purchasing a soil mixture from a garden center or landscape supply co
A OSU article in the Feb. 11th Oregonian suggested for clay soils that purchasing a soil mixture from a garden center or landscape supply should be considered. 1. how does one determine which of the "various mixes which meets your specific needs" 2. do you know of any sources for soil or compost that test for levels of pesticides, insecticides, or heavy metals
Washington County Oregon soil and fertility issues
Using imported soil in raised beds allows the gardener to "customize" the mix for the specific items he is growing. For example, if you are growing vegetables you would want a mix with a slightly acid pH (6.5-6.8), a fairly loose textured soil such as sandy loam, and enough added nutrient (composted manures, elemental nutrients to supply nitrogen, phosphorus and potassium), and a sufficient amount of humus forming materials such as shredded bark, leaves, spoiled hay (approximately 30% of the mix.). Flower gardens require similar mixes, with the exception that some flowers prefer more alkaline mixes. You can get information on what is needed for various plant types from a general reference book such as Sunset's Western Garden Book. There are also many pamphlets addressing soil needs of plants on the OSU Extensionwebsite,www. extension.oregonstate.edu. Since I am not familiar with the article you read, I do not know in what context the recommendation was made. I would assume it was referring to using raised beds with imported soil because clay is unsuitable for that purpose. You can of course, add massive amounts of humus forming materials to clay soil, but it takes a long time for good results. As for the second part of your question, you should ask the supplier how he determines the quality of the mix he offers--direct knowledge, "intuition", or testing. If you are concerned about pesticide residues, etc. you might prefer to deal with suppliers of organic mixes, of which there are several in the Rogue Valley. Just share your concerns when you inquire and judge for yourself if your questions are answered to your satisfaction.