General agro-forestry - silviculture and mixed farming solutions

Agro-forestry is an integrated approach to the production of trees and of non-tree crops or animals on the same piece of land. The crops can be grown together at the same time, in rotation, or in separate plots when materials from one are used to benefit another. Agro-forestry systems take advantage of trees for many uses: to hold the soil; to increase fertility through nitrogen fixation, or through bringing minerals from deep in the soil and depositing them by leaf-fall; and to provide shade, construction materials, foods and fuel. In agro-forestry systems, every part of the land is considered suitable for the cultivation of plants. Perennial, multiple purpose crops that are planted once but yield benefits over a long period of time are given priority. The design of agro-forestry systems prioritises the beneficial interactions between crops, for example trees can provide shade and reduce wind erosion. According to the World Agro-forestry Centre, “agro-forestry is uniquely suited to address both the need for improved food security and increased resources for energy, as well as the need to sustainably manage agricultural landscapes for the critical ecosystem services they provide” (http://www.worldagroforestrycentre.org/research/overview). Agro-forestry is already widely practiced on all continents. Using a 10 per cent tree cover as threshold, agro-forestry is most important in Central America, South America, and South East Asia, but also occupies a large amount of land area in Africa.

In addition to adaptation benefits, agro-forestry also has a function of carbon sequestration. Climate change mitigation functions of agro-forestry are described in the article 'Agro-forestry (mitigation)'.

Description

There are a broad range of classifications for Agro-forestry systems. These include: structural classification (composition, stratification and dimension of crops); to classification based on the dominance of components (such as agriculture, pasture, and trees); functional (productive, protective or multi-purpose); ecological; and socio-economic. Generally, however, agro-forestry systems can be categorised into three broad types:

• agrosilviculture (trees with crops),
• agrisilvipasture (trees with crops and livestocks) and
• silvopastoral (trees with pasture and livestock) systems.

Agro-forestry is appropriate for all land types and is especially important for hillside farming where agriculture may lead to rapid loss of soil. The most important trees for incorporating into an agro-forestry system are legumes because of their ability to fix nitrogen and make it available to other plants. Nitrogen improves the fertility and quality of the soil and can improve crop growth. Some of the most common uses of trees in agro-forestry systems are:

• Alley cropping: growing annual crops between rows of trees
• Boundary plantings/living fences: trees planted along boundaries or property lines to mark them well.
• Multi-strata: including home gardens and agroforests that combine multiple species and are particularly common in humid tropics such as in South East Asia
• Scattered farm trees: increasing a number of trees, shrubs or shaded perennial crops (such as coffee and cocoa) scattered among crops or pastures and along farm boundaries.

Any crop plant can be used in an agro-forestry system. When selecting crops, the following criteria should be prioritised:

• Potential for production
• Can be used for animal feed.
• Already produced in the region, preferably native to the zone
• Good nutritional content for human consumption
• Protect the soil
• A Lack of competition between the trees and crops

Table 1 shows five stages to the design and implementation of an agro-forestry system.

Agro-forestry can improve the resilience of agricultural production to current climate variability as well as long-term climate change through the use of trees for intensification, diversification and buffering of farming systems. Trees have an important role in reducing vulnerability, increasing resilience of farming systems and buffering agricultural production against climate-related risks. Trees are deep rooted and have large reserves, and are less susceptible than annual crops to inter-annual variability or short-lived extreme events like droughts or floods. Thus, tree-based systems have advantages for maintaining production during wetter and drier years. Second, trees improve soil quality and fertility by contributing to water retention and by reducing water stress during low rainfall years. Tree-based systems also have higher evapo-transpiration rates than row crops or pastures and can thus maintain aerated soil conditions by pumping excess water out of the soil profile more rapidly than other production systems if there is sufficient rainfall/soil moisture (Martin and Sherman, 1998).

Trees can reduce the impacts of weather extremes such as droughts or torrential rain. For example, a combination of Napier Grass and leguminous shrubs in contour hedgerows reduced erosion by up to 70 per cent on slopes above 10 per cent inclination without affecting maize yield in central Kenya (Mutegi et al, 2008). Research has also demonstrated that the tree components of agro-forestry systems stabilise the soil against landslides and raise infiltration rates (Ma et al, 2009). This limits surface flow during the rainy season and increases groundwater release during the dry season.

Agro-forestry can also play a vital role in improving food security through providing a means for diversifying production systems (Box 1).

Advantages of the technology

Agro-forestry has a broad application potential and provides a range of advantages, including:

• Agro-forestry systems make maximum use of the land and increase land-use efficiency.
• The productivity of the land can be enhanced as the trees provide forage, firewood and other organic materials that are recycled and used as natural fertilisers.
• Increased yields. For example, millet and sorghum may increase their yields by 50 to 100 per cent when planted directly under Acacia albida (FAO, 1991).
• Agro-forestry promotes year-round and long-term production.
• Employment creation – longer production periods require year-round use of labour.
• Protection and improvement of soils (especially when legumes are included) and of water sources.
• Livelihood diversification.
• Provides construction materials and cheaper and more accessible fuelwood
• Agro-forestry practices can reduce needs for purchased inputs such as fertilisers

Disadvantages of the technology

Agro-forestry systems require substantial management. Incorporating trees and crops into one system can create competition for space, light water and nutrients and can impede the mechanisation of agricultural production. Management is necessary to reduce the competition for resources and maximise the ecological and productive benefits. Yields of cultivated crops can also be smaller than in alternative production systems, however agro-forestry can reduce the risk of harvest failure.

