Agroforestry in Guatemalan Agriculture

Agroforestry is used within Guatemalan mountain terrain to preserve soil structure and nutrition.

 

High in the mountains of Chiquimula, Guatemala, poverty dictates that the rural villagers cultivate the available land to feed their families. Knowing of no alternatives, the residents of Chancó, Corral de Piedra, and Salitrón clear the mountainous terrain of trees to produce corn and beans, the traditional crops. During the dry months these cleared lands are barren and stark. The wet season brings rain which batters the steep slopes and erodes the exposed soil into streams and rivers. Though the river valleys receive the benefits of this erosion, the families high in the mountains face a constant decrease in their land’s productivity.

Gliricidia Sepium

The producers in these mountain villages recognize the degradation of their land, but poverty, tradition, and lack of education deter changes. Seeking feasible alternatives, the Benson Institute agronomic workers in Chiquimula are encouraging a farming practice called "agroforestry" to alleviate the productivity loss.

An agroforestry system combines trees and agriculture to improve soil quality and offer economic benefits. The system being employed in Guatemala, alley-cropping, requires that trees be planted in rows against the slope of land. Between each row is adequate spacing for the cultivation of a temporary crop. With proper management, the rows of trees will prevent soil erosion, add nutrients and organic matter to the soil, and provide firewood and lumber to reduce the cutting of existing trees.

Servin Flores, a university student meeting graduation requirements with the Benson Institute’s help, implemented agroforestry systems in Corral de Piedra as part of his community service requirements. Flores is an agronomy student at CUNORI, a satellite campus of the University of San Carlos, in his final year of studies.

In his association with the Ezra Taft Benson Agriculture and Food Institute, Flores worked with rural farmers who own land in Corral de Piedra. Property owners instead of renters are normally involved in the project because tenants have little desire to improve land they do not own. Conversely, property owners accept simple ways to increase land productivity. The two primary farmers who implemented Flores’ agroforestry system program are Héctor Villagrán and Pedro Acevedo.

The first step in establishing an agroforestry system is the nursery production of trees suitable for the system. According to Flores, the ideal tree for agroforestry systems is leguminous, has abundant and easily decomposable leaves, has a continuous strong growth habit, develops a deep root system, provides a useful wood, grows vertically, gives dispersed shade, and does not cause negative allelopathy.

Leguminous plants have the ability to take nitrogen from its unusable state in the atmosphere and convert it to nitrogen forms that can be used in the plant structure. Proper use of legumes can result in less need to apply nitrogen fertilizers to a soil and are thus a cost-effective input to a farming system. In leguminous trees most of the converted nitrogen is taken up by the plant itself and is thus not available to adjacent crops. But dropped leaves contain nitrogen that becomes available to other plants upon decay, without the cost of fertilizer inputs. Therefore, leguminous trees with leaves that decompose easily are central to agroforestry.

The growth habit of a tree is another consideration. A deep root system will not interfere with planting space nor will it remove too much water and nutrients from the upper horizons of the soil, the reserve for crops with shallow roots. Vertical growth reduces the shade that interferes with crop photosynthesis, as does a canopy which gives only dispersed shade. The ability of continuous grow well is particularly important. For optimum crop space and minimum shading, trees are cut back during the growing season and must reestablish themselves once shade will not affect crop production.

Farmers use A-Frame levels to mark curves along which they will plant trees.

Some trees can result in direct economic benefits for the producer. A tree that provides high-quality wood that can be used for construction or woodworking will supply extra money for the family as the tree is replaced with a younger one. Wood that provides good cooking fuel is also beneficial. Instead of removing existing trees to gather firewood, thereby advancing deforestation, the owner of an agroforestry system has a ready supply of fuel in his fields.

Allelopathy is a plant’s release into the soil of compounds that impact the growth of other plants. Dr. François Pellissier of the University of Savoie, Chambéry, France, states that "recent findings have demonstrated that tree-crop interactions may have significant bearings on the total productivity of an agroforestry system. Therefore, it seems essential that the allelopathy compatibility of crops with trees should be checked before being introduced to an agroforestry system" (Pellissier).

Several trees possess many of the beneficial characteristics described above. Among them is Gliricidia sepium (commonly known as balo -madre de cacao-), which grows commonly in Guatemala. Gliricidia is a small-sized deciduous tree often grown ornamentally for its beautiful pink flowers. Its hard, resistant wood is considered precious by some, and it has many uses in construction and woodworking. Being a nitrogen fixer, it was originally planted with cacao plants for the fertility it affords (Tropical). Gliricidia wood is also a high-energy fuel and has a strong continuous growth habit (Pacific, Cherry). Flores chose to use this tree in his work, though other genera such as Leucaena and Calliandra also provide excellent agroforestry characteristics.

