Effect of inoculation of vesicular-arbuscular mycorrhiza on nodulation and phosphorus uptake in cowpea

Abstract

A study on the effect of inoculation of vesicular- arbuscular mycorrhiza and Rhizobium on nodulatlon, phosphorus uptake and yield in coupe a was conducted at College of Agriculture, Vellayani, Trivandrum during 1983-85. Three separate pot culture experiments were conducted during this Investigation; Initially, ten cowpea varieties were screened for the natural incidence of YA-mycorrhiza., There were significant differences between varieties in their mean mycorrhizal index; The infection was maximum in C-152 which had an average index of 1.19. This was significantly higher than that of varieties such as CG-11, HG-22, PTB-1, RC-25, S-488, IT-16 and V-38; The application of rock phosphate had a significant effect in enhancing the mycorrhizal infection in all varieties except in S-488. The cowpea variety which had the maximum mycorrhizal index under natural conditions m s further used to study the effect of age of host plant on mycorrhizal infection. This ms significantly higher on 45th day. The application of rock phosphate at the rate of 30 kg P2 O5/ha had a uniform significant effect in enhancing the mycorrhizal infection at different stages of plant growth. In the last part, a detailed study on the combined effect of VA-mycorrhiza and Rhizobium inoculation on nodulation, phosphorus uptake and yield in cowpea was conducted. Observations were taken at two stages of plant growth, on. 45th day and at the time of harvest. A uniform treatment effect on various plant characters studied was observed only at the time of harvest. The number of nodules formed per plant and their fresh (and dry weights were significantly higher in the treatment combination consisting of the standard culture of VA-mycorrhiza, Rhisobium inoculation and the application of rock phosphate at the rate of 30 kg P205/ha. The fresh and dry weights of plants and the mean mycorrhizal index were also maximum in this (MSR+RP) treatment.