An analysis of variance (ANOVA) using SAS 9.1 (SAS Institute Inc., Cary, NC, USA) was conducted to test for differences between (1) treatments (speed and implement) for the measured tractor
performance and soil variables and (2) measured and estimated productivity rate and fuel costs. A least squares regression (LSR) was applied to evaluate linear relationships between fuel
consumption and implement draft along with tractor power and fuel consumption for each implement. SAS was also used to determine if LSR slopes and y-intercepts were statistically different between implements and compute the root mean square error (RMSE) for all regression fits. The estimated and actual fuel consumption and draft data for the John Deere 8300 tractor was analyzed using the same LSR procedure within SAS. All statistical
tests were performed at the 95% confidence interval.