Looking Deeper for Impacts of Soil Management.

For generations soil sampling and analysis has been focused on the A horizon, generally the upper 10 to 20 cm of soil. This is especially true for studies of annual cropping systems in agriculture. For special purposes samples as deep as 30 or 45 cm are sometimes obtained.  We believe that the capacity of soil management and annual cropping systems to influence deeper soil properties has been largely underestimated or ignored.  In recent years our research has attempted to investigate changes taking place 1 to 2 meters deep in agroecosystem profiles. We have found that large pools of N exist below 1meter and that this N can be accessed by cover crops in the fall before winter leaching moves the nutrient out of the profiles and towards streams.  We have also found that cover crops can markedly affect the amount and composition of soil pore water at greater than 1 meter depths, even during the winter season. Likewise, fertilization practices may alter soluble and labile carbon more than 1 meter deep in the profile. Although physically difficult, and subject to even more spacial variability than surface soils,  sampling to greater depth will be important for a complete understanding of soil impacts of agroecosystem management on soil and ecosystem function.