5. STAGES IN THE DEVELOPMENT OF A METHODOLOGY

5.2 Agroforestry land utilization types

It is evident that land suitability for agroforestry cannot be assessed without clear definitions of the kinds of land use

being referred to---in evaluation terminology, the land utilization

types. The first principle of land evaluation is that suitability can only be assessed with respect to specified kinds of use. In evaluation procedures, identification, refinement and description of land utilization types follows initial discussions, preceding determination of requirements (Figure 1, p. 5).

All forms of agroforestry possess one distinctive feature as land utilization types, namely that by definition they include at least two components, tree and non-tree. The former consists necessarily of multipurpose trees, again by definition; it may include agricultural tree crops, e.g. coffee, coconuts. The non-tree component may include agricultural crops, pasture species and livestock species.

At the most disaggregated level, it is possible to assess environmental requirements of individual species of tree, crop, pasture plants and livestock. These may be subdivided, trees into varieties (e.g. the varieties of Leucaena leucocephala), crops into cultivars and livestock into breeds. These may be referred to as components of agroforestry.

A second descriptive term is the agroforestry practice, consisting of components combined in some particular manner in space and time, e.g. a live fence, alley cropping, a planted tree fallow. Agroforestry practices alone are rarely a sufficient form of description for assessment of requirements. Some are more appropriate to certain environments, e.g. windbreaks to dry climates, whilst others appear to function better over a limited range of conditions, e.g. 'home gardens' are mainly found in wetter regions. For the most part, however, practices serve as a descriptive term for land utilization types described in more detail, and one means of classifying them.

Table 2. THE ICRAF ENVIRONMENTAL DATA BASE: EXAMPLE OF OUTPUT FROM THE REQUIREMENTS FILE.

At the most aggregated level there is the agroforestry system, described in detail with respect to its biological, technical, economic and social aspects. The Chagga home gardens on the slopes of Mount Kilimanjaro, Tanzania, are an example of such a system. As employed in the ICRAF agroforestry systems inventory, the term refers to existing systems, traditional or modern.

Agroforestry systems are frequently specific to the social and economic setting of a particular area. Consequently the precise environmental requirements are not always transferable to other areas. For example, land with many boulders can be cultivated where the accepted practice is hand hoeing, or where strong communal spirit or cheap labour availability permits their removal. However, the agroforestry system may well be appropriate as a land utilization type in evaluations for specific local areas.

For formulation of land use requirements on a broader scale, a more generalized form of land utilization type is needed. This would contain the technical elements in some detail, including plant species, but would give the social and economic conditions only in generalized terms as a setting. An example of such a description is:

Practice: alley cropping. Trees; Cassia siamea, Melia azedirach. Crops; maize, with field beans and/or cowpea in rotation; fallow infrequent. Livestock; work oxen only. Inputs: improved seed; fertilizers, manure and crop protection chemicals nil or low. Management; ox ploughing, hand weeding, hand harvest. Conservation; trees aligned along contour if land sloping. Social and economic setting; low capital and high labour intensities, smallholdings (generally 5 ha), low income levels (GDP< 500 per capita 1984).

The above degree of detail appears to be the appropriate form for specification of a land utilization type for systematic evaluation purposes. On the one hand it is sufficiently specific to make formulation of environmental requirements practicable; on the other, sufficiently generalized to make it available for consideration over a reasonably wide range of social and economic circumstances. More detail can be added as appropriate, e.g. tree-row spacing and pruning regime in the above example. The definition of a land utilization type permits the degree of detail to be varied as required by circumstances.