Fertilizer tree

Fertilizer trees are used in agroforestry to improve the condition of soils used for farming. They capture nitrogen from the air and put it in the soil through their roots and falling leaves. They can also bring nutrients from deep in the soil up to the surface for crops with roots that cannot reach that depth. Fertilizer trees are further useful for preventing fertilizer erosion, soil degradation and related desertification, and improving water usage for crops. Sesbania, Gliricidia, Tephrosia, and Faidherbia albida are known as fertilizer trees. Tree Lucerne or Tagasaste (Cytisus proliferus) is a well known fertilizer tree, able to fix more than 587 kg of nitrogen per hectare per year. It can increase maize yields from 1 ton per hectare per year to more than 10 tons ha/year in areas with more than 850mm of rain per year or a perched water table. Tree Lucerne is also used to create and maintain terra preta.

Use in Africa

Use of a fertilizer tree (Faidherbia albida) in Malawi and Zambia has resulted in a doubling or even tripling of maize yields. As part of evergreen agriculture, use of fertilizer trees are proposed as a means to improve food security. Niger has more than 4.8 million hectares of predominantly Faidherbia agroforests, while Zambia has 300,000 hectares.

In Zambia and Malawi, where Faidherbia trees are most widely used, farmers plant the trees in a checkerboard pattern every 30 feet throughout the field.

Fertilizer trees are used to prevent the expansion of desert, and keep agriculture viable in arid lands in many African countries.

See also

• Agroforestry
• Ecoscaping