Agroforestry in Kenya

In their early agroforestry studies in Kenya , the water-balance BIDR team  showed that competition for water can be minimized by radically pruning the trees before planting the intercrop. Because of the reduced mass of tree foliage, the deeply rooted larger plants do not compete with the germinating crops for the runoff. Neither do they block the sunlight needed by the fast-growing shoots for photosynthesis. In addition, water in the upper layer of soil, which would otherwise be lost via direct evaporation, is utilized by the intercrop. The investigators found that when trees were pruned the overall productivity of the entire system was higher than that of the sum of the components when grown in separate fields. This results from the fact that the deeply stored runoff water (up to 6 m. beneath the surface) is preferentially utilized by the trees, while the planted crop takes its moisture from the upper layers of soil. 

[Droppelmann, KJ and PR Berliner, “Biometric relationships and growth of pruned and nonpruned Acacia saligna under runoff irrigation in Northern Kenya.” ForestEcology and Management 126:349-359 (2000); Droppelmann, KJ, JE Ephrath and PR Berliner. “Tree crop complementarity in a Runoff Agroforestry System.”Agroforestry Systems 50:1-16 (2000); Droppelmann, KJ, J Lehmann, JE Ephrath and PR Berliner, “Water use efficiency and uptake patterns in a Runoff Agroforestry System in an arid environment.” Agroforestry Systems 49:223-243 (2000)] 

These studies were carried out near Kakuma in dry northwestern Kenya (see Fig. 2). This area of high food insecurity is thinly populated by local Turkana residents, but contains tens of thousands of refugees from surrounding countries living in crowded camps. Because the area is largely the home of pastoralists, an agroforestry system was built around blue leaf wattle (Acacia salicina), a treelike leguminous shrub native to Australia, and sorghum.  Wattle can be used for grazing animals, such as sheep and goats, and sorghum grains can be included in animal feed or made into flour for human consumption. By increasing the usefulness of the fields, the needs of pastoralists can be supplied without exploiting large tracts of land. The investigators also found that runoff agroforestry is less affected by interannual rainfall variability than rain-fed systems and that it supports the natural regeneration of degraded rangeland. 

Fig.2. ​Intercropping in Kenya.

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