Journal
JOURNAL OF ENVIRONMENTAL QUALITY
Volume 47, Issue 1, Pages 96-105Publisher
WILEY
DOI: 10.2134/jeq2017.06.0234
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Funding
- Ontario Ministry of Agriculture, Food, and Rural Affairs New Directions
- Agricultural Adaptation Council Farm Innovation Program
- Grain Farmers Association of Ontario
- Lake Simcoe Clean Up Fund (Environment Canada)
- Best Management Practices Verification Program
- Lake Simcoe Clean Up Fund (Ontario Ministry of Agriculture, Food, and Rural Affairs)
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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 ([C-f]) 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 [C-f] and greater transport limitations were apparent at the site with higher soil available P (STP); however, STP did not significantly correlate with tile [C-f] 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).
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