Plant Rhizosphere Microorganisms Research Articles

The role of rice straw-based hydrogels on some soil microorganisms strains

Due to the shortage in natural conditioners for sandy and sandy calcareous soils, i.e., clays, manures and composts, considerable attention has been paid to use synthesized hydrophilic formulations (hydrogels). For economic and environmental purposes, the present work deals on using rice straw waste (RS) as a substrate for preparation of low cost hydrogels. Four formulations of RS-based hydrogels (G1-G4) were prepared, and applied to desert soil. Their effect on some of the beneficent micro-organisms in plant rhizosphere was evaluated. These microorganisms are: five sps. of Rizobia liguminsorum, Azotobacter chroococcum, Azospirillum Lipoferium), Bacillus supllis ,phosphate dissolving bacteria (Bacellus megatherium), Actinomycetes(Crepresented by streptomyces aureofaciens.) as well as fungi (Aspergillu niger). The results obtained indicate that, the investigated hydrogels have stimulating effect on the studied microorganisms. The hydrogels prepared from using H2O2/ferrous ammonium sulfate as grafting initiation system and neutralizing the final hydrogels by nitric acid provide higher efficiency than hydrogels from grafting by persulfate/persulfite initiation system with the same neutralizing agent. Pre-cyanoethylating the RS promote the efficiency of hydrogel produced from persulfate/persulfite initiation grafting process and the acetic acid to neutralize the final product. This behavior was evaluated through determining the studied microorganisms counts besides dehydrogenase and phosphatase activities in the rhizosphere of 60 days old wheat plants grown in a sandy calcareous soil conditioned with the recom-mended rates of such products, i.e., 0.25-0.5 % on dry soil weight basis. Due to the adverse effect of applying the higher rate of G, i.e., 0.5%, on the aeration of the rootzone, incorporating the lower one (0.25%) in the soil is preferred.

Influences of oyster shell soil conditioner on soil and plant rhizospheric microorganisms

Oyster shell soil conditioner had significant influence on soil and rhizospheric microorganisms in their biomass, respiratory intensity and nutritional requirement. It could stimulate growth of soil and rhizospheric microorganisms, especially nitrogen-fixers, and intensify soil respiration in proportion to the dose and fertilizing time of the conditioner, leading to the increase in the number of nitrogen fixing bacteria and the decrease in the number of bacteria with special nutrition demands.