesting and distributing snow. Some species can remedy soil toxicities that limit livestock forage production, such as salinity.
 
 
 
 
 
 

Planning a silvopastoral system


Image courtesy USDA National Agroforestry Center
Well-planned location and spatial pattern of tree plantings can meet many needs in a silvopastoral system.  In addition to deciding which species will provide the desired products, the agroforester must consider how the pattern of trees affects wildlife habitat, ease of livestock handling, forage and tree growth and competition, snow distribution, and microclimate.
 

From the bottom left and moving counter-clockwise, the image shows the following silvopastoral practices:

Continuous even spacing that optimizes light and growing space for both forage and timber.  The number and size of trees should be managed for optimum forage production while keeping in mind how the spacing affects tree growth and competion with one another. The thinning treatment is similar to a shelterwood treatment in a timber production system, in which trees are thinned just enough so that regeneration of the tree understory is encouraged while residual trees provide shelter.  In a silvopastoral system, thinning allows light in for forage growth for livestock.  Trees can be managed for sawtimber with proper spacing of trees.  Non-timber forest products such as nuts and fruit may be harvested as well.  I have seen pasture on a northern Florida cattle ranch in which oak trees provided acorns for wild pigs, thus bringing in extra income from hunters for the ranching outfit.

Row plantings,when it comes to handling livestock, have a great advantage over evenly-distributed grids of trees. Livestock perceive lines of trees as a solid fence which they will move along with a minimum of herders needed to do the job. All livestock have a point of balance at the shoulder, and will move ahead as long as the herder remains behind this point. In a pasture evenly distributed with trees, the livestock do not perceive a fence, and they will tend to spread out. Trees will then block the line of sight to the herders.  At this point the livestock will no longer see the herder behind their point of balance and will tend to bog down and become difficult to herd. In such a pasture, more time and personnel are required to move a herd than in a pasture with trees planted in rows.
Row plantings provide the most edge for species such as deer and upland birds that need both the shelter and the open space provided by the ecotone between woodland and pasture.  In addition, row plantings of trees grown for timber or pulp are easiest to harvest.

Living snow fences, when properly designed, will harvest snow and distribute it over a field.  Deep drifts are avoided, and water from snowmelt is better distributed over the pasture for forage growth.  Snow fences can divert snow away from a road, making access easier for vehicles used for timber harvesting or livestock operations.  Snow fences can also provide the same microclimate moderation benefits as windbreaks.

Outdoor living barns provide shelter on winter feedgrounds and calving grounds in severe weather events that are common in winter and spring.  Such shelter can greatly cut livestock losses by reducing wind, raising temperatures, and reducing snow depth within the shelter at the time of year when livestock are most vulnerable.  The placement of outdoor living barns is critical.  Livestock will drift with a storm, so the shelter should be located at the end of the pasture that is farthest away from the direction from which the prevailing winds blow. Livestock must have easy access through an opening that faces away from the wind direction.

Small groupings of trees provide a place in open pastures for livestock to shade up in hot weather.

Windbreaks shelter buildings and working corrals, and protect livestock and pastures from the drying and chilling effects of wind.
 
 
 

Silvopasture links:

 Live Fences - http://ppathw3.cals.cornell.edu/mba_project/livefence.html
This site provides information about hedges and living fence posts.

 USDA National Agroforestry homepage - http://www.unl.edu/nac/index.html
This link leads to the online NAC brochures on silvopasture and other topics in agroforestry.

 Silvopasture, an agroforestry practice - http://www.agroforester.com/overstory/overstory36.html
One of many good articles to be found in The Overstory, a free e-mail agroforestry journal.

 Silvopasture, a new land use option - http://www.irishscientist.com/P57a.htm
Silvopasture in Northern Ireland.

 PFRA Shelterbelt Center Publications - http://www.agr.ca/pfra/shbpub/shpub.htm
Articles from Agriculture and Agrifood Canada.

 A.R.T. Silvopasture - http://www.agroforestry.co.uk/silvop.html
The Agroforestry Research Trust is an English not-for-profit charity which researches temperate agroforestry.

 Journey to Forever - http://journeytoforever.org/index.html
"Mixed farming is best. Nature never tries to raise crops without animals, and the more species in attendance the better... it means increased biodiversity... fewer pests, less disease, higher yields, fertile soil, a healthy farm, and all your eggs in many different baskets."  This quote comes from an excellent Asia-based NGO website, which offers information on trees, soil and water, sustainable farming and technology, silvopasture, and agroforestry, and has a very useful section on using the internet.

 Indian agroforestry - http://www.daviesand.com/Papers/Tree_Crops/Indian_Agroforestry/index.html
Agroforestry as practiced by pre-European Native Americans in the Northeast U.S.

 Livestock behavior - http://www.grandin.com/
A most interesting site by Dr. Temple Grandin has information about livestock behavior and facilities design that may be useful in planning the spatial pattern of trees in a livestock pasture. It also includes information about humane treatment of livestock, and animal rights.

 National Range and Pasture Handbook - http://www.ftw.nrcs.usda.gov/glti/NRPH.html
This handbook from the Grazing Lands Technology Institute of the USDA includes a chapter on the many ways to diversify a grazing enterprise, including silvopasture.

Technique for maggot production - http://www.ias.unu.edu/proceedings/icibs/ibs/songhai/index.htm
Maggots as a food source for fish and fowl are being raised at the Songhai Centre in Porto-Novo, Benin.  They recommend maggotries be located among trees to keep the temperature down and to decrease odors.

Pastoralism in semi-arid West Africa - http://www.icraf.cgiar.org/regional/region_3/region_3.htm
The traditional silvopastoral system of the semi-arid West African lowlands is breaking down under the demand for firewood.  Go to this page to see ICRAF's work in this region.

Cornell courses - silvopasture - http://www.instruct1.cit.cornell.edu/courses/hortdl/agroforest/systems/IIIB5AFSYSTEMSLeft.html

Arid silvopasture in India - http://www.vedamsbooks.com/no19062.htm
Vedams Academic Books from India offers Silvopasture Management in Hot Arid and Semi Arid Ecosystems by N.K. Sharma, R.P. Singh, and Manjit Singh on this page. It examines the benefits of silvopasture on degraded lands, with case studies.
 
 
 

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This page was created by Virginia Harrison, a Peace Corps Masters International Student in Forestry at Michigan Technological University. vgharris@mtu.edu