From Bulb and Blossom Garden Club
Friendly soil structure is one of the most overlooked features of garden soil. Great garden soil is only about 50% dirt; the other parts are air and water. Friendly soil provides access to air, nutrients, and growth for tender roots. A garden that is full of heavy clay or dry loose sand is not friendly to plant roots, making them work harder than necessary.
Friendly soil feels different than dirt that is nutrient-depleted. The hand grab is one of the fastest and easiest ways to determine what the structure of soil is and how well it functions. Balanced soil has a softness and a give to it but still holds it shape. When you close your fist, the soil clings together gently, but crumbles easily between your fingers. Soil that has too much clay will be compact and barely crumble, and soil that is too loose to hold a shape and feels gritty has too much sand in it.
There is a simple soil test that will tell you what percentage of garden soil is clay, silt, and sand. You will need a Ball jar (or any straight sided jar), a tight-fitting lid, a ruler, and laundry or dish detergent. Fill the jar about half full of soil from the garden. Be sure to remove any rocks or debris. Add water until the jar is three quarters full and add a teaspoon of dish soap. The dish soap will separate the layers of soil.
Tighten the lid and shake the jar thoroughly for about 3 minutes. Leave the jar undisturbed for 24-48 hours. When the settling is complete the water on top will be clear. Under the water the soil will have settled in 3 layers; clay on top, silt in the middle, and sand at the bottom.
The ideal combination of these 3 layers is 20% clay, 40% silt, and 40% sand. To find the percentage of your garden soil, measure the total inches of the 3 layers (exclude the water layer). Next, divide the inches, or fractions of inches, of each layer by the total inches of all 3 layers and multiply by 100 to get the percentage of each layer.
Rarely will any garden soil match the above percentages, but these simple tests help you better understand your soil’s structure and corresponding aeration and drainage properties.
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