The impact of conservation tillage intensities on mean yields and yield risk

Understanding the productivity and production risk effects of conservation tillage practices are important so that growers can make better decisions about tillage systems appropriate for their farm operations. This study investigates the mean yield and yield risk effects of conservation tillage practices with varying levels of tillage intensity and timing. Long-term field trial data for corn (Zea mays, L.) and soybeans (Glycine max, L. Merr.) in the North Carolina Piedmont, together with moment-based regression models, were used to achieve the objective of the study. Our empirical analysis suggests that conservation tillage treatments (with lower tillage intensities and higher residue levels) consistently have higher mean yields than conventional tillage practices in the sandy loam soils of the North Carolina Piedmont. However, we find that conservation tillage practices with lower intensities (and higher residue levels) do not generally have a consistent statistically significant risk reducing effect based on the higher-order moments of the yield distribution (e.g., variance, skewness, and kurtosis). This indicates that conservation tillage does not consistently result in statistically lower production risk relative to conventional tillage methods.