Characterization of sulfur-oxidizing bacteria isolated from mustard (Brassica juncea L.) rhizosphere having the capability of improving sulfur and nitrogen uptake.

AIMS: The present investigation was carried out to isolate, screen and characterize potential sulfur-oxidizing bacteria (SOB) isolated from mustard field's soil. METHODS AND RESULTS: A total of 130 bacteria were isolated and after screening five maximum sulfate-producing isolates were optimized for culture conditions. The incubation time of 48 h was found optimum for all bacterial isolates and 30°C was the best temperature for the growth of SSD11, SSR1 and SSG8 whereas 35°C for SSF17. The pH 8 was found best for all four isolates except SSF17 (6 pH). Media having glucose as a carbon source and ammonium sulphate as an N-source were producing maximum sulphate. The isolates SSF17, SSR1 and SSG8 were identified as Burkholderia cepacia (accession no. MT559819), Enterobacter cloacae (accession no. MT559820) and Klebsiella oxytoca (accession no. MT372097), respectively, on the basis of morphological, biochemical and molecular characterization. The isolates were also found to increase N and S uptake efficiently in both wheat and mustard crops. CONCLUSION: This study strongly concludes that SOB isolated from the mustard field can oxidize sulfur in vitro and in vivo conditions. The three best isolates come out of the study were identified as Burkholderia, Enterobacter and Klebsiella strains. Also, inoculation of SOB increased the uptake of S and N nutrient in mustard and wheat crops and thus may be proved as an important plant growth-promoting bacteria having the biofertilization capability. SIGNIFICANCE AND IMPACT OF THE STUDY: As we know, our soil is continuously deteriorating day by day due to excessive utilization and immoderate use of chemical fertilizers. The SOB could minimize the application of chemical fertilizers thus reducing environmental deterioration by improving soil health in sustainable agricultural practices.

Impact of organic fertilizers with and without chemical fertilizers on soil chemical properties and the establishment of nitrogen-fixing bacteria in the rhizosphere.

Effects of organic fertilizers with and without the application of chemical fertilizers for seven years as part of a wheat-pearl millet cropping sequence on soil chemical properties and the establishment of nitrogen fixing bacteria in the rhizosphere were examined. The application of farmyard manure, poultry manure, and sugarcane filter cake alone or in combination with chemical fertilizers improved the soil organic C, total N, P, and K status. Larger populations of Azotobacter chroococcum and Rhizobium leguminosarum biovar trifolii in the rhizosphere of wheat and Egyptian clover respectively, were maintained in soils receiving organic fertilizers either alone or in combination with chemical fertilizers than in soils given chemical fertilizers alone.

Chemical and biological changes during composting of different organic wastes and assessment of compost maturity.

Changes in organic C, total N, C:N ratio, activities of cellulase, xylanase and protease, and microbial population were determined during composting of different organic wastes such as mixture of sugarcane trash and cattle dung, press mud, poultry waste and water hyacinth biomass. There were losses of N in poultry waste and water hyacinth with the effect an initial increase in C:N ratio was observed which decreased later on due to decomposition. The activities of cellulase, xylanase and protease were maximum between 30 and 60 days of composting in various wastes. Similar trend was observed with respect to mesophilic bacterial and fungal population. Various quality parameters like C:N ratio, water soluble C (WSC), CO(2) evolution and level of humic substances were compared after 90 day composting. There was statistically significant correlation between C:N ratio and CO(2) evolution, WSC and humic substances. Significant correlation between CO(2) evolved and level of humic substances was also observed. The study shows that no single parameter can be taken as an index of compost maturity. However, C:N ratio and CO(2) evolved from finished compost can be taken as the most reliable indices of compost maturity.