The most basic factor you need to know about is soil type, which is the composition of the soil’s particles you inherit in your garden. Knowing your soil’s type helps you determine what you need to do to build healthy soil.

Measuring Your Soil

Soil comes in three main types, each with its own strengths and weaknesses:

• Clay: Clay soil has the most potentially high natural fertility but can be difficult to work with. Clay’s individual soil particles are so small that water and air have little room to squeeze between them. Clay soil stays wet longer, contains little oxygen, and dries as hard as concrete.
• Sandy: Sand particles are large, leaving plenty of room for water and air to move between them but allowing sandy soil to dry out quickly. Nutrients leach through sandy soils quickly, too, making them naturally less fertile and more prone to drought.
• Silt: Silt soils have moderate-sized particles that hold some water and air but also allow the water to drain. They have moderate amounts of fertility, are easy to work with, and make life easy for the gardener.

You may have heard some gardeners singing the praises of loam — soil that consists of roughly the same amounts of sand, silt, and clay. It holds optimum amounts of water, oxygen, and nutrients for most plant growth. If you’re lucky, it’s in your yard already. More likely, you need to amend your soil to work toward loam’s balance.

Your soil is probably a mixture of sand, silt, and clay, but to find out the predominant type of soil in your garden, reach out and touch it. Take a small handful of damp soil in your hand and rub a pinch of it between your thumb and pointing finger. If it feels gritty, it’s mostly sand; if it feels slick and slimy, it’s mostly clay. If it feels like something between those two, it’s mostly silt.

For a more accurate measurement of the amounts of clay, silt, and sand in your soil, do the jar test. Here’s how:

1. Collect soil from several places in your garden.
2. Mix the samples thoroughly and measure out 1 cup of the mixture.
3. Let the soil air-dry on a sheet of paper until crumbly.
4. Crush chunks until the soil is very fine, removing any stones and debris as you do so.
5. Place soil in a narrow glass jar, such as a pint-sized canning jar, and add 1 teaspoon of nonsudsy dishwasher detergent.
6. Fill jar 2/3 full of water, seal, and shake vigorously to mix the contents.
7. Put down the jar and start a timer.
8. Measure and mark the level of settled soil after 1 minute. This soil is sand.
9. Measure again in 2 hours and subtract the sand layer to find the amount of silt. After several days, the clay settles out on top of the sand and silt.
10. Measure this top layer, subtracting the sand and silt to find the amount of clay.  ....read more