Soil Drainage

It's been raining again this evening; just light showers at this point, but the soil is already saturated, and water is standing in the yard in places. In part, this is simply because we've had so much rain over the last couple of weeks that there's a flood watch in the area. But it's also because the soil in my yard tends to be a heavy clay, that doesn't drain very well.  I've observed that lower-lying areas in my yard, water pools up after heavy rains.

Are you unsure of how your garden soil rates on drainage? Sometime when it isn't rainy, try this test. Dig a hole about a foot deep, and about as wide as your shovel. Fill the hole up completely with water, and leave it to drain out completely. The next day, go back and fill it up completely again. This time keep an eye on it to see how long it takes for all of the water to drain away.

If the water all soaks into the soil in a few minutes, your soil drains too fast. It probably has a very high percentage of sand; and doesn't retain moisture or nutrients well enough for plants to grow well.

If the water takes more than an hour to soak in, then you have poor drainage. Your soil is probably clay, which means it is made up of very fine particles that stick to each other, and pack down hard. This kind of soil has very poor drainage and limited aeration. Plant roots need air as well as water. If roots have no oxygen for a long time they can suffocate.

Whether your soil is poorly drained or drains too fast, the solution is the same—add compost, composted manure, leaf mold or fine pine bark. Some people add sand to heavy clay, but this can actually decrease drainage. Organic matter is better. Ideally soil is about half solid matter and half porous areas filled with air and water.

Earthworms will also help improve drainage in your soil. Their tunnels give water places to drain away, and they move nutrients and organic matter down through the soil. I think of earthworms as really slow-motion rototilling, without harming plant roots. Ants can be real pests, but their tunnels can aerate soil too.

Avoid walking on or working your soil when it's really wet, as this compacts the soil. I have permanent paths of stepping stones through garden beds, so I can reach areas for maintenance without walking on the soil.