Financial requirements and costs

In Eritrea, a large-scale five-year agro-forestry project led by the Ministry of Agriculture aimed at creating healthy and well-managed forest plantations to withstand the impacts of climate change was presented as part of the country’s NAPA strategy. The project had a total cost of just over US$$5 million, as detailed below:

A five-year project included in the NAPA of Senegal aimed at promoting agro-forestry had a total budget of US$ 258,000 for establishing community nurseries, plant growing, installation of plantations and rejuventation of regional forests (see Table 3).

Institutional and organisational requirements

To plan for the use of trees in agro-forestry systems, considerable knowledge of their properties is necessary. Desirable information includes the uses: the climatic adaptations of the species, including adaptations to various soils and stresses; the size and form of the canopy as well as the root system; and the suitability for various agro-forestry practices. The selection of crops also requires knowledge of uses, adaptation, and market opportunities (Martin and Sherman, 1998).

It is also important to understand how trees and crops interact. In simultaneous agro-forestry systems, trees and crops can share above-ground and below-ground space. Trees and crops interact in many ways, leading to both positive and negative effects on the growth of both trees and crops. These processes, which are very complex, are related to light, water, nutrients and wind.These processes also affect the soil itself. There are also indirect interactions, for instance related to pests and diseases. Cycling of soil organic matter, nutrients and water are processes that are central to understanding the interactions in agro-forestry systems.

Knowledge is also required about the main laws and decrees that influence the management of natural resources. It is important to understand the concept of tree and land tenure, including both the formal legal system and the traditional tenure systems and to be familiar with policies related to land use, soil and vegetation, and socioeconomics, including trade and market policies. An understanding of national, regional and local development plans and programmes relevant to agro-forestry and natural resource management is also required.

The institutional context is essential to natural resource management and agro-forestry. The main categories of institutions with a bearing on agro-forestry are shown in Table 4.

The policy and legal framework is of great importance for the sustainable management of natural resources. Local government and forestry authorities should be lobbied to simplify the legal processes for commercialisation of native wood and non-timber products grown in agro-forestry systems. Increased adoption of agro-forestry should be supported by government through finance. Research and training is required to match high value agro-forestry species with the right agro-ecological zones and agricultural practices (Neufeldt et al, 2009).

The implementation of the agro-forestry farming approach should be accompanied by the organisation of farmers into cooperatives in order to improve their capacity to negotiate better prices for their goods and avoid paying a percentage of their profits to intermediaries. Joining cooperatives gives farmers the status of organised producers, facilitating access to larger markets and organic and fair trade certification. As a result, farmers’ income can rise significantly. Farmers should also receive training on management issues, decision-making and participation in local administration, such as participatory budget and development planning at municipal level.

Barriers to implementation

Key barriers to the practice of agro-forestry are:

1. Poor access to agro-forestry inputs/resources including land tenure, tree tenure, water, seeds and germplasm, and credit.
2. Agro-forestry production or management issues relating to knowledge about agro-forestry systems, quality control, storage, processing of products, access to technical outreach services, and upfront costs versus long-term gain.
3. The main benefits of agro-forestry are perceived in the medium term at least five to ten years after establishment, this means that farmers must be prepared to invest in their establishment and management during several years before the main benefits are generated.
4. Marketing of agro-forestry products and services. Lack of access to transport, handling, processing, and marketing infrastructure, bans/restrictions on timber products, over-production, and lack of demand for products.

Opportunities for implementation

Agro-forestry provides an excellent opportunity to promote sustainable forest management while improving income-generating opportunities for local communities. Agro-forestry can provide a more diverse farm economy and stimulate the whole rural economy, leading to more stable farms and communities. Economic risks are reduced when systems produce multiple products. Likewise, this approach prioritises conservation and rehabilitation measures such as watershed rehabilitation and soil conservation.

References

• FAO (1991) Energy for sustainable rural development projects – Vol 1: A reader in Training Materials for agricultural Planning 23/1, Food and Agriculture Organisation, Rome
• Ma, X, JC. Xu, Y. Luo, S.P. Aggrawal SP, JT. Li (2009) “Response of hydrological processes to land-cover and climate changes in Kejie watershed, south-west China”. Hydrological Processes. Online. DOI: 10.1002/hyp.7233.
• Martin, F. W. and S. Sherman (1992). Agroforestry Principles. ECHO (Educational Concerns For Hunger Organization)
• Mithoefer, D. and H. Waibel (2003) Income and labour productivity of collection and use of indigenous fruit tree products in Zimbabwe. Agro-forestry Systems 59, 295–305.
• Mutegi, J. K., D. N. Mugendi, L. V. Verchot, J. B. Kung’u (2008) Combining napier grass with leguminous shrubs in contour hedgerows controls soil erosion without competing with crops. Agro-forestry Systems, DOI 10.1007/s10457-008-9152-3.
• Neufeldt, H., A. Wilkes, R. J. Zomer, J. Xu, E. Nang’ole, C. Munster, F. Place (2009) Trees on farms: Tackling the triple challenges of mitigation. World Agro-forestry Centre Policy Brief 07. World Agro-forestry Centre, Nairobi, Kenya.
• Raintree, J. B. (1986) An Introduction to Agro-forestry Diagnosis and Design, International Council for Research in Agro-forestry, Kenya
• UNFCCC (2008a) Nacional Adaptation Programmes of Action, Summary of Projects on Territorial Ecosystems identified in submitted NAPAs as of September 2008, United Nations