WHETHER YOU'RE USING YOUR OWN LOCAL SOIL or importing soil to fill raised beds, soil amendments are a vital resource for ensuring a productive vegetable garden. Many neglected urban soils are compacted and low in organic matter. Soil amendments are designed to add organic material back into soil, reduce compaction, and improve soil life. All that helps increase the yield. Here are some tips from the Soil Science Society of America.
Compost is organic material that has decomposed into a stable state that’s then available for adding to soil. Anything that was once alive can be composted; therefore different composts can vary in their properties. Some of the most common composts available to urban residents are made from the yard debris that is collected curb-side from residents.
Manure can give your garden an incredible boost in nutrients. Make sure the manure you use has been well aged or composted. Check with local agriculture organizations to see if they have a list of local farms willing to share their manure.
Biosolids are the digested, solid portion extracted from the wastewater treatment process. They may not sound pretty—but there’s nothing better for creating an amazing garden. In addition to being 100% recycled and full of macro- and micro-nutrients, biosolids work to build healthy soil like nothing else.
Biosolids are also held to stringent standards by the EPA and have been repeatedly shown to be a safe, effective way to build healthy soil. A small but growing number of cities, however, are investing in the technology to produce Class A biosolids—clean enough to distribute to those gardening in urban areas. A good example of this is Tagro, available in the Pacific Northwest.
You can add amendments to soil anytime, but the best times for working them into an existing garden are in the spring before planting, and in the fall. Generally, two to three inches is sufficient to work into the soil gently with a shovel.
For more information on soil amendments, visit soils.org/discover-soils/soils-in-the-city. Topics under Soils in the City include Community Gardens, Green Infrastructure, Green Roofs, and Soil Contaminants. The Soil Science Society of America also has an informational soils blog called Soils Matter, http://soilsmatter.wordpress.com/.