Rock hard in summer and a sticky mess in winter, clay may seem like the worst possible soil type to have in your garden, but it contains nutrients that feed plant growth and holds plenty of water, though sometimes too much water. Breaking up clay soil is the first step to improving it.
Clay soil is heavy. When digging or breaking up the soil in another way, rest and stretch every 10 to 15 minutes to help avoid the risk of injury.
In most areas of the United States, spring or fall is usually the best time to break up clay soil. Breaking the soil in winter when it's wet or in summer when it's hard and dry can be harmful. Digging into or tilling wet clay soil forms clods that plant roots cannot penetrate. The soil also becomes compacted. Digging or tilling hard, dry clay is back-breaking and may blunt or damage tools.
Break up clay soil when it's slightly moist. Dig 6 inches below the soil surface, and grab a handful of soil from the bottom of the hole. Squeeze the soil into a ball, and push your thumb into the ball's center. If the ball breaks apart, then you can start digging. If the ball doesn't break apart, wait until after a few days of dry weather to allow the soil to drain.
If your clay soil is never crumbly, only wet and sticky or dry and hard, then break it up after one to two weeks of dry weather.
Tools for the Job
Using the right tool for breaking up clay soil can save plenty of time and effort, and your back. Although a rototiller may seem the obvious choice, it isn't suitable. Rototillers usually penetrate only 6 to 7 inches below the soil surface. Lower soil layers must be penetrated to break up clay properly.
A garden spade can be used to break up clay that isn't too hard and compacted. Use a spade with a sharp, oiled blade to help penetrate the soil.
A trenching shovel's blade is narrower than a regular spade's blade. A slight V is at the trenching shovel blade's center, and the blade's end is sharper than a spade blade's end. A trenching shovel carries less soil than a spade, which can be beneficial because the strain on your back will be less when you lift soil with a trenching shovel.
Pick Ax or Mattock
A pick ax or mattock has a long, pointed, metal head at the end of a sturdy handle. Swing the metal head into the air by using the tool's handle, and then bring it sharply downward to break up a hard clay surface.
Pointed at one end and carrying a flat blade at the other, a breaker bar is a long, heavy piece of metal. Break up clay soil by lifting the bar into the air and dropping either of its ends onto the soil. Experiment to determine whether or not the flat blade or pointed end works best to break up your clay soil.
Miniature jackhammers are available for rent from equipment rental yards. A jackhammer is a power tool used to break up hard surfaces, such as concrete. Use a miniature jackhammer with a spade attachment to break up clay soil.
Wear long pants and a long-sleeved shirt, boots with steel toecaps, a hard hat, safety goggles and thick leather gloves when using a pick ax, mattock, breaker bar or miniature jackhammer.
Things You'll Need
Garden spade or trenching shovel
- Pick ax, mattock, breaker bar or mini jackhammer (optional)
Dig a hole 6 to 12 inches deep and 1 foot square with a garden spade or trenching shovel at one corner of the area of clay soil you want to break up. If a garden spade or trenching shovel won't penetrate the ground, then first loosen the soil by using a pick ax, mattock, breaker bar or miniature jackhammer.
Lift the soil you removed to make the hole, and put it in a wheelbarrow. Wheel the soil to the opposite corner of the clay soil area.
Break up the soil at the hole's bottom. Use the garden spade or another tool as necessary.
Dig a hole 6 to 12 inches deep and 1 foot square next to the original hole. Transfer the soil removed to make the second hole into the original hole, filling it. Break up the soil at the bottom of the second hole.
Dig and fill holes in the same way in rows across the plot of ground until you reach its final corner. Use the soil in the wheelbarrow to fill the final hole.
Don't transfer soil dug from a hole's low layer to another hole's upper layer. Subsoil in the low layer has fewer nutrients than upper-layer soil, and it is generally poorer in quality than upper-layer soil.