Influence of pasture stocking method on surface runoff and nutrient loss in the US Upper Midwest

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

Submitted to: Nitrogen
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2023
Publication Date: 11/16/2023
Citation: Young, E.O., Sherman, J.F., Bembeneck, B., Jackson, R.D., Cavadini, J., Akins, M.S. 2023. Influence of pasture stocking method on surface runoff and nutrient loss in the US Upper Midwest. Nitrogen. 4(4):350-368. https://doi.org/10.3390/nitrogen4040025.
DOI: https://doi.org/10.3390/nitrogen4040025

Interpretive Summary: Hay production and grazing livestock are two common dairy farm management practices. In rotation with corn silage, hay and pasture can dramatically reduce soil erosion and particulate nutrient loss in surface runoff. However, few studies have compared sediment and nutrient loss directly between hay and pasture systems. A study was conducted at the Marshfield Agricultural Research Station to evaluate runoff water quality and nutrient loss in a typical Upper Midwest hay crop production field receiving liquid dairy manure in comparison to pasturing and grazing dairy heifers. Fields were managed as hay with two to three harvests per year and applications of liquid dairy manure during the calibration phase (2013-2018). Grazing treatments started in 2018 (the control field remained in hay) and included: i) continuous stocking (CS; animals had unrestricted pasture access), ii) primary paddock stocking (PPS; limited access with rotation) iii) adaptive multi-paddock stocking (AMPS; limited access with rotation). Sediment, nitrogen (N) and phosphorus (P) concentrations were monitored year-round in surface runoff. Results indicate that grazing increased average runoff compared to the hay field and tended to decrease nutrient concentrations but increased loads (due to higher runoff). The CS system had greater average surface runoff and larger N and P loads compared to the control. Forage availability was lowest for CS, suggesting neither animal productivity nor runoff water quality were optimized. AMPS had lower total N and P loss in runoff as a percentage of applied manure N and P (1.3 and 1.6%) compared to the control (2.5 and 2.1%), PPS (2.5 and 2.6%), and CS (3.2 and 3.0%). Our results show that stocking method strongly impacted edge-of-field surface runoff water quality and nutrient use efficiency of the grazing systems and highlight the need for water quality models to account for pasture management.

Technical Abstract: Hay production and grazing livestock can reduce erosion compared to annual crops, however few studies have directly compared these systems. We evaluated runoff water quality and nutrient loss between a hay field and dairy heifer grazing management systems using a paired watershed design. Four edge-of-field sites at a research farm in central Wisconsin were managed as hay during calibration (2013-2018) followed by a grazing phase (2018-2020) with three treatments (continuous stocking, CS; animals had unrestricted pasture access, ii) primary paddock stocking, PPS; limited access with rotation, or iii) adaptive multi-paddock stocking, AMPS; limited access with rotation). Runoff, sediment, nitrogen (N) and phosphorus (P) loads were monitored year-round. Grazing increased average runoff volume by as much as 1.7-fold and tended to decrease N and P concentrations but increased loads. CS had larger mean sediment (2.0-fold), total N (1.9-fold) and total P loads (1.2-fold) compared to the control and lower forage availability, suggesting neither animal productivity nor water quality were optimized. AMPS had lower N and P loss as a percentage of applied manure N and P (1.3 and 1.6%) compared to the control (2.5 and 2.1%), PPS (2.5 and 2.6%), and CS (3.2 and 3.0%). Stocking method had a marked impact on nutrient loss in surface runoff from these systems, suggesting water quality models should account for pasture management.