For a better understanding of what kind of soil you've got, what it's made of, what kind of texture it has and how well it drains, read on. You'll also learn how to use old soil to rid your soil of weeds, pests and diseases.
Undercover Test
One of the best ways of gaining an understanding of your soil is to perform an undercover test. The test requires a fair amount of digging, so you might want to wait until you're ready to plant a new tree or shrub. Dig a hole 18 to 24 inches deep and wide, piling the excavated soil nearby. Get down on the ground and look closely at the sides of the hole. What you'll likely discover is a series of soil layers. The first layer is topsoil, and it should be at least 6 inches thick and fairly fluffy. The remaining layers, whose thickness and densities may vary considerably, are generally referred to as subsoil. Now look at the roots in the soil. In healthy soils, they grow straight down, but in poor soils, roots tend to grow horizontally due to a thin layer of topsoil or compaction in the subsoil, or both.
The different colors of the layers are probably the best indicators of soil health, and generally speaking, the darker the color, the better the soil. For instance, dark browns, reds and tans suggest soils with a high humus content. Soils with a blue or gray tint are indicators of poor drainage, usually a result of compaction.
Now look at the excavated soil for signs of life. It should contain a fair number of earthworms as well as other critters. If it doesn't, the soil either lacks sufficient organic matter or has been maintained far too long on a diet of harsh, synthetic fertilizers. Actually, the undercover test isn't so much a test as it is an observation. It can reveal all sorts of problems related to a lack of organic matter, compaction, poor drainage and the like.
If you use a rototiller a lot, the top 8 to 10 inches of your soil may be nice and fluffy, but below that, hard as a rock. That's because excessive tilling can lead to the creation of something called hardpan, a layer of subsoil below the reach of the tiller's tines. You can drive a pitchfork deep into the subsoil each time you till, to loosen the hardpan layer.
The Watering Test
Start by watering your lawn or garden thoroughly. Two days later, dig a 6-inch hole and check the moisture content of the soil. If the hole is dry at the bottom, your soil is draining too quickly for most plants to grow properly. If the hole is soggy, your soil isn't draining fast enough. So how do you deal with soil problems? Whether your soil has too much sand or too much clay, drains too slowly or too quickly, or lacks sufficient nutrients and soil organisms, the solution is the same in every case: organic matter. Compost is the best source of organic matter. If you've got good soil, but each year you have problems with weeds, pests and diseases of one form or another, use a technique known as soil solarization, which is best done during the summer months.
Soil Solarization
First, rake the problem area smooth, getting rid of any clods along the way, and level it. Then water the area, soaking it more than usual. The next day, cover the area with 3- to 3-millimeter clear plastic, covering the edges with soil to hold it in place. Within four to six weeks, the greenhouse effect caused by the sun hitting the plastic will cause soil temperatures beneath the plastic to reach between 140 and 160 degrees Fahrenheit, which is hot enough to kill almost everything in the soil. At that point, you can remove the plastic and plant away.
Squeeze Test
To literally get a feel for the content and texture of your soil, perform a squeeze test, for which you need a handful of soil from your lawn or garden. First, roll the soil in your hand until it's about the size of a golf ball. Then gently squeeze the soil between your thumb and index finger. Sand feels gritty, silt feels more like talcum powder and clay feels slippery. Now squeeze the ball in your hand. If it crumbles, it has a well-balanced texture. If it holds its shape, it has a fair amount of clay. And if you can roll it into a snake, it has more clay than you want.
Perc Test
Drainage problems account for an incredible number of problems in the lawn and garden. If the soil drains too quickly, plants may never have a chance to absorb enough water to adequately sustain their growth, no matter how often you water. And if the soil drains too slowly, plants may actually suffocate or rot. That's why it's a good idea to perform a perc test.
Dig a hole 6 inches wide and 1 foot deep using a shovel or post-hole digger. Then fill the hole with water and let it drain. When the water has drained completely, fill the hole again, and this time keep track of how long it takes for the water to drain completely from the hole. If the water drains completely within 3 hours or less, you have a drainage problem, probably due to sandy soil. If water is still standing in the hole after 8 hours, you have a drainage problem due to too much clay in the soil, and if the water drains within 4 to 6 hours, you don't have a drainage problem.
