Diversity of diazotrophs in tropical rice field under the influence of organic and nitrogen fertilization

The diversity of diazotrophic community of two different rice field of typical tropical rice agroecosystem under long-term application of nitrogen and organic fertilizer was studied. Most probable number (MPN) result revealed that organic fertilizer amended rice field (O) have higher diazotroph population than nitrogen fertilizer amended rice field (N). NifH gene based restriction fragment length polymorphism (RFLP) analysis revealed presence of uncultured diazotroph, Anabaena, Rhizobium, Nostoc, Azospirllium, Methylobacter, Leptolyngbya and Sinorhizobium. Diversity index of diazotroph was found higher in O soil. The study suggested that application of nitrogen fertilizer adversely affected community composition of diazotroph in comparison to organic fertilizer and the differences were found significant.