8.  SOME AGROFORESTRY PRACTICES IN KENYA                   

8.6  Improved fallows

Spatial arrangement

When land is fallowed due to the need to restore soil fertility after a period of cultivation, shrubs can be sown to speed up the process. These shrubs can fix nitrogen and add organic matter to the soil.

Figure 8.7 Fallow field with Sesbania sesban as a rotational woodlot

Areas where the practice is relevant

This practice is relevant in areas where land is regularly fallowed. However, fallowing is not common in Kenya now due to population pressure, although it does occur in western Kenya (mainly in the Lake Victoria basin) and in semi-arid areas. Improving fallows is relevant where farms are relatively large, and where labour is more of a constraint than size of farm holding. Improving fallows by establishment of shrubs is not a very common practice in Kenya.

Establishment and spacing

Since very many individual shrubs are required, all with a relatively short life span, a simple and cheap propagation method is necessary. Direct sowing is the best option. The denser the spacing the more effectively will weeds be suppressed.

Management aspects

The shrubs require little management once they are well established. But protection from livestock, is an absolute necessity. If the shrubs are very densely spaced some thinning can be done for harvesting of staking material, fito or firewood. When land is to be brought back under cultivation, some shrubs can be left to supply propagation material for the next fallow period.

Benefits

The main benefits are quick restoration of soil fertility and wood production. The risks or potential problems are damage by livestock and increased labour demand for establishment and up-rooting of shrubs.

Examples of species

Nitrogen-fixing shrubs which are easy to propagate and which have a short lifespan and relatively small root system are desirable. Sesbania spp. and Gliricidia sepium are promising.