If you have a heavy clay soil, then you know what a challenge it can be to grow in it.
When many of Chicago's neighborhoods were built, they were leveled out with a bulldozer. The developers often scraped off all or most of the topsoil, leaving behind nothing but the heavy clay underneath.
Clay particles are small and pack in so tightly that water can't get between them easily . That's why clay soils drain so slowly after rains or irrigation (which can drown some plant roots). When they do finally dry out, they form a hard, cracked surface.
Here are some tips on making clay soils easier to deal with.
Add Organic Matter
This is where compost comes in. Whether you have a compost pile at home or some bags of mushroom compost, cow manure, or organic peat, spread it around your yard before your spring plantings. Not only does this add nutrients back into your soil, but it provides food for beneficial soil microbes that, in turn, help to soften your soil. A 2-3 inch layer worked in to shovel depth is a good amount. You can also use a half inch spread sparingly over established lawn areas. Since soil microorganisms literally "eat" organic matter, be sure to replenish their food supply throughout the growing season.
Build Raised Beds
Since clay soils have poor drainage, try building a raised bed. By raising up the soil level, you encourage better drainage. Be sure to fill the beds with a light, free draining soil. To make your life easier, size the beds so that you can reach to the middle of it without having to step in it.
Sorry, Sand Won't Work
Most people believe that adding sand to a clay soil will improve drainage. This is only partly true. Sand will help improve drainage, but only if you add A LOT of it. Sand would need to be incorporated to about 50% of the total soil volume to see a noticeable difference. You'd need some pretty heavy machinery to do that kind of mixing. Unfortunately, adding smaller amounts of sand can have the opposite effect and make something that resembles concrete. So, unless you're renting a front end loader, Don't do it.
Adding mulch as a soil cover not only helps reduce compaction and erosion, but it also slowly helps improve soil structure (mulch is after all, organic matter). It also helps avoid that overly hard, cracked soil surface that is quite unsightly.
Improving clay soils can take some time, so don't expect results overnight (unless you got the heavy machinery and about 40 yards of sand). But by adding in compost each year and keeping your soil micro-organisms happy, you should notice that your soil improves a little more every year.