VESICULAR-ARBUSCULAR MYCORRHIZA EFFECTS ON GLIRICIDIA-SEPIUM AND SENNA-SIAMEA IN A FALLOWED ALLEY CROPPING SYSTEM

Nitrogen fixing and non-N-2 fixing legumes such as Gliricidia speium a nd Senna siamea have been used in alley cropping systems for soil impr ovement and source of N for food crops. However their establishments c ould be limited by P and moisture deficiencies in degraded soils. Vesi cular-arbuscular mycorrhizal fungi can help to overcome these deficien cies. We examined the effects of a vesicular-arbuscular mycorrhizal (V AM) fungus, Glomus deserticola, on the performance of sole hedgerow tr ees of Gliricidia sepium and Senna siamea and their mixtures (interpla nted) in a fallowed alley cropping experiment on a degraded Alfisol in southwestern Nigeria. Percentage root infection by VAM fungi was high er in inoculated plants than in uninoculated ones irrespective of whet her they were interplanted or non-interplanted. Inoculation with G. de serticola increased dry matter accumulation and nutrient uptake (N. P, Mg and K) but there was no significant interaction between mycorrhiza l inoculation and interplanting for growth and nutrient uptake except for the uptake of P, Mg and K in G. sepium. Inoculation with G. desert icola reduced leaf shedding of G. sepium by 50% but did not have the s ame effect for S. siamea. For both tree species inoculated plants extr acted more water from 0-30 cm depth than the uninoculated ones.