Tropical Agroforestry: Integrated Systems for Diverse Products and Needs

Kim Wilkinson

Agroforestry is about more than simply planting trees. The key is to maximize the number of beneficial connections formed between trees and other elements on the farm. Some agroforestry systems are very simple, forming just a few connections. Other agroforestry systems are more complex, and their form and function can ultimately resemble a multi-storied forest, with an intricate web of connections. In all of its forms, agroforestry is about using trees to recreate some of the beneficial connections and natural processes that support sustainable productivity.

Some of the benefits of agroforestry include: 1) Greater long-term economic stability through diversified product; 2) Increased total yields per acre; 3) Reduced need for purchasing off-farm inputs (fertilizers, insecticides, fuels); 4) More efficient use of land to provide for human needs, allowing more land to be left to nature; 5) Protection from wind and erosion.

Some examples of tropical agroforestry systems follow.

Silvopasture: World demand for timber is steadily increasing, while availability of hardwoods from tropical forests is decreasing. Some of the future timber supply will come from large plantations. However, timber and wood products can also be a sustainable, high-value yield from farms and agroforests. Silvopasture systems integrate livestock, forage pasture and trees. In this system, the livestock keep down the grass, reducing or eliminating the need to mow, slash, or use herbicide. Their manure contributes fertility to the trees, reducing the need to apply fertilizer. And, the livestock produce a steady economic income. The trees in this system provide shade for the livestock, which is important in the tropics where heat affects the productivity of livestock. The shade may also benefit the forage component. Also, the trees provide a diversified and long-term economic product.

Orchard Alley Cropping: Orchard alley cropping systems integrate orchard crops with nitrogen-fixing trees. Nitrogen-fixing plants provide the major source of fertility in natural ecosystems, and this natural source is reestablished in the farm by planting rows of nitrogen-fixing trees in the orchard. The orchard crops are grown in the middle of the "alleys" formed by the nitrogen-fixing trees. The nitrogen-fixing trees are cut back and applied as nutrient-rich mulch to the orchard crops. The mulch also conserves moisture, suppresses weeds, and encourages beneficial soil microorganisms. Alley cropping systems have been tested with annual crops for several decades. Western SARE funded the first project to study alley cropping with orchard crops. The results of that two-year study were very promising. The hedgerows provided the equivalent of over 500 lbs. of chemical fertilizer annually. In only two years time, the soil showed significant increase in total nitrogen, with improvements in other nutrients and pH as well. Crops showed faster growth. A financial analysis showed that the cost (including hedgerow installation and labor to prune and mulch) was about what we would have paid for organic amendments and mulch over the same period of time. The financial benefits of this practice increase for more remote farming areas (such as the outer islands of Hawaii or other Pacific Islands), where the costs of transporting and importing fertilizer are even higher.

Mixed Coffee Agroforests: Coffee agroforests such as those found in Central America include coffee trees, nitrogen-fixing trees, and long-term timber trees. In this system, the nitrogen-fixing trees provide mulch and fertility to the coffee crops, as well as a managed shade system. The timber component provides diversified products and can make the total yield of the system over time higher than if coffee were grown alone. Also, some ecologists have determined that these systems provide excellent wildlife habitat for birds and other wildlife, which contributes to the pest/predator balance and can also help with market positioning for eco-friendly products.

The above systems have in common that they are more diverse than monocultures, and beneficial connections between the diverse elements are encouraged. Human inputs can be reduced as natural functions such as the cycling of organic matter, the grazing of livestock, or the balance of pests and predators come into play to support productivity.

Agroforestry is an integrated approach to farm systems. It involves learning to work with and take advantage of natural processes that support productivity. This approach can help reduce inputs from off-farm, contribute to ecological balance, and provide diversified economic products. The protection and planting of agroforestry trees can serve as an important, locally achievable, and cost-effective step in promoting sustainable development and healthy rural enterprises

Kim Wilkinson
AgroForester
PO Box 428
Holualoa, HI 96725
Tel: (808) 324-4427
kim@agroforester.com
http://www.agroforester.com

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