Managing Nutrient Release In Compost-Amended Bioswale Soils
Soils put into the columns were mixed at a base ratio of 40 percent compost to 60 percent silica sand by volume. Targeted PSI levels were achieved before additions of water to mimic two types of storm events.

Research shows adding water treatment residuals to a bioswale soil mix immobilizes nutrients in compost that might otherwise leach.
Katrina Mendrey
BioCycle March 2013, Vol. 54, No. 3, p. 36