In order to reveal the changes of organic carbon and nitrogen content of reclaimed soil aggregates in coal mining subsidence areas under long-term fertilization measures

we examined the characteristics of soil aggregates distribution and the changes of organic carbon and nitrogen contents in 4 years and 8 years of reclamation soil under five fertilization measures

which were non-fertilizer (CK)

single application of manure fertilizer (M)

single application of chemical fertilizer (CF)

manure fertilizer and chemical fertilizer (MCF)

biological organic fertilizer and chemical fertilizer mixed fertilizer (MCFB). The results showed that the content of reclaimed soil aggregates first decreased and then increased with the decreasing of grain size

in which the content of aggregates with the size of 3~2 mm was the lowest

accounting for 2%~3% of the total aggregates

and the content of aggregates with the size of 2~1 mm was the highest

accounting for 25%~31%. There was no significant difference in the distribution characteristics of soil aggregates between the 4 years and 8 years of reclaimation under different fertilization measures

but the contents of 7~5 mm and >7 mm aggregates significantly decreased compared with unreclaimed raw soil. The mean weight diameter (MWD) and geometric mean diameter (GMD) of the 8 years reclaimation soil were both higher than those of 4 years

while the fractal dimension (D) value was lower than that of 4 years. The MWD and GMD values of M treatment were the highest

but the D of it was the lowest. The contents of organic carbon and nitrogen in soil aggregates increased with the decreasing of soil aggregate size in reclaimed soil. The aggregates with the size of 0.5~0.25 mm were the highest

while the organic carbon and nitrogen storages in the aggregates with the size of 2~1 mm were the highest

accounting for 24.2%~33.8% and 17.0%~33.1%

respectively. Organic carbon and nitrogen contents were the highest in M treatment

but there was no significant difference in the storages of organic carbon and nitrogen between different treatments. Thus

there was no significant change in the distribution characteristics of soil aggregates and carbon and nitrogen reserves in the 4 years and 8 years reclaimed lands of coal mining subsidence area. The application of manure fertilizer could increase the organic carbon and nitrogen content and the stability of the reclaimed soil aggregates.