Abstract:
Objective To explore the effect of different types and quantities of applied amendments on soil water-stable aggregates and carbon (C) sequestration components in reclaimed soil.
Method A randomized block experiment was set up in the soil for 6 years after reclamation in Tunlan Coal Mine in Gujiao City, Shanxi Province. Two amendments of humic acids and peat were added to the soil with 1%, 3% and 5% of the soil weight in the plough layer (0-20 cm). Samples were taken in the 1st and 2nd years after application, and the soil aggregate composition, soil organic C (SOC) content, components and C sequestration capacity of 0-20 cm soil layer.
Results After applying humic acid and peat after 1 year, the content of > 2 mm soil water-stable aggregates was higher than that of the control. The soil water-stable aggregates were mainly great 0.25 mm in particle size. After 2-year application of amendments, the soil water-stable aggregates were mainly distributed in < 0.053 mm. The SOC content of humic acid treatment was significantly higher than that of peat treatment with equal mass. After 1-year applying amendment, the SOC storage, C sequestration rate of humic acid treatments increased at first and then decreased. The mass fraction of soil > 2 mm aggregates in 1 year after application of amendments was significantly positively correlated with SOC storage, and it was extremely positively correlated with SOC content after 2-year application of amendments. The application of amendments could improve the content of MOC. The POC content showed an increasing trend in 2-year results, while the content of Fe-Al-bonding organic C decreased in reclaimed soil. The application of humic acids and peat could increase the contents of carboxylic acid, alcohols and other functional groups in reclaimed soil, and significantly increase the content of polysaccharide in soil.
Conclusion The additions of humic acids and peat could significantly increase the contents of soil aggregates, SOC, POC, MOC and the ability of soil C sequestration. With the increase of peat and humic acid application, the soil C sequestration rate increases but the soil C sequestration efficiency decreases. After 2-year application of amendments, the macro-aggregate and the SOC of reclaimed soil showed a downward trend, thereby the improvement of reclaimed soil should continue to use humic acids and peat year by year.