太湖水网地区不同种植类型农田氮素渗漏流失研究

Study on nitrogen leaching in farmlands with different crops in riverine plain area of Taihu Lake

为了探索太湖流域水网地区不同种植类型农田土壤中氮素累积量与渗漏水中氮素含量之间的关系,在浙江省嘉兴市选择10个农田点位埋设渗漏计和地下水采集管,采集水、土样品,研究了菜地、果园和水田3种典型种植类型农田氮素渗漏流失情况。结果表明:1)旱作农田渗漏水中的NO3--N含量在汛期明显高于非汛期,菜地在汛期和非汛期时20 cm渗漏水中的NO3--N含量分别为51.70 mg.L-1和12.53 mg.L-1,果园在20 cm渗漏水中的NO3--N含量在8至9月份高达125.51 mg.L-1,水田20 cm渗漏水中的NO3--N含量在汛期和非汛期差别不大,分别为2.17 mg.L-1和1.60mg.L-1。2)研究区菜地和果园等高施肥量农田土壤中的无机氮含量和渗漏水中的氮素含量均显著高于水田。农田土壤中NO3--N累积量与渗漏水中氮素含量之间具有极显著的正相关关系,表明农田土壤中高水平的NO3--N累积量必然增加氮素渗漏流失的风险。

In order to explore the relationship between the nitrogen （N） accumulation in soil and the N content in leaching water in farmlands with different crops in Taihu Lake Watershed, a series of field trials were carried out by fixing pumping water equip- ments on farms in Jiaxing, Zhejiang Province. 10 farmlands of 3 types were selected and water and soil samples were collected and analyzed. The results showed that： NNO3^--N content in leaching water of vegetable fields and orchards in flood seasons was higher than that in non-flood seasons. The content of NNO3^--N in 20 cm leaching water was 51.70 mg ·L-1 and 12. 53 mg ·L-1 in flood seasons and non-flood seasons respectively in vegetable fields. The content of NNO3^--N reached as high as 125.51 mg ·L-1 in Au- gust and September in 20 cm leaching water of orchards. The content of NNO3^--N in 20 cm leaching water was 2. 17 mg·L-1 and 1.60 mg·L-1 in flood seasons and non-flood seasons respectively in paddy plots. There was almost no difference in different sea- sons in paddy plots. The N accumulation in soil layers and N content in leaching water of vegetable fields and orchards were much higher than that of paddy plots. There was a significant positive relationship between NNO3^--N content in soil layers and N content in leaching water, which indicated that N accumulation in soil must cause N leaching loss and the more NNO3^--N accumulated in soil, the more N leached from the farmlands.