Agro-Ecological Zones of the Tropics, with a Sample from Kenya

Ralph Jätzold, Horst Kutsch


The aim of reducing the fundamental danger of hunger in the Third World can be achieved through well-adapted agricultural development, and this step by step. One of these steps is the system of "Agro-Ecological-Zones (AEZ)" that determines on the base of natural factors agro-ecological zones as zones of accurately defined potential land use. The results of AEZ-calculations allow for locally differentiated agro-consulting at district level. If other relevant factors are included, it is possible to calculate farm models also. The F.A.D. zoning system (3) does not seem to be exact enough for such a large scale. Therefore a more detailed (differentiated) system had to be developed beginning with the so-called "main zones". These are determined by mean, minimum, and, if necessary, maximum temperatures and by the, yield probability according to crop water requirements of the most important crops and also for pasture and forage. The "sub·zones" are determined according to a 60% probability factor of the length of the growing period (in decades), which is important for the right choice of crop varieties.
This article tries to show how complex the land use potential of a district can be, using the example of the Embu-District which covers the humid region from Mt. Kenya until the arid Tana-Basin.

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