|BUSCH, DENNIS - University Of Wisconsin|
|GOOD, LAURA - University Of Wisconsin|
Submitted to: Agricultural Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/2015
Publication Date: 9/14/2015
Publication URL: http://handle.nal.usda.gov/10113/5422002
Citation: Vadas, P.A., Powell, J.M., Brink, G.E., Busch, D.L., Good, L.W. 2015. Whole-farm phosphorus loss from grazing-based dairy farms. Agricultural Systems. 140:40-47.
Interpretive Summary: Phosphorus (P) loss from agricultural farms is a major water quality issue. For dairy farms, P can be lost from cropland, pastures, and open-air lots. We need to estimate P loss from all these areas to identify the ones that most need better management. We surveyed four grazing-based dairy farms in Wisconsin, USA and used computer models to estimate P loss from all areas on the farms. At the whole-farm level, annual P loss was low generally because a lot of land was in well vegetated pastures or hay and had low erosion. Some farm areas did have high P loss. For cropland, the most P loss was from areas with exposed soil, typically for corn production, and especially on steeper sloping land. The farm areas with the greatest P loss were often animal lots, such as barnyards, and over-wintering areas. Our project shows how fairly simple producer surveys and relatively user-friendly models like RUSLE2, Snap-Plus, and APLE can rapidly and reliably estimate P loss from all areas on a dairy farm and identify areas that need different management in order to reduce P loss from farms.
Technical Abstract: Phosphorus (P) loss from agricultural farms persists as a water quality impairment issue. For dairy farms, P can be lost from cropland, pastures, and open-air lots. We used interview surveys to document land use, cattle herd characteristics, and manure management for four grazing-based dairy farms in Wisconsin, USA. We then used the SnapPlus and APLE models to estimate annual P loss from all areas on these farms and determine their relative contribution to whole-farm P loss. At the whole-farm level, average annual P loss (kg ha-1) from grazing-based dairy farms was low (0.5 to 1.8 kg ha-1), generally because a significant portion of land was in well vegetated pastures or hay and had low erosion. However, there were areas on the farms that represented sources of significant P loss. For cropland, the greatest P loss was from areas with exposed soil, typically for corn production, and especially on steeper sloping land. The farm areas with the greatest P loss were concentrated animal housing, including barnyards, and over-wintering and young-stock lots. These areas can represent from about 5% to almost 30% of total farm P loss, depending on lot management and P loss from other land uses. Our project builds on research to show that producer surveys can provide reliable management information to assess whole-farm P loss. It also shows that we can use models like RUSLE2, Snap-Plus, and APLE to rapidly, reliably, and quantitatively estimate P loss in runoff from all areas on a dairy farm and identify areas in greatest need of alternative management.