污水灌溉区土壤非饱和带氮分布特征

以徐州市铜山区奎河段两岸的农业灌溉区为例,结合当地典型的4种不同种植方式,对非饱和带土壤中的硝酸盐氮和铵氮质量比及其分布特征进行分析。结果表明:土壤中硝酸盐氮质量比为3.8~128.1mg/kg(平均33.0mg/kg),铵氮质量比为2.3~5.7mg/kg(平均3.8mg/kg);非饱和带土壤中氮主要来自常年施肥和污水灌溉;由于不同种植方式具有不同的施肥和灌溉条件,因此土壤中氮的分布亦不同;在接受地表灌溉和施肥补给之后,硝酸盐氮主要以下渗迁移为主;铵氮在下渗过程中会产生吸附作用,其质量比与土壤中黏土颗粒的含量呈一定的相关性,但在常年灌溉的水稻-冬菜种植点,在表层土中尽管黏土颗粒含量不高,铵氮质量比仍然较高。

Distribution characteristics of nitrogen in the unsaturated soil of sewage irrigation area

The content and distribution of nitrate and ammonium in the unsaturated soil were analyzed in this study, considering four kinds of typical planting patterns on both sides of the agricultural irrigation area of Kuihe River in Tongshan District of Xuzhou City. The analysis results of the soil leaching liquor, which was obtained from the situ soil sample, show that the content of nitrate vary from 3. 8 to 128. 1 mg/kg with an average of 33. 0 mg/kg and the content of ammonium vary from 2. 3 to 5. 7 mg/kg with an average of 3. 8 mg/kg. The annual fertilization and sewage irrigation is the main source of nitrogen in the unsaturated soil. Meanwhile, the distribution of nitrogen in the soil is controlled by the condition of fertilization and irrigation for different planting patterns. Furthermore, the nitrogen is recharged by the surface irrigation and fertilizer, and mainly migrates in the direction of down-gradient of soil column. The ammonium is absorbed in the process of infiltration and as a general rule, the content of ammonium is related to the number of clay particles. However, the content of ammonium is still at a high level in the planting area of rice and cabbage with annual irrigation, even though the number of clay particles is small near the soil surface.