CONSERVATION EFFECTS ASSESSMENT FOR THE ST. JOSEPH RIVER WATERSHED
Location: National Soil Erosion Research Lab
Title: Phosphorus transport from row crop agriculture in the Midwestern U.S.: Problems with scaling up from small plot to watersheds
Submitted to: 5th International Phosphorus Workshop(IPW5)
Publication Type: Proceedings
Publication Acceptance Date: July 1, 2007
Publication Date: September 3, 2007
Citation: Smith, D.R., Pappas, E.A., Livingston, S.J., Flanagan, D.C., Huang, C. 2007. Phosphorus transport from row crop agriculture in the Midwestern U.S.: Problems with scaling up from small plot to watersheds. In: (G.Heckrath, G.H. Rubaek, and B. Kronvang, Eds.) Diffuse Phosphorus Loss: Risk Assessment, Mitigation Options and Ecological Effects in River Basins. Proceedings of the 5th International Phosphorus Workshop(IPW5). Silkeborg, Denmark. pp. 181-814.
Eutrophication is the result of P transport at the catchment scale, while P management occurs at the field to farm scale, and the environmental basis for making nutrient management decisions are often based on plot scale data. The objective of this research was to develop a better understanding of up-scaling of P transport from the plot to catchment. Rainfall simulations occurred on three sizes of plots that were nested within two fields, which were in turn nested within a series of catchments draining approximately 4,300 ha. Plot data typically over-predicted nutrient transport from fields. Given that this research was conducted in a region with intense sub-surface tile drainage, field runoff data does not necessarily predict the P transport to drainage ditches. Closer examination of drainage ditches during storm events indicates that tile inlets can act as point sources. As such, the best way to reduce contaminant transport from agricultural fields might be to locate tile inlets with high sediment or P loads, and focus conservation efforts at the problematic tile inlets. While modeling efforts will assist, ground-truthed data is essential to identifying the potential sources of P, and the sites where conservation efforts have the greatest likelihood of success.