集约化种植区硝态氮在土壤剖面中的分布与累积特征

采用GPS定位、土钻取样的方法,在北京市大兴区14个乡镇的农田土壤中选取了91个土壤剖面,分别在0～20cm、20～40cm、40～60cm、60～80cm4个不同深度取得土壤样品,并在一次种植期结束后,综合考虑种植类型和土壤质地后选取24个重复取样点.在此基础上,分析了种植类型及土壤质地对硝态氮分布及累积情况的影响.结果表明,研究区土壤中的硝态氮含量有随土壤深度的增加呈降低的趋势.露地菜田和设施菜田最容易出现硝态氮淋洗现象,果园和粮田的总体状况较好,但粮田个别地区有一定的污染风险,细质地土壤具有较强的保水保肥能力.大兴区采育镇及长子营镇地区有较高的硝态氮累积量,为硝态氮淋洗污染危险区,应进行合理施肥,以免在一个种植期结束后造成较深层土壤中硝态氮的累积.研究结果可为大兴区地下水环境保护提供参考.

Characteristics of nitrate-nitrogen distribution and accumulation in soil profiles at intensive planting areas

By using GPS and soil core sampling, soil samples in the profile of 0~20 cm, 20~40 cm, 40~60 cm and 60~80 cm were collected from 91 sites in 14 towns of Beijing's Daxing district. Repeated samples were collected at 24 sampling pointsbased on planting types and soil texture distribution after a growing period. Effects of planting types, soil texture and crop uptake on nitrate-nitrogen distribution were studied. The results showed that soil nitrate-nitrogen in most of the sampling sites decreased with increasing depth. In terms of planting types, the open vegetable field and protected vegetable field would most likely occur nitrate-nitrogen leaching phenomenon. Orchard and grainfield were better on the whole, and a certain extent of pollution potential was associated with some grainfield soil profiles. Fine soil texture was helpful to preserve water and nutrient. With higher nitrate-nitrogen accumulation, Caiyu and Zhangziying town should be fertilized properly to prevent nitrate leaching deeper into the soil layer. This study provided a reference to protect groundwater in the Daxing district.