Structural Analysis of Humic Acid in Soil at Different Corn Straw Returning Modes through Fluorescence Spectroscopy and Infrared Spectroscopy
Table 2
Characteristic peaks of infrared spectra of soil humic acids.
Treatment
Depth (cm)
Relative intensity
Ratio
2920 (cm−1)
2850 (cm−1)
1720 (cm−1)
1620 (cm−1)
1035 (cm−1)
2920/1720
2920/1620
CK
5–20
0.918
0.447
7.550
12.510
1.129
0.181
0.109
St
0.917
0.481
14.608
6.730
2.347
0.096
0.208
Ss
0.835
0.450
14.111
9.510
1.908
0.091
0.135
Smt
0.967
0.341
12.722
9.895
1.531
0.103
0.132
Sms
0.859
0.367
14.364
9.041
2.251
0.085
0.136
CK
20–40
0.772
0.384
12.742
9.176
1.846
0.091
0.126
St
0.970
0.540
14.985
10.360
2.144
0.101
0.146
Ss
1.061
0.509
4.391
16.014
1.633
0.358
0.098
Smt
0.838
0.432
9.524
11.166
1.165
0.133
0.114
Sms
0.804
0.367
14.127
10.269
1.710
0.083
0.114
Note: 2920/1720 means (2920 + 2850)/1720; 2920/1620 means (2920 + 2850)/1620. No straw was applied (CK), straw returning to topsoil (St), straw returning to subsoil (Ss), straw mixing with topsoil (Smt), and straw mixing with subsoil (Sms).
