Evaluation of different application methods of plant growth promoting rhizobacteria (PGPR) on wheat growth in a saline soil

In this research, different application methods of PGPR were evaluated on wheat productivity in a saline soil (EC=5 dS/m) under field conditions. Three strains of Azotobacter, Azospirillum and Pseudomonas bacteria mixed and formulated as PGPR treatment. The experiment was conducted in a factorial randomized block design for two years 2010-11 and 2011-12 in agriculture and natural resources research and education center of East Azarbaijan. The first factor was PGPR application methods in five levels (four PGPR using methods and no- PGPR application) and the second factor was three levels of nitrogen fertilizer treatment (0, 70 and 100 percent of recommended rates of nitrogen). PGPR application methods involved inoculation of wheat seeds with bacteria in autumn sowing (seed treatment), implication of bacteria in spring through irrigation water (fertigation), spraying plant leaves and shoots with bacterial suspension in spring (foliar application) and the combination of those three methods. Combined analysis of data for two years showed that PGPR application methods and nitrogen fertilizer had significant effects on increasing grain yield and biomass production. Using PGPR in seed treatment, fertigation and foliar application methods comparing to control treatments (without PGPR) increased grain yield 45.5, 37.3 and 24.9 %, respectively. The 100 and 70 % of N fertilizer recommendation treatments increased grain production 18.6 and 9.1 % respectively more than control (without fertilizer) treatments.