Often, the major source of "damage" from inadequate drainage relates to timeliness of field operations. Inadequate drainage can delay spring field operations from days to a week or more. Occasional wet spots also interrupt field traffic patterns and cause field operations to be less uniform. Vehicle traffic on soils that are too wet will cause increased soil compaction. Delays in planting mean a shorter growing season for the crop. Once the crop is planted, inadequate drainage can cause stunted and shallow root growth, and sometimes, complete crop failure due to excess-water stress (lack of oxygen in root zone). Planting delay, soil compaction, and excess-water stress, combined, can translate into significant crop yield impacts. The magnitude of the yield impact for a growing season depends on crop and variety, soils, and the season's rainfall pattern.