EFFECT OF DIFFERENT PHOSPHORUS AND NITROGEN LEVELS ON DEVELOPMENT OF VA MYCORRHIZA, RHIZOBIAL ACTIVITY AND SOYBEAN GROWTH

The effect of different phosphorus concentrations in the nutrient solution (0.46, 4.6, 23 and 46 ppm P) and one nitrogen levels (8.8 or 17.6 ppm N) on the vesicular-arbuscular (VA) mycorrhiza, the molecular nitrogen-fixing bacteria and growth of soybean (Glycine max. (L.) Merr. cv. Sluna) was investigated. Two endophytes, viz. VA fungus Glomus caledonium and bacterium Bradyrhizobium japonicum strain D 344 were employed. Mycorrhiza was significantly most extensively developed in plant roots growing at deficient phosphorus concentrations (0.46 and 4.6 ppm) at both nitrogen supplies. In the presence of deficient phosphorus and nitrogen levels mycorrhiza significantly stimulated the total N2 fixation resulting in a better growth of mycorrhizal and nodulating plants as compared with nodulating plants without mycorrhiza. © 1990.