VARIABILITY OF MECHANICAL IMPEDANCE IN A TILLED ONE HECTARE FIELD OF NORFOLK SANDY LOAM

The spatial variability of field-measured values of mechanical impedance makes it difficult to detect significant differences in impedance effected by different management and/or tillage practices. This study was conducted to examine sources of cone index (CI) variation and to develop models to predict Ci in a 1ha field of Norfolk sandy loam for 3 different tillage practices. The best predictive model for each tillage treatment was selected based upon the correlation coefficient, coefficient of variation, standard deviation, and the normality of the residuals as tested by the Kolmogorov-Smirov statistic. Using these statistics, it was determined that the CI data must undergo a log transformation prior to model development. As much as 40% of the observed spatial variability for treatment N was explained by the full model.-from Authors