https://doi.org/10.2134/jeq2017.06.0234

Plach, J. M., Macrae, M. L., Ali, G. A., Brunke, R. R., English, M. C., Ferguson, G., Lam, W.V., Lozier, T.M., McKague, K., O'Halloran, I.P., & Opolko, G. (2018). Supply and transport limitations on phosphorus losses from agricultural fields in the lower Great Lakes region, Canada. Journal of environmental quality, 47(1), 96-105. https://doi.org/10.2134/jeq2017.06.0234

Phosphorus (P) mobilization in agricultural landscapes is regulated by both hydrologic (transport) and biogeochemical (supply) processes interacting within soils; however, the dominance of these controls can vary spatially and temporally. In this study, we analyzed a 5-yr dataset of stormflow events across nine agricultural fields in the lower Great Lakes region of Ontario, Canada, to determine if edge-of-field surface runoff and tile drainage losses (total and dissolved reactive P) were limited by transport mechanisms or P supply. Field sites ranged from clay loam, silt loam, to sandy loam textures. Findings indicate that biogeochemical processes (P supply) were more important for tile drain P loading patterns (i.e., variable flow-weighted mean concentrations ([Cf]) across a range of flow regimes) relative to surface runoff, which trended toward a more chemostatic or transport-limited response. At two sites with the same soil texture, higher tile [Cf] and greater transport limitations were apparent at the site with higher soil available P (STP); however, STP did not significantly correlate with tile [Cf] or P loading patterns across the nine sites. This may reflect that the fields were all within a narrow STP range and were not elevated in STP concentrations (Olsen-P, ≤25 mg kg−1). For the study sites where STP was maintained at reasonable concentrations, hydrology was less of a driving factor for tile P loadings, and thus management strategies that limit P supply may be an effective way to reduce P losses from fields (e.g., timing of fertilizer application).

https://doi.org/10.2134/jeq2017.06.0234