What is Agro Forestry
Agroforestry is the management of trees for forest products. It can be an integral component of productive agriculture. It has application to multiple use agricultural land, or as a single land use. It may include existing native forests and forests established by landholders. It is a flexible concept, involving both small and large sized land holdings. These forests are multi functional, serving several purposes simultaneously.
Agroforestry has the potential to combine four elements of land management:
- Agriculture
- Land Protection
- Forestry
- Conservation
Agricultural Element
Shelter and Shade
Agroforestry provides protection for stock, crops and pasture as follows:
- Increased stock performance
Agroforests protect stock from summer heat and winter cold. This can improve weight gain, milk production and fertility (Race, 1993). Unsheltered stock uses energy handling the stresses of heat and cold and have less energy available for production.
- Increase crop and pasture yields
Production is lost near trees but is more than offset by the gain in production within the rest of the sheltered area (Race, 1993). This is associated with reduced influence of wind, therefore increased water retention and stability of moisture levels (see Diagram 1).
| Diagram 1. Production and Shelter |
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Source: Race,1993
Nutrient Recycling
Tree roots take up nutrients that have leached beyond the reach of pasture, returning them to the topsoil when leaves fall and decompose.
Forestry ELement
Agroforestry can produce high quality valuable timber when trees are effectively selected and managed. Other tree products, such as fence posts, strainer posts, seeds, nuts and flowers can also be produced on the farm to increase economic diversity and income.
There are several forms of planned agroforestry and three of these are briefly discussed here.
Timber Belts
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| Timberbelt Planting |
Timber belts generally consist of 10 or less rows of closely spaced trees that provide shelter (windbreaks and stock shelter) and other commercial tree products. These plants can be managed to produce high quality knot free timber. Eucalypts, pines, cypress, acacias, poplars and grevilleas may be suitable (Cremer, 1990). Timber belts incorporate a slow growing supplementary species to provide low shelter and protect against the effects of winds. These species may also produce useful products. When the timber species is felled these supplementary species will have grown sufficiently to provide shelter by themselves. It is anticipated that the main benefit associated with this form is the protection it offers surrounding lands and stock.
Timberbelt planting
Wide Spaced
For ease of establishment and management wider spaced trees are planted in rows, often one species per paddock.
Horticultural cropping or silage production during the trees establishment years can be combined successfully in this wide spaced form of planting. Livestock can be introduced to a wide spaced agroforest when the trees have been established or when their protection can be provided. It is anticipated that agricultural production from wide spaced agroforests will decrease over time to a negligible level as the trees mature ready for harvest (Race,1993).
Wide Spaced planting
Cluster
Cluster planting is a circular design that combines timber production and shelter. It allows for economic fencing of trees during establishment years. It also allows for high density plantings of mixed species to be easily incorporated into current agricultural practices. When established it offers shade and shelter for livestock and saleable forestry products.
Land Protection Element
Salinity and Water Table Control
Salinity is mainly caused by rising water tables (McDonald, et.al.,1994). Trees help to lower water tables, acting as pumps to take up water from the soil and then evaporating it to the atmosphere (see Diagram 2.)
| Diagram 2. Trees and the Water Table. |
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Source: Race,1993
Soil Erosion Control
Soil erosion or loss results from the action of wind and water on unprotected soils. The forest canopy, roots and leaf litter all have a role in controlling soil erosion.
Water Logging
By water removal, established trees can substantially reduce water logging in their immediate area, which may result in improved land uses, e.g. pasture or crop.
Conservation Element
Indigenous Species
Use of trees of local genetic origin will maintain the biological structure of the local native flora and fauna. Also indigenous trees are often better adapted to local conditions than non indigenous trees and have higher productivity.
Wildlife Habitat
Trees support many forms of wildlife and increase biodiversity. Many of these species of wildlife (birds, insects) play a major role in controlling outbreaks of crop and pasture pests.