Abstract: According to both different types of vegetation and types of soil, we collected twenty-two soil samples from different regions of the Loess Plateau in order to investigate the distribution of the soil nitrogen in different kinds of soil aggregates. The results indicated that the content of organic nitrogen, mineral nitrogen, ammonium nitrogen and nitrate nitrogen had a descending tendency with the depth of soil layer, no matter the kinds of soil aggregates. The content of organic nitrogen was different in various kinds of soil aggregates, and the content of organic nitrogen appear the shape of a“∧”with the kinds of soil aggregates from >5mm to <0.25mm, there was a peak value at the soil aggregate of 0.25~1mm. There are not obvious distribution pattern of the content of mineral nitrogen, ammonium nitrogen and nitrate nitrogen in different kinds of soil aggregates. The nitrogen stockpiling quantity distribution in different kinds of soil aggregates appear the shape of a“∨”, no matter organic nitrogen, mineral nitrogen, ammonium nitrogen and nitrate nitrogen. The content of nitrogen of every kind of soil aggregate decreases with the increase of latitude in the Loess Plateau, Eum-Orthic Anthrosols is the highest and Ust-Sandiic Entisols is the lowest. Although the content and stockpiling quantity of nitrogen was different in various types of vegetation, there was a same trend, which was: natural forest land >bare land> artificial forest land>farming land.

Key words: Soil aggregates, Organic nitrogen, Mineral nitrogen, Nitrogen pool