Clay Soil - Knowledgebase Question

Portland, OR
Avatar for edchrist
Question by edchrist
December 1, 2000
How do I break up clay soil? I mulch with grass and leaves and they just disappear. My clay is so hard the water just stands on top until it evaporates. Can you give me any suggestions?

Answer from NGA
December 1, 2000
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 inchlayer 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 improvementefforts 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 extension service (ph# 916/842-2711) 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.

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