Results for One-Way ANOVA

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Probability values are listed in Table 4. In the table, P values < .20 are noted via bold type. Due

to the variable nature of field data, probabilities < 20% are often considered to have practical

significance and we have done so in these analyses. The implication of these findings is that a

one-way ANOVA comparison of treatment effects is reasonably representative of the approach

likely to be used in typical field demonstrations--three to four replications of two to several

treatments. This ESTCP project provides data comparing two levels of two treatments, replicated

four times at each of three locations, and normalized for concentration differences and the

temperature of the locations, and the data did not uncover significant effects P<.05 for any of the

treatments. Using a one-way ANOVA, only one fraction, the aromatic C>10-12, showed a

significant treatment at P=0.146, and this was a reduction in treatment efficacy for the fertilizer

treatment relative to either the control or treatments that included vegetation (Figure 24). Our

data from similar studies conducted at two locations in Korea showed an apparent reduction in

treatment efficacy, relative to both the control and planted treatments, when fertilizer alone was

used (Reynolds et al., 2001). These data suggest that "standard" monitoring approaches for

"typical" treatment durations are unlikely to detect a rhizosphere treatment effect, and suggest

that the greatest effect relative to a control treatment is in specific petroleum fractions.

4.3.5 Results for Two-Way Factorial ANOVA Comparison of Main Effects of

Fertilizer, Plants, and Their Interactions. Table 4 also lists the P values for the main

effects and interactions of the factorial ANOVA, using all depletion data from the three sites,

normalized to decalin and GDD-C. All means and 95% confidence intervals are also shown in

Figures 28-35. Data showed no significant interactions.