The nature of organic carbon and total nitrogen distribution in the fractions of leached chernozem aggregates and gray soil in Western Siberia

Abstract

The features of the accumulation and distribution of organic carbon and nitrogen in the aggregates of the arable layer of leached chernozem (Luvic Voronic Chernozems) and gray forest soil (Luvic Retic Greyzemic Phaeozems) were evaluated. After dry sieving in structural separates of dimensional fractions >10, 10-5, 5-2, 2-1, 1-0.25, and <0.25 mm, the content of organic carbon and total nitrogen was determined in the laboratory. It was found that chernozem and gray forest soil significantly differed from each other in organic carbon in all fractions of structural separates. Lumpy aggregates (>10 mm) and fine earth (<0.25 mm) were characterized by an average spatial variability (CV up to 21%) of organic carbon and total nitrogen content. In chernozem arable layer, the maximum content of organic carbon and total nitrogen was in size fractions from 5 to 0.25 mm, whereas in gray forest soil – from 10 to 2 mm. Maximum value of C:N in gray forest soil was 16.0 units in aggregates with dimensions less than 0.25 mm, and in chernozem – in the lumpy fraction (> 10 mm), where the ratio was 15.1 units it was revealed that the content of organic carbon in structural units depends on the soil type by 21%, and on the dimensional fraction by 37%. The total nitrogen content is determined by 20% by the soil type and 36% by the size of structural aggregates.