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You want soil that drains well, yet retains enough moisture to keep the roots from drying out. You want soil that has a lot of organic matter for nutrients. You want soil that does not compact. You want soil that will allow roots to spread easily.
But how do you know what you have? Try one of these simple tests.
The Squeeze Test
Here's an easy test: Squeeze a fistful of wet dirt and release.- If it falls apart, your soil is too sandy or silty.
- If it holds together in a ball, press on the ball. If it breaks apart easily, you've got the right combination.
- If the pressed ball sticks together in a hard lump, looks shiny and feels sticky, you've got too much clay.
The Dissolving Test
Still another popular test involves soaking some soil overnight in water:
- Dig up a small amount of topsoil from your garden.
- Put the soil in a quart jar (fill just under half full) and top it off with water almost to the rim.
- Shake until the soil is dissolved and let it sit overnight.
The next day, you will find three different colored layers in the jar. The heavy sand portion will be on the bottom, with silt in the middle and clay on the top. There will also probably be some fine organic matter floating in the water. The more the merrier because the more organic matter, the more nutrient-filled your soil. Again, the optimum breakdown of the jar's contents should be 40 percent sand, 40 percent silt and 20 percent clay. You can also buy soil tests that will show you exactly what your soil is comprised of. For the home gardener, these are generally not necessary. You may, however, want to test your soil's pH level. Most plants grow best in a neutral pH but some plants, such as rhododendron and azalea, prefer acidic soils.
How To Fix Problematic Soils
Whatever type of soil you have, the remedy is usually the same: Amend the top few inches of soil with a couple of inches of organic matter or even with good loam. Organic matter not only provides nutrients, but it lightens heavy soil and makes it more (air and water) permeable.
Organic matter comes in many forms: compost, aged manure, peat, spent worm castings, etc. Whatever type you choose, make sure that it has been aged or rotted first. If you add fresh organic matter, it can temporarily take away nutrients from the soil as it decomposes. Not the intended result.
- Sandy soils: Sandy soils warm up quicker in the spring. They're easy to work and they offer good drainage. The problem with sandy soils is that they are composed of large particles that don't hold moisture (or nutrients) so you'll be forever watering and fertilizing. Adding organic amendments will help.
- Clayey soils: Clay is comprised of very fine particles. Clay soils are good in that they retain nutrients and water. But soils that have too much clay tend to be heavy and drain poorly, and they are often difficult to work. Again, amend with organic matter. Many experts advise against adding sand, which could have the unintended result of making "cement" in some soils.
- Silty soil: Be careful not to walk on silty soil or to work it when wet because it compacts easily. What to do? You've got it: Amend with organic matter.
- Loam: This is light fluffy soil that has just the right mix of fine, medium and large particles. It holds water long enough for the plant to absorb nutrients and water but lets the excess drain away so the plants don't get water logged. While this soil structure is optimal, it could always use extra nutrients. So, again, amending with organic matter can only make it better.
- "New" soils: If you're living in a new subdivision, your soil is probably poor. It could be filled with all sorts of rocks, fill and building debris. Plus, it was probably compacted by the heavy machinery during the building process. It will take you a few years to build your soil back up, but it can be done. Do yourself a favor and buy a truckload of good garden loam and work that into your existing soil. That will give your garden a good head start.
Amending a sandy or clayey soil will improve it but it won't make it loam — after all, you're only working with the top few inches. But over a course of years, you can certainly make a soil better.
If your soil is predominantly sandy or clayey, you might decide not to fight an unwinnable battle. In hopeless cases, just build a raised bed and bring in good soil.
