TREES IN ALLEY CROPPING - COMPETITORS OR SOIL IMPROVERS

Agroforestry has a high potential to sustain agricultural production i n the humid tropics. One specific type of agroforestry, alley cropping , has received much attention as a means of producing staple food crop s within an agroforestry system. There is now substantial evidence tha t alley cropping maintains soil fertility above levels found in pure a nnual cropping systems. Nevertheless, competition between the trees an d crops can significantly reduce yields by the crop. A model is presen ted of how the balance between the improved soil fertility in alley cr opping and competition from the trees determines the final crop perfor mance. Better understanding of the factors that determine crop yield w ill enable improved design and management of alley cropping systems, a nd may allow alley cropping to become a more reliable means of improvi ng crop production.