Once the appropriate tree is selected, the nursery is begun. Small plastic bags are filled with soil and planted with the selected seeds. The seedlings are given the correct light conditions, sufficient water, and are kept free of weeds until they reach a size appropriate for transplanting.

While the trees are growing in the nursery, land preparation begins. In these areas of Guatemala, the fields incorporated into an agroforestry system are usually on steep terrain. The best slope for an agroforestry system is one that faces south, as southern exposure receives the most direct sunlight. On a southern slope, the trees will be planted in an east-west direction, which minimizes the shade on the surrounding crop as the sun moves across the sky.

The first step in preparing the field is to use a simple A-frame level (which can be made with three straight tree branches, twine, and a rock; see photo) to delineate rows against the slope of the land. If one leg of the level is higher or lower than the other, the weighted twine will fall too far to the right or left of center on the crossbar, showing that the row being marked is not horizontally level. A row has been properly marked when a person can walk along the row and not move up or downhill. Wooden stakes are positioned along the row as it is delineated.

According to Flores, the distance between the rows "basically depends on the following: the tree species, the crop which will be established, the slope of the terrain, and the position of the land with respect to the sun." The field owned by Don Pedro faces directly south and thus the spacing used by Flores was 15 meters. Don Héctor’s property required 20 meter spacing between rows to accommodate a less direct exposure to the sun. "When the direction of the field with respect to the sun is not ideal," says Flores, "the distance between trees must be greater and you must use trees which project a diffuse shade such as balo (madre de cacao or yaje -Leucaena leucocephala)".

Traditionally, the residues from the previous year’s crop are gathered and burned. Thus the organic matter from the plant is lost. Plant matter, when left in the soil, decays into humus, a soil component that provides fertility and structure to soils. In order to preserve this valuable soil component the Benson Institute agronomy staff works with the community residents to find ways to allow the residues to contribute to soil quality. Agroforestry provides a way for these residues to be used advantageously without interfering with traditional planting.

Once the rows are designated, the residues which would normally be burned are positioned instead along the stakes in the row. Thus the residues do not interfere with manual planting of corn and beans, and they are allowed to decompose to offer better qualities to the soil and improve growth of the young trees that will be planted along the same rows.

Once the land is prepared, the transplanting begins. Saplings are planted in holes dug along the rows on the slope at an interval of one to two meters. The distance is based on the same factors determining spacing between rows.

Pedro Acevedo, one farmer using agroforestry, plants a tree in his field.

Managers of an agroforestry system follow basic agricultural principles. Pest control must be employed, especially as the residues from the previous crop can harbor diseases and insects that can be transferred to the current crop. Weed control will need to be used with caution, as certain herbicides can damage the trees in the first few years of development. Pruning to eliminate crop interference is essential, as is assuring that the trees grow erectly. Flores suggests that a terracing system can also be applied in these agroforestry systems, reducing the inclination of the land between rows of trees.

“They are proud of having implemented these systems and they want to continue establishing agroforestry systems.” - Servin Flores

With proper management, an agroforestry system can contribute significantly to the productivity of depleted land. The permanency of the trees will prevent erosion from steep slopes, the nitrogen contribution from fallen leaves offers fertilization, the organic matter provides higher fertility potential, the wood from the trees can provide cooking fuel or income from being sold as a construction material, and during the dry season shade will prevent excess evaporation of soil water reserves for the next year’s planting.

Agroforestry has been well accepted by the producers in Corral de Piedra. Flores states "We can feel good about having achieved the adoption of these systems, which are now starting to gain popularity in the community. I’ve spoken with Don Héctor, Don Pedro, and other producers and they are proud of having implemented these systems and want to continue establishing agroforestry systems, as well as stands of trees for firewood, live fences, and fruit trees." Flores also mentioned that other farmers in Corral de Piedra are experimenting with their own ideas to put their systems to best use.

By promoting agroforestry, Servin Flores and the Benson Institute help farmers alleviate land depletion, provide economic options, and introduce to the people of Corral de Piedra knowledge that will foster ingenuity and ideas for future solutions. Using available resources to solve problems is a key to sustainable improvements.

Works Cited

Pacific Islands Farm Manual. "Gliricidia sepium: Its Name Tells Its Story."

Avaliable: http://agrss.sherman.hawaii.edu/onfarm/tree/tree000e. html [13 Oct. 1999].

Pellissier, François. "Allelopathy Research at the University of Savoie." Feb. 1999.

Available: http://www.univ-savoie.fr/labos/ldea/homedea3.htm [4 Oct. 1999].

Tropical American Tree Farms. "Madero Negro."

Available: http://tropicaltrees.co.cr/htm/tropical_hardwoods/madero_negro.htm#Madero Negro [13 Oct. 1999].