Effect of the application of pig manure on structural characteristics of fulvic acids in brown soil

The effects of pig manure (PM) on structural characteristics of fulvic acids (FAs) from brown soil were studied in a longterm field experiment The results showed that the O/C ratio, logk and the content of carbonyl-C of FAs all decreased; Whereas, the C/H ratio, RF, the absorption intensity at 2936cm-1 and 1639cm-1, the contents of aromatic-C and alkyl-C of FAs were increased after the application of PM It indicated that the oxidative degree decreased, but the condensation degree and the relative content of aliphatic components increased in the molecule of FAs from brown soil Thus, the molecular structure of FAs tended to become more complex and aliphatic after the application of PM