摘要： 北方大部分地区的旱地土壤中，农业氮素一般表现亏损，平衡强度约87%；园田土壤氮素略有盈余，平衡强度约123%¹⁵示踪研究表明，旱地土壤主要作物氮素利用率平均为27.04%，土壤残留24.79%，亏缺损失48.17%。园田主要蔬菜氮素和用率平均为29.11%，土壤残留22.67%，亏缺损失48.23%，其间差异很小。北方旱地施用铵态氮化肥主要损失是氨的挥发。影响氨挥发的因素有风速、温度、土壤水分、土壤质地、化肥品种。氮肥深施是防止氨挥发的有效方法。

关键词: 旱地土壤, 氮素平衡

Abstract: As the nitrogen balance study shows,the crop field soil in Tianjin suburbs,for the most part,presents nitrogen deficiency with a balance coefficient of about 87%.whereas the vegetable soil has an excess with a balance coefficient ofabout 123%.The result of study using 15N stable tracer isotope tells us that for crop field soil,the nitrogen utilization ratio of mam crops averages 27.04%,residue in soil is 24.79% and deficits take 48.17% yet for vegetable soil,the nitrogen utilization ratio of main vegetables averages 29.11%,residue in soil is 22.67%.and deficits take 48.23%.Small differences exist between those of crops and of vegetables.The main deficiency of ammonium nitrogen fertilizen applied to the crop field soil in Tianjin suburbs is due to ammonia volatility,which is mainly influenced by the factors of wind speed,temperature,soil moisturs' soil texture,and fertilizfr types.And the effective way of preventing ammonia from volatilization is deep placement.

Key words: Crop field soil, Nitrogen balance