In two experiments, a central composite response surface design was used to investigate the interactions between herbicide rate (glyphosate in Experiment 1 and metsulfuron in Experiment 2), surfactant rate, and spray application volume on tomato dry weight production. In both experiments, dry weight production was affected by herbicide, and surfactant rate but not spray application volume. Equations derived to predict the response of tomato dry weight production to rates of either, glyphosate

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... metsulfuron, and surfactant explained 89% and 75% of the observed variability respectively. The results suggest that spray application volumes may be decreased without reducing herbicidal efficacy, provided the rates of herbicide and surfactant are maintained constant.