Abstract: The effect of sewage water irrigation along with the N-fertilizers on NO3 accumulation and on the in vivo NR assay in three leafy vegetable crops were studied. It was found that the NO3 content in the leaves from the experimental sites were around two fold than the control and the NR enzyme activity was comparatively more in the control samples. The in vivo NRA with NaCl treatment increased at low level of NaCl where as with high level of NaCl, the enzyme activity decreased considerably. This is suggestive of the fact that NO3 accumulation may be due to antagonistic effect of chloride ions.