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Long‐term Variation in Agricultural Edge‐of‐Field Phosphorus Transport during Snowmelt, Rain, and Mixed Runoff Events
Author(s) -
Hoffman A. R.,
Polebitski A. S.,
Penn M. R.,
Busch D. L.
Publication year - 2019
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2018.11.0420
Subject(s) - surface runoff , snowmelt , environmental science , hydrology (agriculture) , nonpoint source pollution , spatial variability , water quality , erosion , sediment , ecology , geology , paleontology , statistics , geotechnical engineering , mathematics , biology
Runoff of nutrients and erosion of soil from agricultural lands affect soil fertility and are important nonpoint contributors of P and N to surface and ground waters, yet studies of edge‐of‐field nutrient transport from snowmelt or rainfall runoff on frozen ground are limited. The objective of this study was to quantify the temporal and spatial variation in edge‐of‐field snowmelt, rain, and mixed (rain on snow) runoff events for sediment and P loadings in five agricultural subwatersheds over a 12‐yr period. Edge‐of‐field runoff events from five subwatersheds at Pioneer Farm near Platteville, WI, ranging in size from approximately 4 to 30 ha were sampled using automated samplers from 2002 through 2014 to determine sediment and P yields (mass loads). Mean dissolved reactive P (DRP) runoff concentrations for each event type (rain = 1.24 mg L −1 , snow = 1.90 mg L −1 , mix = 2.23 mg L −1 ) were above total P (TP) water quality guidelines for surface waters. The percentages of TP that was DRP for snow, mixed, and rain events were 74, 84, and 39%, respectively. Although variation in total annual P yield in edge‐of‐field runoff was noted between years and among sites within a given year, when aggregated over the study period, the subwatersheds showed similar transport characteristics with respect to DRP and TP yield. This study highlights the importance of examining long‐term datasets in quantifying annual yields and understanding the timing of DRP and TP transport for developing best management practices and improving model accuracy in cold weather agricultural systems. Core Ideas Runoff events were monitored in five agricultural subwatersheds over 12 yr. Edge‐of‐field total P yield and P transport timing showed interannual variability. P yields during events were not significantly different among sites. Snowmelt and mixed precipitation runoff mobilized a higher proportion of soluble P. Conditions during spring thaw affect rain‐driven P yields in subsequent months.