Are Legacy Phosphorus Estimates Predictive of in situ Soil Phosphorus Concentrations?
Abstract
The buildup of phosphorus (P) in soils, sometimes referred to as legacy P, can intensify hydrologic losses that may contribute to downstream ecological degradation. National nutrient inventories provide one estimate of legacy P, but the relationship between these inventory-based estimates and actual soil P concentrations remains unclear. In this study, we assessed relationships between national legacy P data reported in the NuGIS dataset and lab-measured soil test phosphorus (STP, estimating the portion of phosphorus that is bioavailable to plants) and total phosphorus (TP, representing all phosphorus, labile or non-labile, in soils). While TP data (from USGS) were available at discrete locations throughout the US, STP data were only available at the county-scale for North Carolina, Ohio, and Arkansas. Total historical legacy P was summed from 1987 (the earliest year in the NuGIS dataset) to the year before in situ STP or TP values were measured. Analyses comparing STP and TP with total historical legacy P revealed that legacy P was positively correlated with STP for the three study states based on Pearson correlation coefficients (NC: r = 0.56, AR: r = 0.49, OH: r = 0.75); correlations between legacy P and surface TP (top 5 cm) yielded smaller r values (NC: r = 0.11, AR:.r = -0.06, OH: r = 0.31). Alternate starting years of legacy P aggregation also affected the correlation relationship. For STP, a smaller aggregation period (e.g., starting from 2010 instead of 1987) resulted in substantially lower correlations for NC and OH, highlighting the need for long-term records of legacy P. These results suggest that legacy P is an important driver of the P available for plant uptake (STP). On the other hand, factors like existing geogenic concentration and weathering processes could confound the relationship between legacy P and TP. Consistent with this hypothesis, legacy P is found to be somewhat more strongly correlated with the difference in TP concentration between the surface and the underlying soil parent material. Future research will continue to refine relationships between legacy P estimates and soil P concentrations across the United States.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFMGC12C..05T