Soil covers a major portion of the Earth's surface, and is an important natural resource that either directly or indirectly supports most of the planet's life. Soil is a mixture of mineral and organic materials plus air and water. The contents of soil vary by location and are constantly changing.

The ORNL DAAC Soil Collections archive contains data on the physical and chemical properties of soils, including:

• soil carbon and nitrogen
• soil water-holding capacity
• soil respiration
• soil texture