A simple tree-crop interaction equation is re-interpreted in terms of resource capture. Benefits in physical yields from agroforestry are to be expected only when there is complementarity of resource capture by trees and crops. Most of the current biophysical hypotheses formulated for agroforestry research are based on this central tenet, specified for various resources, soil and climatic conditions.
Tag: biological competition
Agroforestry technologies for social forestry: tree-crop interactions and forestry farmer conflicts
The biological conditions are specified under which a tree-crop system can give a yield benefit. Models can be used to explore the wide range of options as regards choice of trees and crops, plant density, plant spacing and soil management. Although ample opportunities exist for tree-crop combinations to out yield monocultures of either trees or crops, the conditions under which both the tree and the crop combinations to outyield monocultures of either trees or crops, the conditions under which both the tree and the crop component as much benefit from the mixing are narrow. If in ‘social forestry’ systems the stakeholders (forestry organization and farmers) are exclusively interested in the tree and crop component, respectively, little harmony in management decisions can be expected and strict enforcement of rules is needed, but may not be feasible. If other types of sharing arrangement can be agreed on, a much wider range of locally adapted solutions can be found, which more fully exploit the opportunities of tree crop synergy.
A framework for quantifying the various effects of tree – crop interractions
Early assessments of the potential benefits of agroforestry at the farm level were based largely on the assumption that it is possible to extrapolate from existing information on forestry and agriculture (Huxley, 1983; Nair, 1993), and partly on observations of trad-itional agroforestry systems that showed increased growth of understorey vegetation (Ong and Leakey 1999; Kho et al., 2001). Various negative effects have also been rec-ognized, such as competition for moisture, excessive shading and allelopathy, although these have attracted much less attention from scientists. Most of the evidence of benefits and drawbacks of agroforestry continues to be qualitative or indirect, i.e. extrapolated from a wide range of systems, creating often un-realistic expectations of the benefits of agro-forestry technologies (Garcia-Barrios and Ong, 2004).