|CAVADINI, JASON - University Of Wisconsin|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/24/2020
Publication Date: 12/29/2020
Citation: Sherman, J.F., Young, E.O., Jokela, W.E., Casler, M.D., Cavadini, J. 2020. Influence of best management practices on runoff, sediment, phosphorus, and nitrogen loading in a corn silage system: A paired watershed study. Journal of Environmental Quality. https://doi.org/10.3390/soilsystems5010001.
Interpretive Summary: Sediment and nutrient losses are major concerns on dairy farms for both economic and environmental reasons. Dairy manure is an important source of crop nutrients, but can contribute to water quality degradation in some situations if not properly managed. Fall dairy manure application with or without tillage is a routine practice on many dairy farms. While incorporation of manure reduces ammonia volatilization, as well as runoff losses of soluble phosphorus (P) and nitrogen (N), it can contribute to greater soil erosion and sediment mobilization in runoff due to soil disturbance prior to the non-growing season when runoff potential is elevated. In addition to manure application and tillage timing, including additional best management practices, such as planting cover crops and/or grass buffer strips may further improve runoff water quality. To better understand how differing practices influence runoff water quality in corn silage systems, we conducted a multiyear small paired watershed study at the University of Wisconsin/USDA-ARS Marshfield Agricultural Research Station to determine how the routine practice of fall manure application with chisel tillage (control treatment) compared to three other practices: 1) fall manure application with spring chisel tillage, 2) fall rye cover crop with spring manure/chisel tillage, and 3) fall manure application/chisel tillage with a grass buffer strip. Results showed that fall manure application/chisel tillage resulted in substantially less average dissolved P and ammonium in runoff, however erosion (as measured by runoff water sediment concentrations) and total N/P losses in runoff were greater. Fall manure application with spring tillage increased dissolved P and ammonium in runoff, but significantly decreased sediment and total N/P losses. The buffer strip decreased sediment and total N/P but increased dissolved reactive P in runoff. The rye cover crop with spring manure/tillage significantly reduced both sediment and nutrients while also showing effectiveness during the non-growing season and for snow melt events. More research on the impacts of winter rye after corn silage as a cover crop and/or double crop (harvested as dry hay, silage, or straw) on runoff water quality and overall farm nutrient efficiency is warranted.
Technical Abstract: Best management practices (BMPs) can mitigate agricultural nutrient runoff. We evaluated three BMPs designed to mitigate sediment and nutrient losses from corn silage fields. Four paired watershed fields in central Wisconsin equipped with year-round monitoring were used. After a 2-year calibration period (2006-2008), corn silage production with fall applied manure/chisel tillage, and a 3.5-yr treatment period with BMPs were imposed (2008-2012). Fall applied manure with chisel tillage (FACT) was the control treatment, and the BMPs evaluated were : i) a fall rye cover crop with spring manure application and chisel tillage (FRSACT); ii) fall manure application with spring chisel tillage (FASCT), and iii) fall applied manure with chisel tillage plus a grass buffer strip (FACTB). Year-round runoff monitoring included flow, total phosphorus (TP), dissolved reactive phosphorus (DRP), ammonium, nitrate, total nitrogen (TN), and suspended sediment (SS). Results showed that average runoff for FRSACT and FASCT increased by 131 and 34%, respectively, whereas FACTB was similar to FACT. While FASCT increased mean ammonium, TP and DRP loads by 197, 46 and 376%, respectively, FRSACT significantly mitigated SS, TN, and TP transport. Average DRP concentrations within runoff for BMPs increased by 1.9 to 8.6 times compared to the calibration period. Results suggest that while BMP’s showed mitigation potential for SS, TN and TP, the combination of repeated manure application, reduction in SS and increase in soil labile P appeared to enhance DRP mobilization to runoff, suggesting additional practices may be needed to effectively mitigate DRP loss in manured corn silage fields with high runoff potential.