Effects of agricultural activities on nitrate contamination of groundwater in a Yellow River irrigated region

Agricultural-induced increase of nitrate (NO3) loading in groundwater is a worldwide problem. This study investigates the impacts of agricultural activities on groundwater NO3 pollution in a Yellow River irrigated region. The agricultural land use patterns are dependent on the land and water conditions. Besides wheat–maize rotation, the most popular cultivation pattern, other patterns with high production/ income, such as greenhouse vegetables, watermelon–cotton, are also widely adopted. N-fertilizer is excessively applied for all land-use patterns, with the annual amount ranging from 500 to 1420 kg N ha. The NO3 loading in groundwater has large seasonal variation mainly caused by agricultural activities. Even in the best water quality season, 4 out of 27 samples show NO3 concentrations in excess of the drinking water standard, with a maximum NO3 concentration in well water of 100 mg NO3 L. The shallow groundwater of the study region, combined with poor water and NO3 management practices, are creating a long-term legacy of contamination.