Compost Mulch - Knowledgebase Question

Name: Arlene adamson
Bakersfield, CA
Avatar for leinieadamso
Question by leinieadamso
December 6, 1999
I have hard clay soil. My husband tried adding gypsum to the soil, but it didn't seem to make a difference in the texture. He doesn't want to spend more money adding more if it isn't going to work. He has only added the gypsium one time. This weekend I have hired someone to come in an add approximately a 3" layer of compost to lay on top of our flower beds. It is coming from a gardening recyling center. The mixture is supposed to be brown material, leaves and grass. The person who mows my yard says that it is very rich looking. Should I add other amendments to the compost dirt? This is the first time that any compost has been added to the soil. Over the years, we have had redwood chip mulch which of course has broken down. These chips have been added at two different times in the last 10 years. Before this, the ground was open field. The soil was very compacted. If we want to plant a deep plant, we have to use a crow bar to break it up. What I am concerned about is can I smother my plants, by adding the compost dirt? Thank you.

Answer from NGA
December 6, 1999
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 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.

It is possible to dicourage the growth of some plants by piling too much soil or mulch over the crowns. Peonies, for instance, won't grow well or blossom if their roots are deeper than a couple of inches in the ground. Others might rot if they don't have access to air. The best solution is to use the compost as mulch around your established plants rather than over the top of them.

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 containers on top of your tough soil!
Good luck!

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