Soil quality refers to the suitability of the soil for supporting plant and animal life. Soil is made of a mixture of rock fragments (that can range from fine clays to large sedimentary grains), organic matter, gases (carbon dioxide and oxygen), water, and organisms such as bacteria that cycle nutrients that help support the growth of other organisms the depend on the soil.
Credit: USDA
Soil plays important roles in the Earth system, including:
- Providing essential nutrients and habitats needed for productivity, including food production and biodiversity.
- Filtering of water borne pollutants and toxins thereby improving water quality.
- Providing a reservoir for carbon.
Soil quality is affected by many Earth system processes and phenomena, including:
- The rock cycle, especially rates of weathering and erosion. The type of rock weathered plays a major role in determining the chemistry of the soil and the soil chemistry, and the size of the soil rock fragments helps determines which species of plants and animals can live in the soil.
- Nutrient levels, especially nitrogen and phosphorus, which when limited can decrease productivity and biomass, and food availability and nutrition.
- Human land and water use, including deforestation and agricultural activities. Removing trees and other plants, plowing fields, and overgrazing by livestock destabilizes soils and increases their rates of erosion by 10 to 100 times.
- The release of pollutants and waste from pesticides and fertilizers into soil, which can harm the survival and growth of organisms.
- Urbanization, especially paving land with concrete, increases water runoff, which can increase erosion and decrease soil quality.
- Damming rivers and extracting water from freshwater ecosystems for human use can decrease erosion and change soil chemistry and texture.
Can you think of additional cause and effect relationships between soil quality and other parts of the Earth system?
Visit the rock cycle, nutrient levels, and productivity and biomass pages to explore more connections between the biosphere, geosphere, and global changes.