BEHAVIOR OF VESICULAR-ARBUSCULAR MYCORRHIZAL FUNGI IN ANDO-SOIL AND THEIR ROLES ON CROP GROWTH

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1. Behavior of VA mycorrhizal fungi in University farm field - humus rich Ando-soil - was studied in relation to the differences in agronomic practices. Total number of VAM fungus spores (>53 um) collected from forage crop field was around 400-600 per 100g air dry soil, in which Gromus spp. occupied more than 99%, whereas only a few numbers of Gigaspora margarita and Scutellospora gregaria were detected. Though several differences in species of Gromus spp. were recognized, those were not yet identified. 2. The effects of continuous application of farmyard manure and phosphatic fertilizer on VAM infection and the growth of maize and winter wheat were examined. Farmyard manure and phosphatic fertilizer decreased additively the VAM infection on both crops, in which maximum infection reached up to 45-50 % at silking stage of maize and at reproductive stage of wheat. Positive coorelations between VAM infection % and P % in shoots were observed at the stage of maximum infection. However, the … More interrelationships between VAM infection % and dry weight of shoots whenever shown in significance were always negative. 3. Mulching with polyethylene film promoted the soybean growth through higher temperature in surface soil (increase in about 5-10 c), inducing in P absorption at earlier stage due to accerelation of VAM infection as well as the increase in nodule formation. Charcoal application to the soil also enhanced VAM infection through preparing favorable micro-environment for VAM fungi in rhizosphere, resulting in increase in plant growth under not only low, but relatively higher fertility condition. 4. The one of Gromus spp., not yet identified (surface colour of spore was yellow), isolated from forage crop field stimulated extremely soybean and chickpea growth in pots with sterilized Ando-soil having 63.3ppm of Bray II-P, resulting in more than 300% in grain yield and 500% in P in shoots as compared with control, whereas there was no significant promotion in wheat and maize growth, indicating that there may be some host specificities among VAM fungi. Few resposes of soybean and chickpea to Gigaspora margarita were observed under the same condition. 5. Continuous application of herbicides (3 years) to the soil decreased VAM fungus spores only when non-mycrrhizal crops (cabbage) were continuously cultivated. Less