Amending refers to changing the condition and function of the soil, rather than adding nutrients to it (which is known as fertilizing). The conditions that really matter are drainage, retention of nutrients and moisture, density, stickiness, and pH.
Soil is made up of clay, silt, and sand. The right balance of these, mixed with organic matter, results in loam. Loam holds together (unlike sand), but is soft and crumbly (unlike clay). Loam is desirable because it:
The soil in Western Washington is mostly volcanic and glacial till. You’ll find it has a high clay content, and is on the acidic end of the scale. Clay needs to be broken down. Plants can struggle in clay-heavy soils because nutrients and moisture permeate slowly and inefficiently, and roots can’t penetrate effectively.
Amending for lawns
A mixture that is two parts soil, one part sand, is ideal. The sand helps with groundwater drainage. You can either top dress the native ground with 3-4 inch layer, or till the native ground and mix your new soil in. Try our 3-way topsoil, which is sand, loam and compost.
For best results, till 3-4 inches down to break up the clay. You’ll need to mix in a loam that is rich in nutrients. Start with a soil like our 3-way topsoil, and add compost as needed. We recommend running a compost system to make use of kitchen and yard waste. If you need more compost than you can produce, bulk compost is available at our yard next to the fairgrounds.
Amendment is usually simple and fairly predictable. We recommend starting simple, as described above. This ought to produce results, and necessary changes can be made as needed.
Do I need to test the soil?
You can most likely eliminate this step for lawns. Different plants in the garden will have different needs. Do your homework on your crops to learn what the target pH is. You may find all your plants can thrive in the same range. A simple testing kit can be picked up at your local garden center. Apply the following amendments, as needed:
Compost adds nutrients and increases retention of moisture
Organic matter can be mixed directly to the top layer to increase nutrients. Try rotted manure, or small bits of straw and leaves.
Lime will reduce acidity, moving the pH of soil up the scale toward neutral (7) or beyond it into the alkaline range of 7-14.
Sulfur reduces alkalinity, moving the pH toward neutral (7) or beyond it into the acidic range of 1-7
Gypsum works to loosen up stubborn clay
Call on the Waeco stockyard by the Evergreen State Fairgrounds in Monroe for bulk materials needed for your lawn and garden projects. Topsoil, organic bark mulch, sand, gravel, and washed rock are available by the truckload.