Alley cropping is an agroforestry technique that integrates trees with crops to provide fertilizer and mulch. With careful design, this technique can also provide erosion control, windbreak, and animal fodder. The systems approach enables the trees to work together with other elements to provide many more benefits than the elements could provide independently.
Research shows that hedgerow intercropping is most advantageous in areas where (a) the subsoils are fertile and the rainfall reliable, thus minimizing competition; (b) slopes are steep, so that erosion control is an added advantage; (c) land tenure is secure; and (d) labour is available at low cost.
Contour hedgerows are efficient in soil conservation even in severe storms when conventional collection traps are unable to cope with the deluge. Long-term studies on 14% slopes at Machakos, Kenya, show that contour hedgerows of cassia and leucaena conserve 82% of the runoff and prevent 98% of erosion losses when compared with sole crops during infrequent but highly erosive rainstorms.