The advantages of Agroforestry Systems

In Brazil, several government policies aim to encourage socio-economic development actions linked to issues of environmental protection and sustainability. Within this context, the adoption of agroforestry systems (SAFs) is justified by the need to associate agricultural production with environmental services, such as carbon sequestration, increased water stock and quality, soil conservation, reduced erosion, and increased biodiversity of production systems.

Due to their multiple use nature, agroforestry systems, in their different forms, constitute viable economic, ecological and social alternatives for strengthening agriculture. Consequently, they promote a series of benefits such as increases in production, employment levels and income for rural producers, always focusing on sustainable development, that is, production that respects the environment.

In SAFs, trees and shrubs are cultivated in an interactive way with agricultural crops, pastures and/or animals, aiming for multiple purposes, constituting a viable option for better use of the soil, to reverse the degradation processes of natural resources, to increase the availability of wood, food and environmental services. These systems are classified according to the nature and arrangement of their components, and can be called: Silviagricultural, those made up of trees and/or shrubs with agricultural crops; Silvopastoralism, cultivation of trees and/or shrubs with pastures and animals; and Agroforestry, cultivation of trees and/or shrubs with agricultural crops, pastures and animals.

Forestry, based on species of the Eucalyptus genus, stimulated by tax incentives, made the forestry sector highly competitive, mainly in the planted forest segment. However, forestry activity still presents some restrictions for medium and small producers, mainly due to cash flow problems and long investment periods. However, this behavior has been changing through the possibility of using agroforestry systems, which allows the diversification of forestry and agricultural products in the same area unit, and the generation of income and jobs.

Traditional eucalyptus plantations are represented by dense forest masses, planted at regular spacing and normally with a single species. However, on rural properties, in addition to this possibility of planting, trees can also be planted in an integrated manner with agricultural and livestock activities or even as providers of services such as windbreaks, hedges, animal protection without, however, , disregarding its potential to generate economic products.

Planting trees in pasture and/or agricultural areas can result in several benefits for ecosystem components: climate, soil, microorganisms, plants and animals. In this way, the rural producer, in addition to guaranteeing more favorable environmental conditions for his pastures and livestock, also guarantees a supply of wood (for his own use or trade), without having to abandon his agricultural or livestock vocation.

In SAFs, trees also have the potential to improve soils through different processes. In summary, they can influence the quantity and availability of nutrients within the zone of operation of the root system of intercropped crops, mainly due to the possibility of recovering nutrients below the root system of agricultural crops and pastures and reducing losses due to leaching and erosion. Therefore, the cycling of mineral nutrients, in terms of sustainability, is greater in agroforestry systems.

In degraded pastures or those beginning to be degraded, soil cover is deficient, therefore more subject to the harmful effects of erosion, both water and wind. The presence of trees in silvopastoral systems produces important effects in terms of soil conservation and protection against erosion.

Research carried out on sandy soils in the Alegrete/RS region found that soil losses, in the period from July to September 2004 (42,9 mm of rain), were significantly greater in the area cultivated with oats and corn. These losses were in the order of 359 kg/ha compared to 42 kg/ha lost in the area with native pasture and only 18 kg/ha in the silvopastoral system, with eucalyptus. These results prove the fragility of these soils and show the importance of trees as essential elements in the process of protecting them.

In agroforestry systems, lower planting densities and different spatial arrangements of forest species in the field are normally used. More dense plantings result in the production of a high number of trees with small diameters, which are normally used for less noble purposes such as firewood, charcoal, cellulose, crates and stakes for fences. Wide spacing results in a smaller number of plants per unit area, making access for machines for planting and cultural treatments easier. They also facilitate the removal of wood and employ less labor, in addition to allowing the production of wood with better commercial value (posts, beams, supports and sawmills). Disadvantages include a greater need for cultural treatments and less natural pruning.

In the production of high-quality wood for sawmills, the spaces between plants must be larger than normal. Management practices in eucalyptus, characterized by wide initial spacing, early and heavy thinning and high pruning, prove to be superior to traditional ones, with the production of good quality wood, with good economic results. Furthermore, it allows the penetration of high levels of radiation into the understory which, in turn, favors the satisfactory development of other species, enabling the integration of agricultural, forestry and livestock activities in a mixed production system.

Within this context, one of the most important decisions in establishing silvopastoral systems, for example, is the definition of tree spacing and arrangements. This decision will determine the condition of the light environment for forage growth from planting to harvesting the trees. The greater the spacing between the tree lines (rows), the greater the radiation penetration into the forage substrate, favoring the accumulation of biomass. However, the spacing between the rows cannot be excessive to the point of compromising the quantity and quality of the forest product per area and the tree cover desired to protect animals and pasture.

Jorge Ribaski

Forest Engineer, PhD in Forest Sciences from the Federal University of Paraná and Researcher at Embrapa Florestas.E-mail: