Table 4.

Coefficients for determinants of drift from AFA, DAT, and MFT spray trials.^a

Fixed effectsb	Model estimate (95% CI)	SE	P-value
Intercept	4.21 (3.65, 4.76)	0.29	<0.001
DAT sprayer	−0.07 (−0.19, 0.06)	0.06	0.29
MFT sprayer	−0.35 (−0.49, −0.22)	0.07	<0.001
Distance (m)	−0.06 (−0.07, −0.05)	0.01	<0.001
Height (m)	0.13 (0.10, 0.16)	0.02	<0.001
Wind speed (m s−1)	0.28 (0.16, 0.40)	0.06	<0.001
Variance componentsc	Random and fixed effects included	Only random effect included
Within-location (residual)	0.498 (79.5%)	0.581 (30.4%)
Between-location (intercept)	0.128 (20.5%)	1.328 (69.6%)
Total variance	0.626 (100%)	1.909 (100%)

^aThere were 669 tracer-based drift volume levels (ln-µl) measured on PE lines at fifteen downwind locations in fifteen AFA, DAT, and MFT spray trials.

^bAFA sprayer was the reference level for the ‘sprayer’ term in the model. Fixed effect estimates for DAT and MFT sprayers indicate drift-reducing performance compared to the AFA sprayer reference (i.e. larger negative values show greater drift reduction potential).

^cWhen the fixed effects were dropped from the model, within-location variance was 0.581 (30.4%) and between-location variance was 1.328 (69.6%). Fixed effects impacted the between-location component of the variance (1.328–0.128, 90% reduction) considerably, but did not alter the within-location component of variance (0.581–0.498, 14% reduction) as much. The difference between these models suggests that there were relatively few systematic changes for individual locations across spray trials.