V. C. Patil

VA-mycorrhiza mediated P effect on growth and yield of sunflower (Helianthus annuus L.) at different P levels

A field trial was conducted to study the response of sunflower (Helianthus annuus L.) to different phosphorus levels (16, 24 or 32 kg P ha−1) and inoculation with vesicular-arbuscular mycorrhizal fungus, Glomus fasciculatum on vertisol during summer 1993. At the vegetative stage of sunflower, percent mycorrhizal root colonization, spore count, dry biomass and P uptake did not differ significantly between inoculated and uninoculated control plants. However, at later stages (flowering and maturity) percent root colonization, spore count, total dry biomass and total P uptake were significantly higher in inoculated plants than in uninoculated control plants. The total dry biomass, P content and seed yield increased with increasing P level in uninoculated plants, whereas no significant difference was observed between 16 and 32 kg P ha−1 in inoculated plants. The positive effect of mycorrhizal inoculation decreased with increasing P level above 16 kg P ha−1, due to decreased percent root colonization and spore count at higher P levels.

Effect of pendimethalin on phosphate solubilizing bacteria inoculated to cowpea plants

Summary The influence of pendimethalin, a pre-emergent herbicide, on phosphate solubilizing bacteria Pseudomonas striata inoculated to cowpea plants was studied in pot culture. Pendimethalin exerted inhibitory effects on nodulation, dry matter content of cowpea plants and population of phosphate solubilizing bacteria in the cowpea rhizosphere. However, it did not affect the phosphorus uptake by cowpea plants. Inoculation of Pseudomonas striata enhanced the nodulation, dry matter accumulation and P-uptake in cowpea plants either in the presence or absence of pendimethalin. There was no significant correlation between the number of phosphate solubilizing bacteria in the rhizosphere and P-uptake by the plants.