Vegetos

Abstract

The diazotrophic cyanobacterial consortium consists of Anabaena variabilis, Aulosira fertilissima, Nostoc muscorum and Tolypothrix tenuis are widely used to supplement chemical N fertilizers for flooded rice cultivation in India. Our present study was undertaken to evaluate the comparative performance of these individual cyanobacterial species on soil fertility and plant growth in rice at three levels of nitrogenous fertilizer. Significant intergeneric differences were observed with respect to nitrogen fixing potential and other N assimilatory parameters under in vitro conditions. Application of individual cyanobacterial species enhanced N uptake and plant carbon content of rice over uninoculated control. Analyses of soil samples after rice harvest revealed significant differences in soil microbial biomass carbon, organic carbon, available N and increase in grain yields with the cyanobacterial inoculants. Yield increase with Anabaena variabilis was comparable with uninoculated control. Correlation coefficient (r) revealed a positive correlation between available nitrogen and soil microbial biomass carbon with N uptake and C content in plants. Our findings revealed functional potential of individual cyanobacterial species in biofertilizer consortia in relation to soil fertility, plant nutrition and yield of rice; however their potential for improving C-N status of flooded rice soils needs to be evaluated at farm level under long-term experimental conditions.