6. THE CROP COMPONENT

6.1 Factors of importance for interaction with trees

Some factors of importance in the relationship between crops and trees have already been touched upon in the previous chapter. Some of the more important are:

• Light demand

• Demand for moisture and nutrients (or the "aggressiveness" of the crop)

• Potential for bird damage

• The distribution of roots in the soil profile

• The potential for wind damage.

So far no systematic review of various crops has been made with regard to such factors. Most attention has been paid to the trees since they have often been regarded as the "new" component. The crop component in the system has been taken for granted and it is assumed that it is the tree component that has to be adjusted to fit into the farming system.

In order to properly understand the potential for integration of trees in a farming system, however, it is important to know the characteristics of the different kinds of crops as well as of the tree species that might be combined with them.

In the following section some important crops will be described, as far as possible with special reference to the factors mentioned above. The selection of crops to be covered posed a problem in terms of their definition as trees or shrubs. The crops covered are crops in a rather narrow sense; thus, for example, fruit trees have been excluded. Coffee, tea and cassava have been included in spite of being woody shrubs, and so have bananas in spite of being tree-like herbs.