Click on image to view larger version.
Fig. 2. Mean percentage of relative enrichment of soil organic C (SOC), total N (TN), particulate organic matter (POM)-C, POM-N, and Illinois Soil N Test-N (IL-N) fractions in surface soils (generally 0 to 25 cm) of organic farming systems relative to conventional farming systems at nine long-term farming systems trials in the USA. The percentage of relative enrichment calculations were made on paired sets of soil organic matter fraction concentrations (g kg–1 or mg kg–1) in conventional and organic systems within sites. Different lowercase letters indicate significant differences among fractions at the p < 0.05 level. Statistical analysis was conducted on transformed data [(enrichment + 200)–1] to improve normality and equality of variance; untransformed means are presented in the figure.
