If you’re faced with a garden of clay soil, you know that amending clay soil is on your short list (number one) of garden tasks. You’ve probably known other gardens or gardeners afflicted with this tough garden condition. It’s enough to make you wonder if you can ever achieve that ideal loam you need for a productive and prosperous garden. Here, we’ve got the long and short of the steps to success.
The first thing you want to do is assess the degree of your problem. Take some random samples of the soil from all around your garden. This is most easily accomplished with a shovel, preferably when the soil is just moist, not wet. Take a small amount – a couple of tablespoons is adequate – and roll it into a ball. Now, take just a pinch from the ball between your fingers. If the soil breaks or crumbles, it’s tillable. However, it’s more likely that the ball of clay soil will have a sticky consistency. Try flattening your sample into a ribbon a few inches long. If you can do this, your work is cut out for you. Amending clay soil, in this case, will be an ongoing process, which may require a few seasons before you’ve got that highly desirable loam. You’ll need patience, but with each successive step, your soil quality improves.
Now, you’ll want to get a soil test kit, taking samples from each location you initially dug. When you’ve obtained the results, you’ll know the particular amendments you’ll need, such as phosphorous, lime or gypsum, to bring your clay soil up to growing snuff.
When amending clay soil, you want to be careful of the type of sand, if any, you add to the existing soil. Many gardeners assume that quantities of sand will counteract that stickiness in a positive way. If the sand you choose is not quite sharp, you can end up with soil that’s worse than when you started! Consult with your nursery for more advice on this addition.
For the first round of treatment, you’ll want to add plenty of organic matter, which improves your soil structure, amending soil that’s sticky and compacted and leads that soil to a looser consistency. Compost and manure are excellent for this purpose. Depending on the size of your garden and its condition, you may need a truckload delivered from a compost supplier, to be incorporated in layers an inch or two in depth with each pass.
As you begin, do so when the soil is not wet! Dig your bed to a depth of 10-12 inches, laying the clay to the side. Add your compost and manure in 1-2 inch layers, followed by 1-2 inches of clay, working the composite layer lightly to avoid compaction. (No one would ever say that amending clay soil is easy, but the eventual rewards are great, so keep at it!)
By the time you’ve worked in all of your amendments, you should have soil that’s plantable. It’s important that you don’t go crazy with a tiller. Gently working each layer of amendments in to the soil provides enough for now.
Depending on the season, one invaluable resource in amending clay soil is in planting cover crops. Planting rotations of cover crops is even better. Green manures, such as alfalfa, and legumes work wonders in amending clay soil. Try red clover, oats, vetch or rye. Again, consult your local nursery for cover crops which grow well in your area. Legumes are especially valuable, in that they help fix nitrogen in the soil. Cover crops also serve to keep weeds at bay, either by killing weed seeds altogether or preventing germination of weeds. Cover crops go a long way in amending clay soil and result in significantly more friable soil. You and your tiller will be thankful for this, come spring planting time! Work the spent crop into the first few inches of soil.
Following this program of amending clay soil, your sticky, impervious soil will improve. You’ll get better drainage, less crusting (that unattractive display of infertile, cracked soil) and reduced erosion.
So, you can see that amending clay soil requires patience, but in the end – and all along the way, your dreams of that fine loam creeps incrementally into your garden. Good luck and happy gardening!