NO₃^--N content of groundwater in fields and wells at Tianfu village of Chengdu plain was monitored by using NO₃^--N electrode method for more than one year.Results showed that:a.NO₃^--N concentration of groundwater in fields in winter and spring was higher than that in summer and autumn.The former ranged from 0.36 to 2.62 mg L^-1 with an average of 2.59 mg L^-1,and the corresponding figure for the latter was 0.84~5.48 mg L^-1 and 1.10 mg L^-1,respectively.b.Rate of applied N in wheat cropping season greatly affected NO₃^--N concentration of groundwater in the fields of subsequent rice cropping season.The NO₃^--N concentration of groundwater averaged 17.9 mg L^-1 when N application rate was 375 kg hm²,and the average of NO₃^--N concentration was only 1.3 mg L^-1 when 150 kg hm^-2 was applied.c.NO₃^--N in 3 wells was in the range of 0.14~16.5 mg L^-1 with the mean value of 2.54,3.60,and 6.52 mg L^-1,respectively,higher than the average(1.81 mg L^-1)of NO₃^--N concentration of irrigation water in the region.d.Level of groundwater was not correlated to NO₃^--N content of wells.