In agriculture, soil tests are generally carried out to determine the nutrient content, composition, acidity or pH value of soil. Since soil nutrients vary with depth, as well as soil components vary with time, the depth and timing of the sample taken from the soil for testing affects the results.

Soil testing is an important tool for determining nutrient needs of plants and for environmental assessments. Some soils are naturally deficient in plant nutrients. Some soils have lost their nutritional properties over time, although they have had sufficient nutritional properties in the past. Soil testing is widely performed in crop production areas around the world to understand the fertilization needs of plants.

Soil tests are also performed to determine the application rates of nutrient-containing wastes or other elements that may harm the environment. Waste materials such as animal manure and industrial by-products may contain a variety of plant nutrients.

However, such substances that are released to the soil at a high rate are harmful to plant, animal or human health. Several regulations have been enacted to assess environmental damage levels of certain chemicals and to limit their use. At the same time, these regulations require soil testing.

In advanced laboratories, soils are regularly tested for primary nutrients, phosphorus, potassium and nitrogen. In some regions soils are also tested for other primary nutrient contents such as calcium, magnesium and sulfur, and elemental contents such as boron, copper, iron, manganese, molybdenum and zinc. In case of doubt, soil is also tested for arsenic, cadmium, nickel, lead, mercury and selenium wastes.

Nitrogen and potassium, one of the primary plant nutrients, have harmful effects on the environment when applied to the soil in excessive amounts.