|LABARGE, GREG - The Ohio State University|
|Fausey, Norman - Norm|
Submitted to: Agricultural and Environmental Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/6/2017
Publication Date: 4/27/2017
Publication URL: https://handle.nal.usda.gov/10113/5801831
Citation: Duncan, E.W., King, K.W., Williams, M.R., LaBarge, G., Pease, L.A., Smith, D.R., Fausey, N.R. 2017. Linking soil phosphorus to dissolved phosphorus losses in the Midwest. Agricultural and Environmental Letters. doi: 10.2134/ael2017.02.0004.
Interpretive Summary: Agricultural fields in the Western Lake Erie Basin have been identified as a source of phosphorus (P) contributing to the algal blooms in Lake Erie. Soil test phosphorus (STP) is a measurement that can be used to help identify the risk of P and dissolved reactive phosphorus (DRP) loss in agricultural drainage water. Some fields that have relatively low STP produce P and DRP loads that do not meet recommended thresholds set by the Ohio P Task Force. A combination of STP and other management practices should be used to decrease P and DRP loading.
Technical Abstract: Harmful and nuisance algal blooms resulting from excess phosphorus (P) have placed agriculture in the spotlight of the water quality debate. Sixty-eight site years of P loading data from 36 fields in Ohio were used to see if a soil test P (STP) concentration could be identified that would permit P application while still meeting recommended loss thresholds. Identifying fields with the greatest potential for P risk is required in order to identify helpful P management practices that can reduce P loss and address water quality concerns. Regression analysis revealed that P application to soils with STP concentration in the ‘critical level’ range would result in P losses above the recommended Annex 4 thresholds (spring season loads: 0.11 kg ha-1 dissolved reactive phosphorus (DRP); water year loads: 0.29 kg ha-1 DRP; and concentration thresholds for both spring and water year: 0.05 mg L-1 DRP). In addition, fertilizer application increased the risk of P loss as compared to years in which fertilizer was not applied. Soil test phosphorus provides an initial indicator of fields that are at risk for greater P loss, but STP alone was not a good predictor of P loss, suggesting that a more holistic approach that includes upland management, edge-of-field practices, and in-stream approaches will be required to decrease DRP loading.