日光温室土壤剖面矿质态氮的含量、累积及其分布特性

测定了西安郊区和杨凌地区日光温室栽培番茄生长期间及收获后土壤剖面矿质态氮(铵态氮及硝态氮)的含量,分析了不同形态氮素在土壤剖面的累积及分布情况。结果表明,随着番茄的生长,土壤剖面硝态氮含量逐渐降低,降低的幅度因土壤层次不同而异;土壤剖面铵态氮以3月份含量最高,11月份与5月份相近。番茄收获后土壤剖面残留矿质氮以硝态氮为主,约占土壤剖面矿质氮的比例为80%～90%;残留的铵态氮在土壤剖面的分布相对较为一致。蔬菜生长期间及收获时日光温室土壤剖面硝态氮累积量均表现出在土壤表层相对累积现象,且温室土壤剖面硝态氮的残留量仍高于露地及高产农田。为减少硝态氮淋失带来的环境问题,除合理施用氮肥外,如何减少日光温室蔬菜作物收获后残留硝态氮的淋溶是值得进一步研究的问题。

Mineral nitrogen content and accumulation in soil profiles under sunlight greenhouse cultivation

Mineral nitrogen(NO₃^--N and NH₄⁺-N) content,accumulation and their distribution in 0—100 cm or 0—200 cm soil profiles over the growth period of tomato under the sunlight greenhouse cultivation in the suburbs of Xi'an city and Yangling,Shaanxi was studied.It was found that NO₃^--N content at each layer stepwise decreased with tomato growing;however,the magnitude of decrease in NO₃^--N varied with the depth of soil layers.NH₄⁺-N in March was the highest compared with that in November or May.After the harvest of tomato,the residual mineral nitrogen in soil profile mainly remained in the form of NO₃^--N,accounting for about 80% to 90% of mineral nitrogen in the soil profiles.The distribution of residual NH₄⁺-N in the profiles of soil was rather identical;but higher residual NO₃^--N in soil profiles in the upper layers was observed.The residual NO₃^--N in the profiles of soil under greenhouse cultivation was higher than that under open-field vegetable cultivation or fertile arable fields.It implied that reducing NO₃^--N leaching,optimizing application of nitrogen fertilizer during the growth period of vegetable crops,preventing the leaching of residual NO₃^-N in greenhouse by catch-crop after crop harvest during the rainy season need further study.