Soil Amendments - Knowledgebase Question

Seattle, WA
Question by leesat
December 30, 1998
Last year I created a raised bed on my concrete deck and planned a cutting garden which turned out to be quite successful. I want to do it again this year. What do I need to do to my soil to make sure that my plants have enough nutrients? The soil I filled the bed with last year was potting soil bought in large quantity. I don't want to have to purchase all new soil. Any suggestions?

Answer from NGA
December 30, 1998


Depending upon manufacturer, commercial potting soil is a mixture of sand, peat, leaf mold and vermiculite or perlite. To keep the organic content high, you can add aged compost or leaf mold to the soil mixture at the beginning of each planting season. Spread 3-4 inches of organic matter over the top of the bed and mix it into your soil. Then plant as usual. Instead of purchasing additional potting soil, here are two recipes for homemade soiless mix: Cornell Mix: one-half cubic yard of sphagnum peat moss, mixed together with one-half cubic yard of vermiculite. Then add 5 pounds of dolomitic limestone, 1 pound of superphosphate and 2 pounds of 5-10-5 fertilizer. Mix together thoroughly. The second recipe is called Organic Mix: 16 quarts of sphagnum peat moss, 16 quarts of vermiculite, 7 ounces of bone meal, 3 ounces dried blood meal and 3 ounces of ground limestone. Mix together thoroughly.

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