The best soil, sandy loam, for most plants is rich in nutrients, well-draining and has a neutral or near-neutral pH. Loam allows the movement of water, air and nutrients to plant roots. Because roots are able to fully develop, plants are better able to withstand wind and drought when grown in loam.
Soil is composed of mineral particles, water, and air. Varying particle sizes made from sand, silt and clay leave spaces in the soil for water and air movement. Loam consists of about 50 percent sand, 20 to 30 percent silt and 20 to 30 percent clay. To test your soil, squeeze a handful of soil into a ball. Soil with too much sand sifts through your fingers. Soil with too much silt feels like talcum powder and won't form a ball. Soil with too much clay forms a sticky ball and won't absorb water. Garden loam forms a loose, crumbly ball.
Use organic matter, decomposing plant and animal materials to correct soil with poor drainage. In varying stages of decomposition, organic matter stimulates microbial activity and adds nitrogen and other nutrients to the soil. Add organic materials, such as grass clippings, leaves and composted materials, to the garden at least three weeks before planting time.
A healthy population of microorganisms, such as protozoa, bacteria and fungi, and small animals, such as earthworms, live in garden loam. These organisms aerate the soil and convert organic matter into nutrients for root uptake. Add compost and plant materials to the soil to increase organisms in the soil.