Carbon to Nitrogen Ratio
Nitrogen in water can contribute to eutrophication, or nutrient-enrichment, in saltwater systems. It may also contaminate groundwater, causing an illness harmful to infants called blue baby syndrome.
Nitrogen loss from bioswales can be managed by using soils with an appropriate carbon to nitrogen (C:N) ratio. The exact ratio will depend on the nitrogen demands of the plants, but a suggested value is 35:1. Adding wood chips to soil can increase the amount of carbon. A wood mulch layer can also help immobilize nitrogen while reducing weed growth and retaining moisture in the soil.