What Nutrients Are Missing in Clay Soil?

Understanding Clay Soil

• Clay is the smallest soil particle, and it makes your soil dense and sticky. When your garden soil has too many clay particles, it will not drain well and will compact easily from watering or working the soil. Because water remains around the roots, your plants cannot access oxygen or nutrients for plant growth. Soil high in clay particles may contain all the nutrients your plants need for healthy growth, but your plants cannot use them.

Improving Clay Soil

• Many gardeners assume that because clay soil is dense and compacts easily that adding coarse sand to the soil will improve its texture. Although this seems logical, it can have devastating effects on your soil. When sand is added to soil high in clay particles, the two bind together to form a natural cement, leaving the gardener with more problems than he or she had in the first place.

  Adding organic matter, such as compost, peat moss or well-rotted manure, lightens the soil and creates the air pockets your clay soil needs. Although some garden experts, such as the Utah State University Extension, recommend amending clay soil with both organic matter and coarse sand, others, such as Colorado State University Extension, caution against adding sand to clay soils and recommend amending with organic matter only.

Ideal Composition

• Good garden loam should contain a combination of sand, silt and clay with only 10 to 20 percent of the total volume consisting of clay particles. The other 80 to 90 percent of your soil should consist of equal parts sand and silt.

Necessary Nutrients

• Plants need nitrogen, phosphorus and potassium in relatively large amounts for healthy plant growth. These nutrients are referred to as macronutrients. Although they are required in lesser amounts, sulfur, calcium and magnesium are also considered macronutrients. Nutrients such as zinc, iron and boron are sometimes referred to as trace nutrients or micronutrients because they are needed in minute amounts.

Soil Testing

• It is impossible to tell which nutrients your clay soil may lack without a soil test. A quick home test will provide the levels of nitrogen, phosphorus and potassium, but it will not determine whether your soil lacks micronutrients. Soil testing through a university extension or through soil testing services in your area will give you a better picture of the nutrients your soil contains. Many provide a detailed report with directions for amending the soil to balance nutrients.