Project: MLMMI 03-01-04
To quantify the benefit of vegetated buffer strips (natural riparian zones and managed buffer strips) in reduction of phosphorus runoff from fields to streams in Manitoba settings.
KEYWORDS: phosphorus, nutrient, vegetated buffer strip, particulate, soluble, riparian, runoff, retention
Funding Partners: who have contributed to MLMMI in support of this project:
MRAC - $33,178
Manitoba Pork Council and industry groups - $33,178
Amount Funded: $66,356.00
Performer Funded: $0.00
Total Cost: $66,356.00
First Progress Report received on February 24, 2004.
Second Progress Report was received on September 2, 2004.
Revised report received on September 30, 2004.
Third Progress Report due on March 1, 2005.
Extension granted until March 30, 2005.
Third Progress Report received on March 23, 2005.
Final Report due on September 1, 2005.
Final Report received on September 12, 2005.
Project results showed that vegetated buffer strips do have the potential to retain P from runoff; however their effectiveness is limited by many factors.
Paired samples of runoff, taken at the field edge and in the vegetated buffer strip, indicated that in about 50 per cent of the cases sampled, the P concentration in the runoff decreased about 30 per cent as the flow passed through the vegetated buffer strips. Runoff flow is highly focused so that only very small portions of a vegetated buffer strip that is of uniform width along a field edge actually intercepts runoff. Vegetated swales that extend into the field would be more effective than a uniform width of vegetated buffer strip along a field edge. The effectiveness of a vegetated buffer strip inevitably varies with time. Vegetated buffer strips function to retain P both while under snow in the melt runoff, and later when there is active growth. However, mechanisms involved and the relative effectiveness will vary with season. Removal of vegetation seems the only effective management practice to remove P from vegetated buffer strips. Observations were that only a small portion of vegetated buffer strips actually intercept runoff flow. Soil analysis indicated that the vegetated buffer strips do retain P, and may actually have higher concentrations of available P than the field soil because of the enrichment processes of erosion and runoff. Soil at eight to 10 cm depth in the vegetated buffer strips had elevated P concentrations, indicating that P is penetrating the vegetative buffer strips, perhaps by infiltration of runoff water or by plant.
Project results were published in the Nov 2006 issue of the Canadian Journal of Soil Science and are available upon request.