Sarah Butler

"Nutrient cycling in freshwater wetland soils and their relationship to surface water nitrogen and phosphorus."
BSES Senior Research 2003

Surface water inorganic nitrogen (N) and phosphorus (P), bioavailable soil N and P, and total soil N and P were measured in ten freshwater wetlands of Indiana to determine relationships between soil N and P and wetland nutrient condition.

Soil extractable PO4-P (weight basis) was positively related to surface water NH4-N (R2 = 0.57; p < 0.01) and PO4-P (R2 = 0.63; p <0.006). Extractable P (volume basis) also was positively related to surface water NH4-N (R2 = 0.61; p < 0.008). Extractable NH4-N was unrelated to surface water N and P, but was positively related to total soil organic N (R2 = 0.69; p < 0.006). There was no significant relationship between total P and N and surface water nutrients.

Plant available P may be a reliable indicator of nutrient enrichment in freshwater wetlands in Northeast Indiana. Bioavailable N is not a good indicator of nutrient condition because it is controlled by the amount of soil organic matter and total nitrogen rather than by nutrient loadings. Total N and P are also unreliable indicators of freshwater wetland nutrient enrichment. Plant available P needs to be tested in other ecoregions and geographic areas to gauge its effectiveness as an indicator of wetland nutrient condition across a wide range of environmental conditions and wetland types.