Molecular changes of ferric oxide bound soil humus during the decomposition of maize straw

Abstract

Background: The mechanism of organic carbon sequestration in different genesis of paddy soils has not been well understood. A 6-month incubation experiment, adding maize straw, was performed in three different genesis of paddy soils and an uncultivated marsh soil. Fourier transform infrared (FTIR) spectroscopy was used to investigate the characteristics of Fe/Al bound organic carbon (Fe/Al-OC) extracted with a mixed solution of 0.1 M NaOH and Na4P2O7 from soils. Results: The function groups of Fe/Al-OC such as phenol-C, amide-C, and C–O groups of polysaccharides were demonstrated by FTIR spectroscopy. Compared to control treatment, the proportion of phenol-C of Fe/Al-OC added maize straw increased with time, but the C–O groups of polysaccharides decreased. Conclusions: These results indicate that polysaccharide groups of Fe/Al-OC mainly contribute to the sequestration of Fe/Al-OC during the primary decomposition stage of maize straw, and the phenol group was stable in different genesis of paddy soils. Both of the polysaccharides and phenol groups were important to C sequestration in paddy soils and marsh soil.