Abstract: The effect of plant growth-promoting rhizobacteria
(PGPR) on seed germination, seedling growth and yield of field
grown maize were evaluated in three experiments. In these
experiments six bacterial strains include P.putida strain R-168,
P.fluorescens strain R-93, P.fluorescens DSM 50090, P.putida
DSM291, A.lipoferum DSM 1691, A.brasilense DSM 1690 were
used. Results of first study showed seed Inoculation significantly
enhanced seed germination and seedling vigour of maize. In second
experiment, leaf and shoot dry weight and also leaf surface area
significantly were increased by bacterial inoculation in both sterile
and non-sterile soil. The results showed that inoculation with
bacterial treatments had a more stimulating effect on growth and
development of plants in nonsterile than sterile soil. In the third
experiment, Inoculation of maize seeds with all bacterial strains
significantly increased plant height, 100 seed weight, number of seed
per ear and leaf area .The results also showed significant increase in
ear and shoot dry weight of maize.
Abstract: In order to evaluate the relationship between the sulphur (S), glucose (G), nitrogen (N) and plant residues (st), sulphur immobilization and microbial transformation were monitored in five soil samples from 0-30 cm of Bastam farmers fields of Shahrood area following 11 treatments with different levels of Sulphur (S), glucose (G), N and plant residues (wheat straw) in a randomized block design with three replications and incubated over 20, 45 and 60 days, the immobilization of SO4 -2-S presented as a percentage of that added, was inversely related to its addition rate. Additions of glucose and plant residues increased with the C-to-S ratio of the added amendments, irrespective of their origins (glucose and plant residues). In the presence of C sources (glucose or plant residues). N significantly increased the immobilization of SO4 -2-S, whilst the effect of N was insignificant in the absence of a C amendment. In first few days the amounts of added SO4 -2-S immobilized were linearly correlated with the amounts of added S recovered in the soil microbial biomass. With further incubation the proportions of immobilized SO4 -2-S remaining as biomass-S decreased. Decrease in biomass-S was thought to be due to the conversion of biomass-S into soil organic-S. Glucose addition increased the immobilization (microbial utilization and incorporation into the soil organic matter) of native soil SO4 -2-S. However, N addition enhance the mineralization of soil organic-S, increasing the concentration of SO4 - 2-S in soil.