Abstract:

The research selected five land-use types in the Guanmenshan watershed in northwest Guizhou to study the distribution characteristics of soil total nitrogen (N) and nitrate-N under different land-use types using the chemical analysis of soil samples. The results showed that:total N and nitrate-N concentration in the surface soil of shrub land were greater than that in arbor land. Total N in middle and bottom of slope was higher than that in top of slope. Nitrate-N in slope top, slope middle and slope bottom of shrub land decreased with increasing soil depth, and nitrate-N in the top and middle of slope accumulated near 60~80 cm soil layer but did not appear in the bottom of slope in arbor land. Total N was the highest at 0~20 cm soil layer in five land-use types and decreased with increasing soil depth. Soil nitrate-N reduced with increasing soil depth in shrub land, corn field and abandoned land, but accumulated in 60~80 cm soil layer in arbor land and accumulated in 20~40 cm and 60~80 cm soil layers in orchard. Residual rates of soil nitrogen and nitrate-N were the highest in 80 cm deep soil in orchard, and were 12.18×10³and 352.0 kg·hm^-2, respectively. The differences of Residual N amount were not significant under different land-use types, but residual nitrate-N in orchard and corn soil were significantly higher than other types.

Key words: Northwest of Guizhou, Watershed, Land-use types, Total nitrogen, Nitrate-N

摘要：

在黔西北关门山小流域选取5种不同的土地利用类型，通过对其土壤样品进行化学分析，研究不同土地利用类型下土壤全氮及硝态氮的分布特征。结果表明：灌木林地表层土壤全氮和硝态氮含量高于乔木林地。乔木林地和灌木林地坡中和坡脚土壤剖面上的全氮明显高于坡顶。灌木林地的坡顶、坡中和坡脚土壤硝态氮随着深度的增加而降低，乔木林的坡顶和坡中土壤硝态氮在60~80 cm土层处出现累积，但坡脚没有；5种土地利用类型中，土壤全氮含量均以0~20 cm土层最高，随着土壤深度增加迅速降低。灌木林地、玉米地和撂荒地土壤的硝态氮随着土壤深度的增加而降低，但乔木林地硝态氮在60~80 cm土层累积，果园硝态氮在20~40 cm和60~80 cm土层累积；80 cm厚土体中残留的土壤全氮和硝态氮以果园最高，分别为12.18×10³和352.0 kg·hm^-2，不同土地利用类型间土壤全氮残留量差异不显著，但是果园和玉米地的硝态氮残留量显著高于其他土地利用类型。

关键词: 黔西北, 小流域, 土地利用类型, 全氮, 硝态氮