Agroforestry in Semi Arid Areas

Backgrounder

Kenya’s semi‑arid areas are under increasing ecological pressure due to growing population and a lack of arable land.  Grazing lands are threatened in places where the number of cattle, goats, and sheep is now more than twice the recommended maximum for the type of land. Rainfall is low, the land produces little, and there are shortages of fodder.

The Kenya Forestry Research Institute is developing agroforestry techniques to counteract the soil erosion and poor conditions.  Here are some of the ideas they are promoting.

Growing hedgerows of trees among crops can increase productivity and improve and protect the soil.  The most promising trees include species of Leucaena, Gliricidia, Cassia, and Sesbania which provide fodder, mulch, and fuelwood while preventing soil erosion and surface water runoff.

Wooden fences in the area are constantly attacked by termites and need to be replaced frequently, using scarce trees to provide the wood.  Live fences provide a solution to this problem.  Three species are recommended to farmers; ber (Ziziphus mauritania), Molina (Caesalpinia spinosa) and Jerusalem thorn (Parkinsonia aculeata).  The trees are planted less than 50 cm apart and are cut back at 30 to 50 centimetres above ground to stimulate the growth of side branches.

atural vegetation in the grazing lands is prevented from maturing by lack of moisture and constant browsing by animals.  A package of treatments has been devised for eroded grazing land, to protect both natural vegetation and newly planted trees and shrubs.  This includes: digging a 2‑metre‑long V‑shaped trench upslope of the tree to improve water retention; pruning the tree to one main branch to promote upward growth; surrounding the tree with thorny bushes to protect it from animals while the main branch is growing; constructing ditches for erosion control; introducing appropriate tree, shrub, and grass species to enrich the land.

Four species of fruit trees have been introduced to increase available food and income:  mango, pawpaw, rough lemon, and guava.

The researchers are also working with farmers to experiment with techniques such as:  pruning the roots of seedlings and the stems if necessary; digging larger planting holes to encourage rapid root development; and planting promptly at the beginning of the rainy season to take advantage of all available moisture.

Groups of farmers, mostly women, participated in the experiments and planted the most promising species on their farms.  School children and self‑help groups are taught the importance and the methods of rehabilitating grazing lands.  They are given seedlings to start tree nurseries.  Information is disseminated mainly through radio programs, newspaper articles, women’s groups, and schools.