Soil is made up of both solids and open spaces. Mineral and organic materials occupy the solid spaces, while water, air, plant roots, and other soil organisms move through the pores (open spaces). The ever-changing mixing and movement of water and air creates a dynamic environment that drives much of the life on our planet. Soil is the only ecosystem that integrates the four major earth systems — the lithosphere, biosphere, atmosphere, and hydrosphere. It is the living, breathing skin of our earth, and without it life as we know it would not exist.
Through soil science we explore the nature of soil and its interactions with water, air, and biological resources to create a multi-layered combination of natural and anthropogenic landscapes. We can understand soil behavior and properties through three key areas:
- Soil Architecture: Texture, Tilth and Bulk Density
- Soil Water & Air: Infiltration, Storage, Leaching and Aeration
- Soil Dynamics: pH, Organic Matter and Minerals
A soil is approximately 50% solids and 50% pore spaces. In general, minerals make up about 45% of the volume with organic material making up 5%. These percentages of solid materials will change with climate and land use, but are fairly stable over time as compared to the dramatic changes of air and water in the pores spaces. The nature and arrangement of the solids in the soil volume is called soil architecture and controls the shape, size and continuity of the pore spaces.
While the total pore space remains approximately 50%, the percent of soil water and air will change, often daily, based on rain, evapotranspiration and drainage. Climate and management ultimately control the delivery of water, but the movement of air and water within the soil volume is determined by the nature of the pores. Water infiltration, storage, and leaching as well as air exchange with the atmosphere and respiration of soil organisms are driven by the movement of air and water within the soil pores. The soil architecture also determines the locations, pathways and abundance of roots and other soil organisms in the soil volume.
This ever-changing nature is soil dynamics and becomes most apparent at the interface of the solids and pores. These edge interactions (or edge effects) connect soil pH, fertility, mineralogy, toxicology, biology and much more to the functions and performance of soils. Whether meeting the needs of urban, suburban and rural stakeholders, guiding agricultural, forest or urban practices, as well as adapt to climate change and increasing natural resources pressures, understanding soil dynamics allows us to make informed decisions and successfully manage our soils.
To further your knowledge and understanding of this essential part of our lives and planet, visit the Lectures on Soil Science or some of the other SoilNOW offerings on our Innovation and Teaching webpage.
Please contact us at soil3@cornell.edu if you still have questions about this topic, and don’t see the information you need on our site. Remember, you can always navigate using the “Browse by Topic” section/sidebar.