INFLUENCE OF GREEN MANURES ON MYCORRHIZAL COLONIZATION AND YIELD OF SWEET-POTATO

This study was carried out in an arenic albaquult soil aiming to evalu ate the effect of different green manures and fallow on indigenous VAM fungal inoculum potential and sweet potato (Ipomoea batatas) yield. T he treatments were: no vegetation, fallow, sun hemp (Crotalaria juncea ), jack bean (Canavalia ensiformis), pigeon pea (Cajanus cajan), and v elvet bean (Mucuna aterrima). Jack bean and velvet bean had a greater shoot accumulation of N, P and K than other treatments. Previous culti vation with leguminosae increased sweet potato yield over fallow. The leguminosae incorporation into the soil reduced spore population in no vegetation, jack bean and pigeon pea when compared with fallow. Howev er, sun hemp, velvet bean and jack bean had a greater number of infect ive propagules than no vegetation. The root colonization of sweet pota to was greater in sun hemp, velvet bean and fallow when compared with no vegetation. The sweet potato yield was directly correlated with the amounts of N, P and K founded in the green manures mass.