京郊典型农田土壤易流失氮素组分及含量特征与差异

The Characteristics of Easy-loss Nitrogen Fractions in the Soil Suspension from Typical Cropland in Beijing Suburban,China

通过测定京郊连续冬小麦-玉米大田和不同种植年限菜地表层土壤悬浮液氮素组分及其含量,模拟测定土壤易流失氮素组分,从而为氮素高效管理提供基础数据。结果表明:菜园土壤有机质、全氮、全磷、有效磷、矿质氮等指标大大高于大田土壤,且表现出明显的酸化现象。大田和菜地土壤悬浮液均含有可观的氮素:悬浮液总氮(TSN)为124.42～355.41 mg.kg-1,其中大田土壤一半左右为颗粒状氮,而菜地土壤2/3以上为可溶性氮;可溶性全氮(TDN)范围为55.53～220.51 mg.kg-1,其中主要是可溶性无机氮(DIN),范围为28.00～171.92 mg.kg-1,可溶性有机氮(DON)为27.53～81.74 mg.kg-1;颗粒状氮(PN)为70.90～134.90 mg.kg-1。各种氮素组分及其含量,菜地土壤远远高于大田土壤,且随着蔬菜种植时间的延长差异扩大。京郊菜地土壤氮素流失风险极大,对水体构成巨大的威胁。

The nitrogen fractions in the soil suspension,named as easy-loss nitrogen fractions was determined in order to estimate the maximum loss capacity of nitrogen from the typical croplands in Beijing suburban,and then supply basic data for effective nitrogen management.The results showed that the soils from vegetable land（VL） contained much higher organic matter,total nitrogen,total phosphorus,Olsen-P,mineral nitrogen and low pH value,compared with the soils from the continuous winter wheat-corn land（WCL）.All the soils from either VL or WCL contained considerable amount of total suspension nitrogen（TSN）,ranging from 124.42 mg·kg-1 to 355.41 mg·kg-1.About half of TSN in WCL was particulate nitrogen（PN）,but more than 2/3 in VL was dissolved nitrogen（TDN）.The total dissolved nitrogen ranged from 55.53 mg·kg-1 to 220.51 mg·kg-1.Most of TDN was the dissolved inorganic nitrogen（DIN）,ranging from 28.00 mg·kg-1 to 71.92 mg·kg-1.The dissolved organic nitrogen（DON） was 27.53~81.74 mg·kg-1.Particulate nitrogen（PN） was 70.90~134.90 mg·kg-1,All the different forms of nitrogen in soil suspension were much higher in VL than WCL.The longer cultivation of vegetable,the larger difference in the concentrations of different nitrogen components was found between VL and WCL.Our results imply very high risk of nitrogen losses from the croplands of Beijing suburban,which may produce high potential contamination to waterbody in this region.