Effectiveness of grass filters in reducing phosphorus and sediment runoff

Ahmed Alwadaey, Charles Wortmann, Thomas Franti, Charles Shapiro and Dean Eisenhauer; University of Nebraska

Perennial grass filter strips can remove sediment and nutrients from surface runoff by increasing deposition because of filtration and reduced runoff velocity and by increased infiltration. Well-placed filters can effectively reduce manure phosphorus (P) runoff.

Field research was conducted in 2006 to the spring of 2008 in Nebraska at a site with extremely high soil test P in the surface soil. Fescue grass filters were established around the plot outlets with the filters occupying either 1.1 or 4.3 percent of the plot area. Plot size was 0.01 acre. Twelve runoff events occurred.

Sediment and P losses were greatly reduced by the grass filters, primarily because of increased infiltration and reduced volume of runoff. The effect of the narrow and wide filters, respectively, was to reduce runoff volume by 54 and 79 percent, sediment loss by 67 and 84 percent, total P loss by 68 and 76 percent, particulate P loss by 66 and 82 percent and dissolved P loss by 73 and 66 percent.

A snowmelt runoff event had 56 percent greater concentration of dissolved P compared with rainfall-induced runoff events. Well-placed perennial grass filters occupying 1.1 percent of the drainage area greatly reduced sediment and P loss to surface waters when they effectively reduce runoff. ANM

—Excerpts from Animal Manure Management Monthly, December 2008