Vol. 3 No. 1
Effect of diazotrophs on the mineralization of organic nitrogen in the rhizosphere soils of rice (Oryza sativa).
Author(s): A. C. DAS AND D. SAHA
Abstract: A field experiment was conducted during 2002 to investigate the effect of inoculation of 2 non-symbiotic N2-fixing bacteria, Azotobacter (strain AS8) and Azospirillum (strain AM1), in presence of 50 kg N ha-1 and 5 t FYM ha-1 on the performances of the diazotrophs with respect to transformation of organic nitrogen in the rhizosphere soils of rice (Oryza sativa L, cv. PNR-381). Inoculation of the diazotrophs substantially increased the content and availability of different fractions of organic (hydrolysable and non-hydrolysable) nitrogen in the rhizosphere soils resulting in greater yield of the crop. In general, combined inoculation of the diazotrophs was most stimulative in augmenting the nitrogen status of the rhizosphere soils, which was comparable to the effects under the uninoculated soils receiving 100 kg N ha-1 as urea-N. Between the two organisms, Azotobacter was more effective than Azospirillum in relation to accumulation and transformation of different fractions of organic nitrogen content in the rhizosphere soils. All the fractions of hydrolysable organic nitrogen (hydolysable NH4 +, hexosamine, amino acid and unidentified hydrolysable organic-N) decreased with a concomitant increase in non-hydrolysable fraction with the age of the crop.
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