Soil water deep leaching and nitrate(NO₃^--N)distribution in the soil profile and NO₃^--N leaching losses below the root zone were investigated in fields under a local traditionally managed wheat-maize crop rotation system in the North China Plain.Coupled with the soil water balance method,soil water deep leaching and NO₃^--N concentration in suction samples were determined.The results indicate that water leaching,NO₃^--N distribution and leaching losses exhibited pronounced spatial and temporal variability.Events of water leaching and NO₃^--N leaching loss were prone to occur during the summer maize growing season(rainy season),after each irrigation operation and significant rainfall.Annual soil water deep leaching reached 33～48 mm(averaged 39 mm)in 1998/1999 cropping year and 90～92 mm(averaged 90.7 mm)in 1999/2000,accounting for 10% and 19% of the total amount of irrigation plus rainfall,respectively.The amount of NO₃^--N leached below the root zone (including leaching loss of soil-and fertilizer-N)averaged NO₃^--N 12 kg hm^-2 a^-1(ranging from NO₃^--N 6 to 17 kg hm^-2 a^-1) in 1998/1999 and NO₃^--N 61 kg hm^-2 a^-1(ranging from NO₃^--N 30 to 84 kg hm^-2 a^-1)in 1999/2000,equivalent to 1.4%～4.1% and 7.3%～20.3% of the N fertilizer applied,respectively.The results indicate that during the summer maize growing season,potentials do exist of reducing water and fertilizer inputs,so as to improve water and fertilizer use efficiency in this region.