The effect of inoculation with Streptomyces and phosphorus fertilizer rate on biologic yield, grain yield and yield components in wheat and barley

Usually, phosphorus after nitrogen is the most important mineral nutrient limiting growth and yield of crops. Phosphate solubilizing rhizobacteria can change non-absorbable forms of phosphorus to absorbable forms. To evaluate the effect of inoculation with Streptomyces sp. bacterium and phosphorus (P) fertilizer rate (0, 20, 40, 60 and 80 kg P per ha) on yield and yield components in wheat (variety Morvarid) and barley (variety Sahra ), a pot experiment was conducted as factorial arrangement in a completely randomized design with four replications in new site of Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran, during 2014-2015 growing season. Results of this study revealed a significant linear increase in grain yield of wheat and barley by increase in the fertilizer phosphorus rate. The results showed that grain yield in control treatment (without P fertilizer) was 9.8 gr per pot (2352 kg.ha-1), but with increasing one kg P fertilizer, grain yield increased to 0.13 gr per pot (26 kg.ha-1). With the use of 80 kg.ha-1 P fertilizer, grain yield increased to 20.2 gr per pot (4848 kg.ha- 1), that represents a 106% increase in grain yield than the control treatment. The results showed that increasing grain yield in barley was mainly due to increase in the number of spike per plant and the number of spikelet per spike, but in wheat mainlt due to increase in the number of spikelet per plant and number of grain per spikelet, and the role of grain weight in the changes of grain yield was negligible. Also, the findings of this study showed a linear increase in plant biologic yield due to the use of P fertilizer rate, bacteria inoculation and their interactions. The results clearly showed that the effect of inoculation on the plant growth in the lower amounts of phosphorus fertilizer was more than the higher amounts of phosphorus fertilizer.