Clay Soil

Hi Folks,

I just returned from the site of my future garden, and what did I encounter? Clay Soil. A PH of 4.5 and very little sign of any organic matter.

Does anyone have experience improving clay soil?

I was originally planning to rototill and prepare my soil this weekend, but given the rain in the forecast I'm quite hesitant.

Do you think it would be wise to proceed w/my soil prep given the wet forecast for next week?

Thanks!,
Josh

Hi,

How did you measure the pH? Your reading does not sound reasonable for clay in our area, which usually read over a pH of 7. We are not known for acidic soil in this area, though your reading may be right. I'm just surprised.

To rototill or not to rototill has a lot more to do with soil conditions right now and not because of rain in the forecast. If the soil is saturated now, it can be formed into a solid lump by squeezing with your hand. If it falls apart, then the soil can be rototilled. I am referring to soil, not clay.

Is your plot on your property or a public garden? While you have to work with what you have for the moment. An ambitious program of adding organic material and rototilling is great to do in the fall, because it has all winter to break down.

The University of Illinois Extension has a useful website devoted to vegetable gardening you may want to consult.

Soil Preparation and Fertilization
Before you can plant, soil preparation is a must. Dig the soil to a depth of at least 6-10 inches. Add a two to four inch layer of organic matter and incorporate it into the soil. Organic matter will improve your soil structure and will add nutrients to the soil.

Vegetables need nutrients to grow. A good vegetable garden fertilizer should have an analysis of something like 5-10-5, 10-10-10 or 12-12-12. The first number stands for the per cent of nitrogen, the second number the per cent of phosphorus and the third number the per cent of potassium. Nitrogen promotes green growth, phosphorus promotes root growth and fruit development and potassium promotes disease resistance and root development. If you are growing your vegetables organically, organic fertilizers like peat moss, compost or composted cow manure are a good source of nutrients for your vegetables.

Regards,

Hi Kathy,

Thanks for the info.

At the moment, my soil is waterlogged and apparently not ready to prepare. It sticks together like glue when I press it together. My only fear in this is that by waiting I'll only allow it to get soggier.

As for the PH test, I used an insta-read PH tester. Perhaps its not accurate? I'm thinking of going to the store to purchase a paper-based testing kit just to make sure.

The land I'm on has been gardened / tilled every year for the past two years. The drainage looks poor, and the soil looks generally dead. It doesn't have much of an odor at all, and the serious clay seems to begin about 8 inches under the surface.

Thx,
Josh

Hi,

When I was a Master Gardener Volunteer, we often encountered people in new developments with maybe two inches of top soil over clay (and sometimes construction debris). We always advised them to rototill the soil into the clay, which seems counterintuitive. If you didn't the grass and other plants would develop shallow root systems trying to stay in the top soil. Top soil tilled into the clay not only aerated it, it encouraged grass and plants to root deeper.

If your clay is 6 inches under the soil, you don't have too much to worry about.

Soggy and soggier soil should be left alone. If you do too much when it isn't ready, you could cause compaction that is another problem. Like it or not, gardening teaches you patience.

Regards,

Indeed. I would rather err on the side of caution than damage my soil any more than it is.

Would it be wise to spread incorporate some of my organic matter before the rains / before I till or should I just wait until I'm ready to till in all of my organic matter?

I don't have Cathy's experience as a MG, so take this simply as my recollection of what I did.

I certainly had very heavy soil when starting out. I had a horse, so was lucky in the sense that I could let the manure mature each year and add it. I also had my own compost bin. Then I'd buy other amendments, such as peat. I always waited until it was relatively dry - the window in the spring is short in my past experience. Either you get to it before the rains start (which I rarely did) or after they stop, which I almost always had to do. I'd take a quick pass with the rototiller, then add amendments, then till thoroughly. Each year I did the same thing until I had lovely soil. It took a couple years to get good soil and several to get great soil.

Lastly, in the fall, if I would remember and had time, I'd occasionally clean the bed and then plant a nitrogen fixing plant like vetch. In the spring, I'd till it under. Another source of organic matter that both added nitrogen and lightened the soil.

I just did a search to see if what I did was in line with current methods. There are some great discussions on the garden web forum such as the one I just linked to (there are many others there, too). While looking, I also found this pagewith an interesting way to test your soil for composition - a glass jar and water, with a bit of Calgon!

Just my experience, but found that most inexpensive soil pH tests were wildly inaccurate and had to buy a decent meter. Also seem to remember that you need to test in multiple places as it can vary.

Do not work clay soil when it is too wet because you will create all sort of compaction problems. Consider what happens working on a potter's wheel. You will do that outside finish on every blob of soil contacted by you spade, hoe, rotary tiller, etc. Rain will break down the clods to some extent, but it will require a winter of freeze-thaw cycles on roughly spaded land to break them apart fully. Roots will not penetrate those clods. Clay can be tricky because the margin between too wet and too dry may occur in a short period of time. Squeeze a handful of soil. It should fall apart when you let go.

The only thing that works on clay soil is organic matter--lots of it. My gardens in Chicago started with horrible clay including some of the gray stuff used to make bricks. Nobody seeing the soil now would know what a mess it was.

Sand may make the soil scour better on implements but will not soften dry soil. In fact, it can be worse than straight clay. I now own a farm with sandy clay soil where as a teenager I had to stop plowing after wheat harvest because a moldboard plow would not penetrate dry soil. You had to disc to control weeds and mix straw into the surface and then wait for rain.

Be careful not to overtill with a rotary tiller because rain will smash down the fine particles into an impenetrable mass.