Abstract:To control nitrogen (N) leaching loss from protected vegetable production fields and minimize the risk of N pollution of groundwater in the Tai Lake region, China, a field experiment was conducted to evaluate the effects of different rotation patterns and fertilizer application rates on nitrogen leaching loss using lysimeters. Soil NO-3-N concentration, electrical conductivity and pH values were also analyzed. There were two types of rotation patterns, pattern 1 (celery-tomato-lettuce) and pattern 2 (burclover-tomato-lettuce), and two N levels, the conventional N application rate (N1) and reduced N application rate (N2). Comparison with the rotation pattern 1, the averageNO-3-N concentrations in the leachate of the rotation pattern 2 are decreased by 36% (N1) and 38% (N2), and the total N leaching under the two N treatments decreased by 41% and 38% respectively, although the leachate volumes are not affected by the rotation pattern or N application rates. The optimum way to control the N leaching loss is a combination of the rotation pattern 2 and the reduced N application rate (N2). For example, the total annual N leaching loss is 63.0 kg/ha under the combined treatment, and an economic return (up to 519 thousand Yuan/ha) is achieved, which is an increase of 29%. After growing three vegetable crops in a year, soil NO-3-N concentration in the topsoil (0-20 cm) is 189.2 mg/kg in the N1/rotation pattern 2 combination, whereas it is 269.3 mg/kg in the N1/rotation pattern 1 combination. In addition, the rotation pattern 2 reduces soil NO-3-N content by 30% (N1) and 26% (N2) respectively, and soil pH and electrical conductivity are reduced significantly (P＜0.05). In the Tai Lake region, rotation patterns requiring less N input (e.g., bur clover-tomato-lettuce) could be practiced to reduce N leaching loss and achieve greater economic return.