Nitrogenaseactivity of azospirillum sp. isolated from rice as influenced by a combination of NH4+-N and an insecticide, carbofuran

Nitrogenase activity in Azospirllum sp. isolated from rice was significantly stimulated following the application of low level of combined N (1 g L−1) and carbofuran at 2 and 5 μg mL−1 Higher levels of either combined nitrogen or carbofuran (above 5 μg mL−1) caused significant inhibition of the nkrogenase activity. Interestingly, inhibitory effect of combined N at 5 g L−1 diminished gradually in the presence of carbofuran (both at 5 and 10 μg mL−1) over a 10 day incubation period. This nullification of inhibitory effects of N by carbofuran in Azospirillum is significant particularly in view of the higher input of agrochemicals in rice.