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(-1). 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-1. The shallow groundwater of the study region, combined with poor water and NO3- management practices, are creating a long-term legacy of contamination.