Effects of plant growth promoting microorganisms inoculums on mineral nutrition, growth and productivity of rice (Oryza sativa L.)

Two field experiments were carried out separately to evaluate the ability of three plant growth promoting microorganisms (PGPM, Pantoea ananatis, Enterobacter sp. and Piriformospora indica) as bio-fertilizer on rice (Oryza sativa L.) productivity under different levels of potassium sulfate fertilizer (PSF). The results clearly showed that the PGPM significantly enhance the dry weight of rice plant tissues as compared with the control. Uptake of phosphorus and potassium in rice plant tissues and also nutrient use efficiency (NUE) remarkably increased especially when the co-inoculation with P. ananatis and P. indica in experiment I and the combined (seed + seedling root) inoculation method in experiment II were used. Grain yield (GY) increased linearly with the addition of PSF up to 110 kg ha(-1) for the co-inoculation treatment (23% lower than the control), then remained constant at its maximum (5348 kg ha(-1), 32% higher than the control) up to 180 kg ha(-1) in experiment I. Similarly, the maximum value of GY (5330 kg ha(-1), 20% more than the control) was obtained at 100 kg ha(-1) PSF in experiment II. Consequently, both co-inoculation and combined inoculation methods could be selected as the best ways for improving NUE and plant growth of rice in sustainable production systems.