Nitrate in soil profiles and nitrate pollution of drinking water in the Loess region of China

Chemical nitrogen fertilizers have greatly increased crop yields in China during the last 20 years. However, in Mizhi town, Shaanxi Province, large applications of nitrogen fertilizers have resulted in unacceptably high concentrations of nitrate in drinking water. The present investigation of nitrate concentrations in soil water revealed very high concentrations in fields on the valley bottoms, but comparatively low concentrations on hilltops and slopes. The 200-400 cm soil layer, had 272 kg NO3-N ha(-1) on "stepped land" and 172 on "bottom land". The flow of water through the soil profiles was about 2 m yr(-1) If there is no uptake of nitrate by roots below 200 cm depth, valuable nitrogen fertilizers will be leached out from the soil profiles in amounts corresponding to an annual loss per ha of about USD 148 and USD 94 for stepped land and bottom land, respectively.