8.  SOME AGROFORESTRY PRACTICES IN KENYA                   

8.3  Trees on boundaries

Spatial arrangement

Tree growing on farm boundaries is a very common practice, but it requires agreement between the neighbours involved to avoid conflicts. There are different ways of sharing trees planted on a boundary. Sometimes two rows of trees are planted, one on each side of the boundary, and then each farmer grows and manages his own trees. A disadvantage with this system is that it occupies more land than a single row. If trees are grown in a single row, the neighbours can agree on ownership of every second tree, for example. In such cases it is recommended that trees of the same species are grown, although it may be difficult to keep track of which tree belongs to which farmer. If different species are chosen, one species may outcompete the other and one of the two farmers be disadvantaged. Another option is for the neighbours to agree to own trees in different sections of the boundary. This may be easier than owning every second tree, and it is then possible to choose different species for different sections according to the farmers' preferences.

Figure 8.2 A line of trees along a boundary

Areas where the practice is relevant

This technology is relevant for all farming areas except irrigation schemes.

Establishment and spacing

Initially trees can be established at a close spacing (0.75-1.00 m) and then later thinned for poles, fito or firewood to a final spacing of 1.5-3.0 m. With double rows the spacing between the rows should not be less than 2 m. The tree propagation method will depend on the species, but use of seedlings or transplantation of wildings are common.

Management aspects

Management is similar to that for trees in fields.

Benefits

In small-scale farming areas boundary planting is usually enough to reduce wind speed, and there is no need to establish windbreaks. Trees on boundaries which are regularly pollarded can meet most of a family's need for firewood. In addition, other products and services are obtained and the boundary is effectively demarcated.

If the trees are not well managed there may be negative effects on crops, and if competitive species are planted root competition may be a problem. Conflicts with neighbours may arise if the sharing arrangements are not well handled.

Examples of species

Certain species, e.g. Cordia abyssinica and Croton megalocarpus, have traditionally been used as boundary markers. Grevillea is a very popular tree too. Trees with a short lifespan, e.g. Sesbania spp. and Acrocarpus fraxinifolius, are less suitable unless they are combined with more permanent trees. Competitive trees such as eucalypts, pines and Acacia mearnsii should be avoided. Many other non-competitive trees are suitable (see the list under "Trees in fields"). Non-commercial fruit trees, e.g. Syzygium cuminii, Vitex spp. and Annona spp., can also be suggested.