Abstract: In this paper, black soil samples were separated into four sizes (>2 000, 2 000-250, 250-53, and <53 μm) of aggregates by wet sieving, and their free light fraction (free LF) and intraaggregate particulate organic matter (iPOM) were isolated by density fractionation, aimed to evaluate the effects of manure application on the organic carbon in different sizes of aggregates in black soil. The results showed that compared with the control, applying manure improved soil aggregation significantly, and compensated the disturbance of tillage and slowed down the turnover of aggregates to some degree. After applying manure, the content of fine iPOM-C was significantly higher than that of coarse iPOM-C, suggesting that manure application was beneficial to the accumulation of fine iPOM-C, which is the main form of carbon sequestration in the aggregates of black soil.

Key words: chlorophyll fluorescence, PSⅡ, CO₂ concentration, Japonica rice