Using trees to fertilize soil
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CTA. 1987. Using trees to fertilize soil. Spore 12. CTA, Wageningen, The Netherlands.
Permanent link to this item: http://hdl.handle.net/10568/44739
Trees can also be an important source of fertilizer that does not require spending hard-earned cash once they are planted. Furthermore, they have many other positive effects on the farm environment, including reducing soil erosion, acting as...
Trees can also be an important source of fertilizer that does not require spending hard-earned cash once they are planted. Furthermore, they have many other positive effects on the farm environment, including reducing soil erosion, acting as windbreaks and shading crops as well as providing sources of forage, food and pharmaceutical products. Above all, trees are also relied on for producing valuable sources of fuelwood, mainly in the form of twigs and branches, and even lumber when they mature and can be replaced by other trees. It is the nitrogen fixing ability of leguminous trees that makes them of special value for improving soil fertility. This is especially the case for trees such as Acacia, Albizia and Prosopis which were the subject of two seminars discussed in Spore No. 7 ('Nitrogen-fixing trees and soil biology') and Leucaena leucocephala which was featured in Spore No. 8 ('Leucaena's promising future'). Several genera of Papilioncae have also been found to be capable of forming rhizobia nodules, including Dalbergia, Erythrina and Sesbania, which is discussed in the accompanying article in this issue. Litter falling from such trees enriches the soil with large quantities of nitrogen and minerals absorbed by the trees, often from considerable depths. Studies carried out in Hawaii showed that leucaena leaves collected from one hectare contained 44 kg of phosphorus and 187 kg of potassium, as well as calcium and numerous trace elements. An added bonus is the increased organic matter content of the soil that, unlike chemical fertilizers, represents a much more lasting contribution to future crop production. For further details, see 'Potentials of forage legumes in farming systems of sub-Saharan Africa', reviewed in Spore No. 11 (page 15) and available from: ILCA P.O. Box 5689 Addis Ababa Ethiopia