Q: About three years ago we tilled up our hard clay front yard and added close to a half-ton of compost and soil amendments. The soil looked really good when we finished. This year, when I dug around some shrubs, the soil was back to mostly clay. Where did my compost go? I can’t dig up my yard every three years to amend the soil!
A: Some of your compost cooked away, some eroded away and some is still there, in the form of humus. Gardeners feel a great thrill when their bad soil has been amended with compost and changed for the better. Imagine, though, what would happen if you put vegetables and water in a slow-cooker and let them simmer, covered, for three years. You would have nothing but thin gruel – not distinguishable carrots, peas or potatoes.
The great compost you added to your yard has slowly cooked for the past few years. Particles on top of the soil turned to dust and blew away. Compost is lighter than clay and tends to wash away when it rains. Underground, soil creatures ate and digested large compost fragments. They excreted what they couldn’t use in tiny grains, called humus. Humus is great stuff because it holds nutrients for your plants. However, it is so finely divided that is packs down with the clay around it.
Your once-beautiful soil has begun reverting back to its former state. You can reverse the process by adding a one inch layer of composted cow manure under and around all of your perennials and shrubs. Keep it away from plant stems and cover with a thin layer of pine straw. During the summer, earthworms will find the rich food and will gradually work the manure into the soil. Over the next three years your soil will improve by itself, without any work on your part!
Lest you imagine that any clay soil can be enhanced with this no-till method, let me point out that tilling the soil three years ago was essential to the process. You oxygenated the soil and made it more attractive for soil organisms. You just forgot to feed them what they needed during the ensuing months. Check under your plants next spring. If the manure is gone, it’s time to feed your soil once again.