Effect Of Different Fertilization And Planting Patterns On NO₃^- -N Accumulation In Soil Around Baiyangdian Lake

According to the situation of agricultural non-point source pollution in BaiYangdian Lake, this study was conducted for agricultural soils under different land uses around Baiyangdian lake. The field plot experiments were set up to investigate nitrate concentrations and distribution in soil profiles under different fertilization and different nitrate levels throughout sampling soils and soil solution in soil multi-layers around Baiyangdian Lake. Moreover, the effects of different planting patterns (wheat and maize monocropping /maize-soybean intercropping) were also studied to explore the leaching of nitrate in soil system.The results showed as follows:1 In different optimal fertilization experiments, the amount of fertilizer N should be less than 225 kg/hm², P₂O₅ within 90-180 kg/hm² and K₂O 90 kg/hm² for winter wheat growing in MaPu (fertility level was low); the amount of fertilizer N should be controlled within 90-135 kg/hm², P₂O₅ in 60-90 kg/hm², and K₂O 60 kg/hm² for winter wheat in ZhangLiu (fertility level was high). The maize yields and NO₃--N accumulation in optimal treatment were better than conventional treatment on summer maize. In MaPu site, the yields in treatment of the one-time basal compound fertilizer were significantly higher than that of the mixed fertilizers treatment (CO(NH₂)₂, (NH₄)₂HPO₄,KCl), which had no effect on maize yields and nitrate accumulation in soil of ZhangLiu.2 Different N-fertilizer application levels had an impact on the NO₃^--N concentration in soil profile. NO₃^--N mainly accumulated in 0-30 cm soil layer. ConN and OptN+30% lead to NO₃^--N accumulations significantly higher than OptN in 0-90 cm soil layer. NO₃^--N concentration in soil solution of ConN and OptN+30% was high.Excessive N fertilizer supply increasethe risk of NO₃^--N leaching in soil. Considering the yield and environmental effect comprehensively, the nitrogen application rates of 180 kg/hm² and 200 kg/hm² were better for summer maize and winter wheat, respectively. 3 The yields of maize in maize-soybean intercropping system were significantly higher than that of monocropped maize. The NO₃^--N concentrations in soil solution of soybean field at 0-30 cm were significantly higher than the intercropped maize and ConN treatment, while the nitrate concentrations at 30-90 cm were much lower. The economic and environmental benefits of maize-soybean intercropping system were higher than that of monocropping maize.4 The suitable N application level significantly increased the yields, 1000 grain weights, grain numbers per ear and N-fertilizer use efficiency. The crop yield in the control was lower markedly than that of other treatments. The optimal treatment could make higher yield and might reduce the amount of N fertilizer application and N negative effects on water environment of the lake.