The utilization of mycorrhizal fungi in agroforestry systems in the semiarid regions of Kenya.
Ishii T.
Author Affiliation: Laboratory of Pomology, Faculty of Agriculture, Kyoto Prefectural University, Kyoto 606-8522, Japan.
Scientific Reports of the Kyoto Prefectural University, Human Environment and Agriculture : 21-37
Abstract : About 80% of Kenyan land is arid and semiarid, and the introduction of tree-planting techniques is needed for improving the land. Soil productivity in Kenya has been attributed to a low content of vesicular arbuscular mycorrhizas (VAM), minerals (especially N and P). When soil samples were collected from 103 orchards at 25 locations representing 13 soil types and 4 regions, the number of VAM spores in 25 g of soil was 200 or less; in >60% of these orchards the number of spores was 50/25 g of soil. The paper reports a pilot project at Kitui, investigating the utilization of mycorrhizal fungi in agroforestry systems, and supported by JICA. Data are reported on the types of VAM spores collected (Glomus spp. were most common), the variation intensity of VAM infection with plant type (a high percentage of VAM infection was observed in several weeds) and in some tropical fruit trees (Carica papaya, Mangifera indica, Psidium guajava, Tamarindus indica and 2 indigenous species - Pachystigma schumannianum and Sclerocarya birrea). Various other tree species (shown in a table) also formed VAM. When papaya seedlings inoculated with Glomus caledonium were transplanted to a pilot field, inoculated plants showed both improved resistance to water stress and higher survival percentages than non-inoculated plants. A millet-cultivated soil medium was very effective as a VAM inoculum, although stimulation of VAM formation in the roots of Cassia (Senna) siamea, Melia volkensii, Terminalia prunioides, Vitex doniana and Ziziphus mauritiana was observed without VAM inoculation. Furthermore, the growth of nursery trees was increased by the soil medium, in particular, there was increased VAM colonization in the roots of Acacia aulacocarpa, Carica papaya, Cordia ovalis, Mangifera indica, Persea americana, Psidium guajava and Schinus molle, which was reflected in vigorous tree growth. The inoculation of VAM fungi and the application of charcoal will be also very useful for the production of nursery trees. These results suggest that the use of VAM fungi can make a useful contribution to agroforestry systems in the semiarid regions of Kenya.