Core Diameter Relationship with Nutrient Flux Measurements.

The diameter of soil cores may influence measurement of nutrient flux rates.  Soil cores of various diameters were collected from the St. Johns River floodplain and subjected to flooding to a floodwater depth of 20 cm.  Release rates of dissolved organic matter and nutrients were calculated as the slope of the regression of floodwater nutrient concentrations versus time ranging from 0 to 12 days.  There was no significant difference in release rates of NH4 due to core diameter, with an average NH4 flux of 9.7 mg N/m2/d.  Similarly, SRP flux was unaffected by core diameter and averaged 1.7 mg P/m2/d.  There was no discernable trend in DOC flux with changes in core diameter.  Dissolved organic C flux from 5 cm cores was significantly lower than cores with diameters ranging from 10-20 cm, but not 25 cm.   Total N was also not significantly affected by core diameter, and the TN release rate was about 3.6 times that of NH4.  Likewise, total P was not significantly influenced by core diameter, with the average release rate being 9.0 mg P/m2/yr, approximately 5 times higher than the flux rate of SRP. There was no discernable relationship between either EC and pH as a function of core diameter.  Generally, soils from different core diameters were similar in terms of nutrient and organic matter content.  Nutrient flux, with potential exception of DOC, were generally unaffected by soil core diameter.