Soil water deep
leaching and nitrate(NO~-_3-N) distribution in the soil profile and NO~-_3-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 NO~-_3-N concentration in suction samples were determined.The results indicate that water leaching,NO~-_3-N distribution and leaching losses exhibited pronounced spatial and(temporal) variability.Events of water leaching(and) NO~-_3-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 NO~-_3-N leached below the root zone((including) leaching loss of soil-and fertilizer-N) averaged NO~-_3-N 12 kg hm~(-2) a~(-1)(ranging from NO~-_3-N 6 to 17 kg hm~(-2) a~(-1)) in 1998/1999 and NO~-_3-N 61 kg hm~(-2) a~(-1)(ranging from NO~-_3-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.)