Effect of Phorate on Nitrogen Fixation by Blue-Green Algae

The effect of phorate (insecticide) on nitrogen fixing blue-green algae, Nostoc muscorum and Nostoc piscinale was studied in liquid as well as soil culture systems. The fixation of nitrogen and chlorophyll content of these algal cultures were markedly increased by the application of the insecticide at lower concentrations. Nostoc muscorum was more efficient than N. piscinale and performed well up to 50 μg/ml in liquid culture and at most levels (up to 250 μg/g) of insecticide application in soil culture. The toxicity of higher concentrations of insecticide was found to be gradually reduced on prolonging the growth period of the algal species. Higher concentrations up to 250 μg per g soil andjor per ml medium were less lethal in soil culture than in liquid medium for both the algal species.