Fig. 1. Principal components analysis (PCA) plot of various pig operation manure chemistry. Values in parentheses indicate the contribution of the first principal component (PC1) or the second principal component (PC2) to the total variation in the chemistry of manure collected from storage tanks. Thus, 86% of the variability in the data could be explained by the type of pig operation. Circles were drawn to facilitate elucidation of the patterns. Pig operations were sow (), finishing (), or mixed (sow, weaner, and finishing) ().