Acacias in 'remedial' agroforestry

The urgent need for large-scale reforestation programmes to reverse the environmental degradation in tropical areas is becoming increasingly obvious. However, the lack of a selection of fast-growing, multi-purpose trees for differing eco-systems, soil types and cropping systems has been a major constraint on both reforestation and agroforestry programmes in the past. Showing great promise is a little-known species of acacia, which can be used in hedge-row-intercropping and in a variety of soil improvement and wind damage limitation measures. Acacia baileyana, or Coo-tamandra wattle as it is known in its native Australia, has many beneficial properties. It is fast growing yet has hard wood; it resprouts after cutting; its leaves are good for fodder and its flowers attract bees. Being leguminous, it improves soil fertility. Its roots not only break up hard clay soils, thus increasing aeration and drainage but, as a result, make essential nutrients more easily available. When interplanted among citrus trees, the acacias also act as a windbreak, reducing wind damage. Coupled with soil improvement, this substantially increases citrus yields. Another little-known acacia found in Costa Rica, A. angustissima, has similar growth habits and properties. Although neither species grows into large trees, they are extremely valuable for use in hedgerow-intercropping systems. They can also be used as pioneer species for rejuvenating degraded land or as a nurse crop for other tree species. A better-known acacia, A.mangium was introduced in Panama not only to help rejuvenate nutrient-poor soils, but also to halt the spread of Imperata cylindrica, a tenacious and noxious weedy grass. Because of its quick growth, A.mangium was able to shade out the weedy grass. As in the two other species, A.mangium increases yields when used in a hedgerow-intercropping system, but its taller height and hard wood mean that it can provide construction timber. ICRAF PO Box 30677 Narobi KENYAThe urgent need for large-scale reforestation programmes to reverse the environmental degradation in tropical areas is becoming increasingly obvious. However, the lack of a selection of fast-growing, multi-purpose trees for differing eco-systems,..