How to break up heavy grey clay in soil - Knowledgebase Question

Eagle, ID
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Question by tinacrs3
June 25, 2007
I live in Idaho on a large

Answer from NGA
June 25, 2007
Clay soil can be a real gardener's nightmare! You can begin, on a small scale, to improve the soil by working in lots of compost or other organic matter. Choose flower or vegetable beds that you want to plant this year and spread a three or four inch layer of mulch on top. Work it in to a depth of at least six inches, deeper if you can. Continue to do this year after year to help "fluff" up the soil. If you start small, in beds you plan to use immediately, you can spread your soil improvement efforts throughout the yard over several growing season. Persistence will pay off and eventually you'll have a loamy-type soil that will drain well yet hold important nutrients and moisture. Adding Gypsum may help break up the clay.

Your cooperative extension service can give you soil testing information, and can tell you if gypsum will improve your soil - it won't work for some clay soils. If all of this sounds like too much work, you can always garden in raised beds on top of your tough soil! Here's how: Loosen and turn the native soil under the planting area, then use lots of organic matter (compost, rotted leaves, aged stable manure and bedding, etc.) and a bit of sand to increase the volume. Mix them together as best you can and plant into that. For annuals, a six inch height should be ample, for perennials you might want to go a bit higher. Over time, you will find that the soil in these areas is much improved, particularly if you add additional organic matter regularly. Using an organic mulch such as shredded bark will also help to feed the soil as it breaks down. If you are still unsure, plant annuals this year and then add lots of organic matter again this fall in preparation for planting perennials next year. This will also give you time to run some soil tests and see what if any additional amendments you may need to add.

Coffee grounds are a good source of nitrogen and are only slightly acidic. If you want to plant hydrangeas and azaleas, you can add peatmoss to the soil prior to planting and then feed them with an acidified fertilizer (one formulated especially for azaleas).

Best wishes with your new landscape!

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