Digging loosens the soil so roots can penetrate more easily. But digging when the soil is too wet or too dry can ruin its structure. Dig only when the soil is moist enough to form a loose ball in your fist, but dry enough to fall apart when you drop it. Use a spade or spading fork to gently turn the top 8 to 12 inches of soil, mixing in the organic matter from Step 4. In vegetable gardens and beds of annual flowers, turn the soil only once a year in the spring before you plant.