ESTCP Project #1011, Rhizosphere
each dependent variable grouped by TPH and summed PAHs, aliphatic fractions, and aromatic
fractions are shown in Figures 21 through 23, respectively.
4.3.4 Results for One-Way ANOVA Comparison of Plot Treatments. Using one-
way ANOVA, we observed no significant effects for any of the dependent variables listed above.
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.