Fig. 2.

Spreads of the observations with effects of a organic fertilizers (Organic), b mineral balanced NPK fertilizers (Mineral), c combination of organic and mineral fertilizers (Mixed), and d total of all three fertilizers (Total) on alkyl, O-alkyl, aromatic, and carbonyl C groups, and the ratio of alkyl to O-alkyl groups (A/O), and the ratio of alkyl to aromatic groups (A/Aroma) in soil samples calculated from the 277 pairwise data collected 10 studies worldwide. No-fertilization of each study is considered the control (i.e., 1.0). The value shown in the box indicates median, the cross mark indicates mean, and lower and upper quartiles per management