Fertilizer Management Using Plant Growth-Promoting Rhizobacteria in Rice Fields

Afield experiment was conducted at Rice Research Station of Tonekabon, Iran, to determine the effect of seed inoculation with plant growth-promoting rhizobacteria on rice grain yield and yield components under different nitrogen (N) rates. The experimental design was a Randomized Complete Block with factorial arrangement and three replicates. Factors included seed inoculation with plant growth-promoting rhizobacteria [control (un-inoculated), seed inoculation with Azospirillum lipoferum, seed inoculation with Azotobacter chroococcum, and seed inoculation with a combination of A. lipoferum and A. chroococcum] and N rates (100%, 75%, and 50% of recommended nitrogen rates, i.e. 100, 75 and 50 kg N ha-1, respectively). Results showed that the highest grain yield (7875 kg ha-1) was recorded for plants inoculated with a combination of A. lipoferum and A. chroococcum, while the lowest one was recorded for un-inoculated control plants. Moreover, rice grain yield, panicle number per m2, grain number per panicle, and 1000-grain weight increased by 9%, 9%, 18%, and 6%, respectively, as N fertilizer rate increased from 50 to 100 kg ha-1. The highest grain yield (7875 kg ha-1) was obtained when N was applied at the rate of 75 kg ha-1 to seeds inoculated with a combination of A. lipoferum and A. chroococcum