CONCLUSIONS

• Based on extensive soil profile testing, significant vertical stratification of soil phosphorus levels in the upper 20-cm of a profile may result from modern best management practices.
• Because of the observed stratification, bulk sampling (0-15 cm) for agronomic purposes to determine plant nutrient availability does not accurately depict the nutrient levels encountered by growing plant roots.
• Environmental monitoring must reevaluate the current methods as it has been shown that the soil subject to the greatest overland runoff may have higher phosphorus levels than indicated by the bulk sample average.