Cyanobacterial (unicellular and heterocystous) biofertilization to wetland rice influenced by nitrogenous agrochemical

Abstract

Comparative growth and N2-fixation of cyanobacteria, namely Aphanothece sp. (unicellular) and Gloeotrichia sp. (heterocystous, filamentous), were studied after their inoculation to rice crop in the absence and presence of urea nitrogen fertilizer. In the absence of N-fertilizer application (control), inoculation of both cyanobacterial species showed significant increase in growth and acetylene reduction activity (ARA), but gradual reduction in these parameters was observed at 30 and 60 kg N ha−1 of urea application. In inoculation of Gloeotrichia sp. at control, 30 and 60 kg N ha−1 increased grain yield significantly over uninoculated control in both wet and dry seasons, but grain yield with Aphanothece sp. inoculation was statistically similar to the control at N levels during both seasons. The inoculation study showed that heterocystous cyanobacteria contributed better than unicellular ones, and application of N-fertilizer adversely affected both growth and N2-fixation of native as well of inoculated cyanobacteria. © 2016, Springer Science+Business Media Dordrecht.