Relationships between the Size of Aggregates, Particulate Organic Matter Content, and Decomposition of Plant Residues in Soil
В. М. Семенов, Т. Н. Лебедева, N. B. Pautova, D. P. Khromychkina, I. V. Kovalev, Н.О. Ковалева
Abstract
The distribution of total organic matter (Corg), particulate organic matter (CPOM), and potentially mineralizable organic matter (C0) in mega- (10–5 and 5–2 mm), macro- (2–0.25 mm), and microaggregates (<0.25 mm) isolated by dry sieving from gray and agrogray soils (Luvic Retic Greyzemic Phaeozems) of different land uses was studied. In the soils under forest and meadow, the highest Corg content was detected in the megaaggregates of 5–2 mm in size (43 and 37% of Corg in whole soil sample, respectively), whereas in the arable soil, it was found in macroaggregates (45%). In the uncultivated soil, the CPOM was mainly accumulated in megaaggregates (65–72% of the CPOM in the whole sample); in the arable soil, it was equally distributed between mega- and macroaggregates (46–45%). The fine (0.25–0.05 mm) CPOM subfraction in the uncultivated and arable soils contained 1.3- and 2.3-fold more carbon, respectively, as compared with the coarse (2–0.25 mm) CPOM subfraction. The C0 content in the aggregates correlated with CPOM and Corg. Decomposition of plant residues with a wide C : N ratio in soil increased with a decrease in the aggregate size. However, aggregate size did not influence the decomposition of plant residues with a narrow C : N ratio. The effect of aggregate size on the decomposition rate mainly appeared at the early stages of transformation of plant residues.