The characteristics of agroforestry
Agroforestry is an activity that combines production on the same plot of land, from annual agricultural activities (such as crops and pasture) and from delayed long-term production by trees (for example timber and services). This is obtained either by planting trees on agricultural land or by cropping (for example after thinning) on forested land. Plots that combine arable intercrops with forestry trees are silvoarable plots, while wooded plots with pasture under the tree canopy are known as silvopastoral plots.
Wheat and walnut agroforestry plot
(Restinclières – France)
The advantages of agroforestry
Agroforestry provides a different land use option, compared with traditional arable and forestry systems. It makes use of the complementarity between trees and crops, so that the available resources can be more effectively exploited. It is a practice that respects the environment and has an obvious landscape benefit. Efficient, modern versions of agroforestry have been developed, that are adapted to the constraints imposed by mechanisation. The agroforestry plot remains productive for the farmer and generates continuous revenue, which is not the case when arable land is exclusively reforested. Agroforestry allows for the diversification of farm activity and makes better use of environmental resources. Agroforestry has interesting advantages from three different perspectives.
From the arable perspective
- Diversification of the activities of arable farmers, with the building-up of an inheritance of valuable trees, without disrupting the revenue from those plots which have been planted.
- Protection of intercrops and animals by the trees, which have a windbreak effect, providing shelter from the sun, from the rain, from the wind, holding the soil in place, and stimulating soil microfauna and microflora
- Recovery of some of the leached or drained nutrients by the deep roots of the trees; enrichment of the soil organic matter by tree litter and by the dead roots of the trees.
- Possibility of combining the interest of the owner (for an inheritance of wood) and the farm (for access to cultivated land). Possible remuneration for the arable farmer for looking after the trees
- An alternative to full reforestation of arable land, permitting the continuation of arable activity on land whose arable potential is therefore conserved. The tree component can be reversed, the plot stays “clean” (free from scrub) and is easy to destump when the trees are clear felled (the stumps are in lines and few in number).
- In silvopastoral plots, fodder units can be available at different dates compared to full cropped plots, extending the grazing calender.
Wheat sowing in a poplar agroforestry plot (Vézenobres – France)
From the forestry perspective
- Acceleration of the diameter growth of the trees by wide spacing (+80% over 6 years in the majority of the experimental plantations). Reduction of the capital cost of the plantation, by reducing the number of trees planted with no commercial future. A large reduction in the maintenance costs of the plantation, due to the presence of the intercrops.
- Improvement in the quality of wood produced (wide regular rings, suited to the needs of industry), because the trees are not subjected to cycles of competition and thinning.
- Guaranteed follow-up and tree care due to the arable intercropping activity. In particular, protection against the risk of fire in susceptible areas, with pastoralism or with intercrops like vine or winter cereals (clear bare ground in summer after stubble ploughing).
- Agroforestry plantations on arable land allow the development of a quality wood resource that complements, rather then competes with, the products from traditionally exploited forests. It is especially important to produce wood that can substitute for tropical sawlogs, which will soon decline in availability and quality. The areas concerned will remain small in terms of their absolute value, but the production of wood from them could become a critical input to the European wood supply network. Tree species that are little used in forestry, but are of high value, could be grown in agroforestry systems: service trees, pear trees, common sorbs, walnut trees, wild cherry trees, maple trees, tulip trees, paulownias, etc…
From the environmental perspective
- Improvement to the development of natural resources: the total wood and arable production from an agroforestry plot is greater than the separate production obtained by an arable-forest separate cropping pattern on the same area of land. This effect results from the stimulation of complementarity between trees and crops on agroforestry plots. Thus, weeds, which are spontaneously present in young forestry plantations are replaced by harvested crops or pasture; maintenance is less costly and environmental resources are better used.
- Better control of cultivated areas of land: by substituting for arable plots, the agroforestry plots contributes to diminishing the cultivated area of land. The intensification of environmental resource use by agroforestry systems is not resulting in more crop products.
- Creation of original landscapes that are attractive, open and favour recreational activities. Agroforestry plots have a truly innovative landscaping potential, and would improve the public image of farmers to society. This will be particularly the case in very sparsely wooded areas, where plots are developed by planting arable land, and in very heavily wooded areas, where plots are developed by thinning the existing forest.
- Counteract the greenhouse effect: constitution of an effective system for carbon sequestration, by combining the maintenance of the stock of organic material in the soil (the case especially with meadows), and the superimposition of a net fixing wooded layer.
- Protection of soil and water, in particular in sensitive areas.
- Improvement of biodiversity, especially by the abundance of “edge effects”. This in particular, permits a synergistic improvement, by favoring the habitat of game. The integrated protection of crops by their association with trees, chosen to stimulate the hyperparasite (parasites of parasites) population of crops, is a promising way forwards.
- These favorable characteristics are as coherent with the many objectives of the laws guiding agriculture and forestry, as they are with the directing principles of the Common Agricultural Policy.
Young walnut trees in lavanda plot