Journal of the Indian Society of Soil Science

Studies on the effect of slow release nitrogenous fertilizers on the fixation of nitrogen by blue-green algae (BGA) and the changes in the contents of different nitrogen fractions in soils revealed that BGA (Aulosira fertillissima) inoculation caused about 5 per cent increase in the total nitrogen content of Bolpur (Rhodustalf, pH 6.5) and Cooch Behar (Fluvaquent, pH 5.4) soils. Among the fertilizer treatments, urea recorded the highest increase in total N due to inoculation followed by lac-coated urea whereas the increase was lowest by crotonylidene diurea. Application of N sources fncreased both inorganic and organic fractions of soil nitrogen. The amounts of easily available forms of nitrogen such NH_4⁺-N, NO_3⁻ + NO_2⁻ - N and hydrolysable ammonium + amino sugar-N were comparatively less in presence of inoculation than in its absence, irrespective of soils and fertilizer treatments. Those forms might have been assimilated by BGA as hydrolysable organic N which was, however, more in presence of inoculation.