Grazing system impacts on surface runoff water quality compared to a hay crop production field with broadcast manure application

Authors: Young, Eric; Sherman, Jessica; BEMBENECK, BROOKE - Marathon County Conservation, Planning, And Zoning; JACKSON, RANDALL - University Of Wisconsin; CAVADINI, JASON - University Of Wisconsin

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/8/2023
Publication Date: 11/1/2023
Citation: Young, E.O., Sherman, J.F., Bembeneck, B., Jackson, R., Cavadini, J. 2023. Grazing system impacts on surface runoff water quality compared to a hay crop production field with broadcast manure application. ASA-CSSA-SSSA Annual Meeting Abstracts. ASA-CSSA-SSSA Annual Meeting, 29 October 2023 - 1 November 2023, St. Louis, MO.

Interpretive Summary:

Technical Abstract: Cropping systems influence nutrient loss and runoff water quality. Both grazing and hay crop forage production with manure application are common practices for dairy farms, but few studies have compared their effects on surface runoff water quality under similar conditions. We conducted a small-catchment, paired-watershed study to compare runoff water quality of three grazing regimes and harvesting hay with surface applied (broadcast) liquid manure at the Marshfield Agricultural Research Station in Stratford, Wisconsin. During the calibration phase (2012-2018), the four watersheds were managed identically as hay crop forage fields with liquid manure applied after cuttings. For the treatment phase (2018-2020), five dairy heifers were assigned to each of three grazing systems at equivalent stocking rates (800 kg /ha). Grazing systems were continuous (CONT), adaptive multi-paddock (AMP), and permanent paddock grazing (PPG). CONT and PPG systems increased runoff quantity and total dissolved solids compared to the hay crop/broadcast manure system (i.e., the control). Grazing treatments decreased total nitrogen and ammonium-nitrogen concentrations in surface runoff, however CONT and PPG had greater total nitrogen loads than the hay crop control. Rain events had greater runoff nitrogen concentrations than snow events. CONT and PPG had lower total and dissolved reactive phosphorus concentrations for rain events, while AMP had greater concentrations than the control. For snow events, grazing decreased total and dissolved reactive phosphorus concentrations, however CONT significantly increased total nitrogen and phosphorus loads. Overall, results suggest similar surface runoff nutrient losses between the hay crop and grazing systems, with differences related to seasonality and specific hydrologic conditions.