MYCORRHIZAL RELATIONS IN TREES FOR AGROFORESTRY AND LAND REHABILITATION

The mycorrhizal stimulation of trees by increasing the efficiency of n utrient uptake from soil is discussed with special reference to tree s pecies used in agroforestry/sylvopastoral systems. The occurrence of t he two major classes of mycorrhizas is indicated as are the soil, plan t and fungus factors affecting the size of the response. The low inten sity of rooting of many tree species and the prevalence of low fertili ty soils suggest large responses may be obtained frequently by inocula tion with mycorrhizal fungi selected for high efficiency or by managem ent to increase populations of indigenous fungi where these are highly effective but low in number. Effective mycorrhiza function may also a meliorate deleterious soil conditions other than nutrient deficiency a nd is important to maximize symbiotic nitrogen fixation. Inoculation o f tree species in the nursery is logistically feasible and inoculated arbuscular mycorrhizal trees, when outplanted, may serve as inoculum s ources for interrow crops. Future avenues of research are indicated.