Spatial variation in soil water and nitrogen are often the causes of crop yield spatial variability due to their influence on the uniformity of plant stand at emergence and for in-season stresses. Natural and acquired variability in production capacity or potential within a field causes uniform agronomic management practices for the field to be correct in some parts and inappropriate in others. To achieve the ultimate goal of sustainable cropping systems, variability must be considered both in space and time because the factors influencing crop yield have different spatial and temporal behavior. Determining the optimum prescription for a location within a field is challenging. The biggest challenge is that the plant response to variable management levels is often highly dependent upon the weather that occurs during the season. The objective of this study was to quantify the causes of yield variabilility in a 5 year study carried out in Southern Italy.  Remote sensing imagery, field measurements on soil and crop variables, Electrical Resistivity Imaging were taken during the five growing seasons. A system approach was used to assess the long term impact of weather on previously identified management zones.  The system approach was able to explain the causes of yield variability over space and time.