[Effect of different tillage managements on black humic fractions and IR spectral feature]

The present study was based on the long-term (10 years) field conservation tillage experiment, in which four tillage treatments were designed as following: Conventional tillage (CT) by moldboard plowing with ridge culture; Rotary tillage with ridge culture (RT); Alternant tillage by rotary on wide row and loosing on narrow row (WN); Rotary tillage plus deep loosing annually (RD). Humic acids were extracted from black soil profiles under these tillage managements. The elements visible spectra and FTIR of HA in black soil were analyzed. The results indicated that the elements of HA were affected by different tillage managements, WN increased N/C, H/C and O/C values of HA in the 0-20 cm layer. The lowest E4/E6 value of HA was found under CT treatment, while the highest E4/E6 value was found under WN treatment; FTIR indicated that CT treatment increased the amount of C=N groups and aromatic ring condensation of HA in 0-20 cm soil, while WN decreased aromatic ring condensation and increased the content of nitrogen compound and aliphatic compound. RT increased the functional groups of OH, aliphatic CH2 and nitrogen compound. CT and RD increased the content of C=O and C-O.