Deriving the Shannon Index from the soil molecular Humeome serves as a descriptor of soil organic matter stability under different cropping systems

Chemical and Biological Technologies in Agriculture

Table 2 Shannon index (SH), SH multiplied by the % OC in the specific molecular class, and their respective total values (SH_tot) for all the molecular classes, derived from the molecular soil humeome for Control, MIX and Maize of the long-term experiment

Molecular classes^a	CONTROL^b		MIX^b		MAIZE^b
Molecular classes^a	SH	SH × % OC	SH	SH × % OC	SH	SH × % OC
AA/AM/IM	0.910 ± 0.129	0.141 ± 0.020	1.167 ± 0.267	0.144 ± 0.033	1.055 ± 0.019	0.221 ± 0.004
AD	1.380 ± 0.197	0.098 ± 0.014	2.040 ± 0.463	0.172 ± 0.039	2.635 ± 0.052	0.202 ± 0.004
BA/BE/HO/PAH	1.449 ± 0.193	0.030 ± 0.004	1.608 ± 0.342	0.080 ± 0.017	1.361 ± 0.034	0.080 ± 0.002
PA/PE/PH	1.783 ± 0.248	0.115 ± 0.016	2.307 ± 0.528	0.131 ± 0.030	2.422 ± 0.030	0.164 ± 0.002
FA/DA/HA	2.098 ± 0.298	0.345 ± 0.049	2.206 ± 0.493	0.273 ± 0.061	2.156 ± 0.036	0.238 ± 0.004
ES/ET/KE/AC/AH/AL	1.044 ± 0.148	0.212 ± 0.030	1.301 ± 0.295	0.194 ± 0.044	1.161 ± 0.020	0.118 ± 0.002
RA/SE/ST	0.404 ± 0.050	0.032 ± 0.004	0.086 ± 0.014	0.006 ± 0.001	0.129 ± 0.022	0.006 ± 0.001
SA/SET/SU	1.136 ± 0.156	0.153 ± 0.021	0.975 ± 0.756	0.098 ± 0.076	1.224 ± 0.028	0.043 ± 0.001
HN	1.861 ± 0.265	0.197 ± 0.028	1.822 ± 0.410	0.444 ± 0.100	2.165 ± 0.037	0.642 ± 0.011
SH_tot	12.064 ± 1.696	1.323 ± 0.186	13.512 ± 3.512	1.543 ± 0.401	14.308 ± 0.259	1.714 ± 0.031
nCPR	0.680 ± 0.021		0.412 ± 0.038		0.187 ± 0.012
SOMR	0.514 ± 0.084		0.267 ± 0.094		0.109 ± 0.005

The SH and the SH x %OC values were used to calculate the nCPR and SOMR ratios, as described in “Methods” section. Standard deviation was derived by analysis in triplicates
^aAA = amino acids; AM = amines; IM = imines; AD = amides; BA = benzoic acids; BE = benzoic esters; HO = heterocyclic oxygen compounds; PAH = polycyclic aromatic hydrocarbons; PA = phenolic acids; PE = phenolic esters; PH = phenols; FA = fatty acids; DA = dicarboxylic acids; HA = hydroxy acids; ES = aliphatic esters; ET = ethers; KE = ketones; AC = alcohols; AH = aldehydes; AL = alkanes/alkenes/alkynes; RA = resin acids; SE = steroids; ST = sterols; SA = sugar acids; SET = sugar esters; SU = sugars; HN = heterocyclic nitrogen compounds
^bBased on the Humeomics fractionation presented by Savarese et al. (2021) in [29]