Ideas for clay soil amendments and soil compaction reduction

While tilling clay soil today I made some observations about the wetness of the soil and began to recall how to prevent soil compaction throughout the season. As I was man handling our 1950’s tiller I realized this is the chump’s way of doing things.

The problem with clay soil is that it holds water well. That can be great for some plants during the season if you can reduce soil compaction, but it is lousy if you want to get an early start to your garden. This spring has been unseasonably cold for a long time. Even though we haven’t had a really wet spring, that clay soil stays wet long enough to make getting started early impossible.

But what can be done different? First, consider efficiencies. Are you doing more work than you need too? Here’s a list of ideas.

Are you working the whole garden when you only plant a little bit? Consider raised beds.

Yes, it has been tradition for us to just go till up the whole garden in the spring, but that is a real chore. Some plants don’t even need it. Sure, every year when I pull the tomatoes out of our clay soil I get surface roots 6 feet long that extend to rows of other plants. But that isn’t the case for every plant. For example, carrots grow downward, not so much outward and are quite self contained. Peppers are incredibly shallow rooted and roots stay close to the plant.

For plants like this you should consider building raised boxes just big enough for one or two rows planted at your favorite spacing. The benefit here is that you can add all the compost, mulch and soil amendments you want to these beds easily. You can also till it in a couple minutes if you like. In my experience I can till from one end to the other on a 15 - 20 foot bed with good soil in 30 seconds. In fact, because you are only adding soil amendments to such a small area, the soil will probably take shape in a year and you can work it with a shovel easily. If you don’t use raised beds then soil amendments you apply to one row usually get spread around the garden the next season. In that case, the soil from this year’s well treated row of peppers could be tilled and spread into next year’s adjacent walking path.

Overhead irrigation is compacting your soil! Use mulch, soaker hoses and alternate irrigation.

Overhead water sprinklers are still a great way to water lawns and large areas quickly, but when you use them to water a garden you can waste a lot and compact that already heavy and wet clay soil. First things first, try your best to conserve moisture using mulches so you don’t have to water as often. I use black plastic mulch on peppers and melons, dried organic matter mulch around other plants, and living mulches like barley wherever I have spare room. Barley is very shallow rooted so I grow it in between my tomatoes when they are small, then just before it goes to flower I pull it out with my hands (very easy), lay it on the ground to dry until it is like straw, then I put it around any plants that need it. At the end of the season it is tilled into the soil to add rich organic matter. The real advantage to conserving moisture with mulch is that you water less, and that compacts the soil less, reducing the need for working the soil.

Alternate irrigation like soaker hoses and drip irrigation are another great way to regularly water garden rows. A soaker hose (“weeps” water all along the hose length and diameter) can be laid under any mulch, including plastic. Drip irrigation (a tube with small openings called “emitters” placed near the plants) is great for peppers because you can put an emitter at the base of each plant and set it on a timer for 15 minutes a day or so. Again, if you aren’t watering areas that you don’t use then you save money on watering, and keep from compacting the soil so quickly. And that leaves air spaces in the soil, which is one reason you till to start with.

Enrich your soil by adding soil amendments.
One way to help get an early start to your garden if you have clay soil is to add soil amendments. Yes, you can improve clay soil, and improving clay soil is by far the most important way to reduce soil compaction caused by clay soil drainage issues. This will help it dry out faster in the early season so you can plant sooner.

My favorite soil amendment on clay soil is alfalfa. You can buy alfalfa meal to add to your soil but I prefer growing it wherever I have space. If you have never done this before and can spare 50% of your garden, I suggest starting by planting half your garden in alfalfa for 1 whole year and then next year the other half, and you’ll be on your way to a nice rich soil. Otherwise do what I do and plant a little each year in your fallow areas before the season starts, after the season is done, and in between rows on walking paths, etc. Plant the alfalfa and let it grow until you see flowers, then cut the greens down, which will decay will add nitrogen to the soil. Then let the tops grow again. When the end of the season comes cut them down again, and use a shovel to break the crown just below the soil if you don’t have a sharp tiller, otherwise till into the soil. Alfalfa roots are so deep, that when they decay it is like adding compost several feet deep into your garden. But you have to grow them a full season at least if you want those deep roots. Take a look in your favorite seed catalog, like Johnny’s Selected Seeds, under “green manure” for options on planting alfalfa and other varieties of living mulch.

Till in the spring AND fall

I’m kicking myself this year for not tilling in the fall, but the previous year I did and found the spring tilling to be much easier. Why? First, you get it before it becomes frozen, snow packed, thawed and heavy. Second, the uneven surface created by tilling exposes more dirt to air, meaning it will dry faster for earlier spring working. Third, it brings some of those clay lumps to the surface and after they are exposed for the winter and dried in the spring they break down into dust which means you shouldn’t have so many lumps to deal with. Lastly, fall tilling will give you a chance to add any soil amendments like dried fall leaves right away giving them a whole season to break down, and will allow you to easily do a winter planting (scattering) of your favorite green manure or cover crop to help prevent erosion and enrich the soil even further. Doing a fall till will make spring tilling easier, earlier, and help get rid of some of those clay lumps.

Tilling wet clay soil in the spring is messy, creates more lumps and kills earthworms that are close to the surface in the tilling zone. You can reverse this by looking at efficiencies. Don’t water where you don’t plant. Use alternate watering methods that only put water where it is needed. Mulch the ground so you don’t have to water as often. Minimize soil compaction. Plant green manures and cover crops in fallow spaces and over the winter to enrich that clay soil with amendments that provide real benefit to your plants and will help to change the structure of that clay soil into something a little easier to work. Looking after these few things will make your gardening experience a bit more pleasant, save your health if you do your own tilling, and get you planting a little bit earlier in the season.