滇池北岸居民-农田混合区域农田土壤氮素空间分布特征研究

Spatial Variability of Nitrogen in Soils in Farmland Adjacent Suburban Villages at Northern Bank of Dianchi Lake

土壤氮含量空间分布特征对评价氮迁移风险和合理施肥具有重要意义。以滇池北岸大清河流域下游46.7 hm2韭菜田与花卉地为对象,于2006年8月通过网格法(40 m×(80～90)m)布点采集112个表层土样,研究了土壤氮素空间变异特征。结果表明,调查区土壤TN为1.28～6.17 g.kg-(1均值3.36 g.kg-1)、NO3--N为3.7～691.7 mg.kg-(1均值89 mg.kg-1)。调查区东北部韭菜种植区由于接受生活污水、养殖废水,土壤总氮含量最高,而西南部韭菜、花卉种植区土壤总氮含量相对较低,高浓度养殖和生活污水的排放是导致土壤总氮含量空间分布差异的主要原因;土壤硝氮含量则以西南部花卉大棚区最高,不同的种植方式(花卉大棚栽培)是土壤硝氮含量差异的主要原因。夏季高温多雨,花卉揭棚将增加土壤硝酸盐淋溶/径流的迁移风险,蔬菜田块土壤氮矿化也可能加剧土壤氮的淋溶/径流迁移。因此,在滇池流域湖滨区居民生活污水、养殖污水的排放,作物种植方式与布局,对农田氮的迁移及水体污染具有重要的影响。

Information about the spatial variability of nitrogen（N）in soils is required for assessing N loss from farmland to water body,and developing rational N fertilizer management practices.In the present investigation,total of 112 top soil samples in a regular grid of 40 m ×（80~90）m were collected from 46.7 hm2 farmlands located at the lower reach of Daqinghe on Dianchi northern bank in Aug.2006.Soil total N ranged from 1.28 g.kg-1 to 6.17 g.kg-1 with an average of 3.36 g.kg-1,and from 3.7 mg.kg-1 to 691.7 mg.kg-1 with an average of 88.7 mg.kg-1 for NO3-N.Geostatistics analysis of these data demonstrated that spatial variability of soil total N,soil NO3-N were obvious.The high soil total N appeared at northeast leek fields,which could be sewage water-driven because northeast fields accepted a large amount of domestic sewage from the adjacent villages;however,high soil NO3-N appeared at southwest flower greenhouse fields,which might be attributed to ex-cessive dosage of N fertilization in flower-fields,and/or nutrients enrichment in top layer soil due to greenhouse effect.The high temperatures and heavy rainy occur in the summer,northeast leek fields may be a risk area for N leaching from soils to water body because of mineraliza-tion of organic N,southwest flower fields could be another risk area for N leaching from soils to water body whenever removing plastic cloth of greenhouse.Present results show that the sewage discharge,crop arrangements and allocation on the lakeshore of Dianchi could have an im-portant influence on loss of nitrogen from farmland to water body,and water quality of Dianchi Lake.