E4 and E6 values of humic acid increased with single application of chemical fertilizer.In the Paddy red soil but they changed a little in Fluvo-aquic soil and Arid red soil.

• 单施化肥也能提高红壤性水稻土胡敏酸的E4和E6值，但对潮土和旱地红壤胡敏酸E4和E6值影响不大。