Table 1.
Number of the organic and conventional fresh produce samples collected by crops.
Fig 1.
Boxplots of nitrogen (a) and carbon (b) content (%), and C/N ratio (c) of conventional and organic crops.
Bars above boxplots denote a Welch two-sample t-test between conventional and organic crop, with adjusted (***),
(**),
(*), and non-significant otherwise (ns). p-values are Holm corrected by each family defined by tests within the same subfigure.
Table 2.
Isotopic composition of C (δ13C, ‰) and N (δ15N, ‰) by production system and geographic origin. Entries are in the format “mean (sd) letter”. Letter displays show Tukey range test significance for each isotope, among countries (columns). Different letters indicate the group difference of means is significantly different than 0 at the 0.05 level. The p-value column shows a Welch t-test between production systems within each country for each measured variable (rows).
Fig 2.
Stable isotope ratio of δ13C (a and b) and δ15N (c and d) of organic and conventional crops.
Bars above boxplots denote a Welch two-sample t-test between conventional and organic crop, with (***),
(**),
(*), and non-significant otherwise (ns). p-values are Holm corrected by each family defined by subfigure.
Fig 3.
ROC curves based on predicted probabilities of organic classification from GLMM model across dataset.
Population averaged and subject specific models for “company” are both shown. The drop in AUROC between the models show the loss of company information in classification. The tradeoff between true positive rate (TPR) and false positive rate (FPR) is relatively symmetric in the tails. We focus our attention on regions of high TPR for developing crop specific cutoffs for covariates.
Fig 4.
Effect profile plots of (a) δ15N, (b) C/N Ratio, (c) C percentage with crop specific sample averages for other covariates.
Fitted probabilities are population-averaged across company/regions. 95% confidence intervals (normal approximation) are shown for fitted probability of organic classification in dotted lines. Marginal sample distributions of covariates for each crop are shown as ticks across the bottom axis.