Newly Registered
Posts: 1
Joined: Mon Jun 15, 2015 10:46 am

Heavy Clay Soil Amendment

I am new to gardening and have been doing some research on soil amendment. I have heavy clay soil and was wondering if I could begin by tilling my soil and putting an excess of coffee grounds and horse manure as these are available to me for free. I have begun a compost pile but the quantity won't be near enough to amend the area I would like. I am working an area 10 x 50 ft and am currently getting by with container gardening and will continue to do so until my plot is ready ( a few years from what I understand). I have very alkaline soil and from what I have read, coffee grounds make soil acid and also easier to work. I have also read that this will attract red wigglers that will also help with working my soil (I have also begun vermicomposting :D ). All of which I am in dire need of. I just read a post from Michael C who planted a winter cover crop. He too has heavy clay and his garden looks great!! I may do the same. I appreciate any input. Thanks,CC.

User avatar
Super Green Thumb
Posts: 25279
Joined: Sun Feb 15, 2009 6:04 pm
Location: TN/GA 7b

Re: Heavy Clay Soil Amendment

You are basically right that it will take a few years of working on it, before it approaches really good garden soil. That doesn't mean you can't plant anything in the meantime. It means what you plant won't thrive as well and you are more limited in what you can plant (carrots for example are OUT).

(Used) Coffee grounds are a good addition to your soil, but it is a myth that it will acidify it. Most of the acidity goes in to the coffee when it is brewed. To start with add all the organic matter you can find. You can buy some bagged compost. It is probably the wrong season now to find fall leaves, but in the fall collect all the leaves you can (I drive around and snatch up the bags of leaves people put at the curb). They are really good for your compost pile or to add directly to the soil. Grass clippings, pulled and chopped weeds (as long as they haven't set seed), peat moss, aged composted manure, shredded paper, straw, all are "organic matter" for your soil. Pile it on several inches thick (or more or less as thick as you can), till it in. Wait 2-3 weeks until all the weeds sprout and then repeat the whole process. Then you can plant in it, probably still in time to plant stuff for a fall crop. Throw in some of the worms from your worm bin in to the soil, to help break down all that OM you added.

The peat moss helps to acidify soil, so is a good addition. If your soil is highly alkaline, you probably need to add some sulfur with the OM.

This is someone else who just wrote in about their clay soil: ... =4&t=63913

Posts: 12926
Joined: Tue Jan 01, 2013 8:32 am
Location: Hawaii, zone 12a 587 ft elev.

Re: Heavy Clay Soil Amendment

The only way to tell if your soil is alkaline would be to test it? Did you do that or just assume from reading? If your soil grew anything on it before, it may not be as barren as you think, but it may be a hard pan to crack.
Organic matter helps and you may have to get some. If you have a composting facility near you, it would be cheaper to buy compost by the truckload than by the bag.

You can grow a cover crop to help actually do some of the work of breaking up the soil for you. The added bonus would be the biomass and possible nitrogen fixation if you use an inoculated legume that will add a lot of organic matter to the soil. ... 20area.pdf

Return to “Vegetable Garden Progress + Photos & Videos”