What is soil?

Written by Ethlyn Koh
Photos by Goh Shang Ming

Every day as you lay your feet on the ground and walk the earth, have you ever wondered what lies beneath? Soil. This material exists on the outermost part of Earth’s crust, forming the surface of land and sometimes regarded as “skin of the earth”. 

The uses of soil are endless. 

Soil is an important natural body as it supports agriculture. Most of the food we consume can be traced back to soil because it is the original source of nutrients needed to grow and produce food. Soil also plays a crucial role in the water cycle. Not only does soil store and filter water, providing a clean supply of water, it too improves our resilience to floods and droughts, especially in the face of climate change. On top of that, soil is a habitat for a wide variety of organisms. It houses microscopic organisms to soil fauna of larger sizes – for example, earthworms, springtails, burrowing rodents, etc. Soil is undeniably an extremely valuable and vital ecosystem that delivers ecosystem services, enabling life on Earth, fundamental to our survival.

So what exactly is soil? 

The Soil Science Society of America defines soil as the unconsolidated mineral or organic material present on the immediate surface of earth, serving as a natural medium for the growth of land plants. Others describe soil as layers of generally loose mineral and/or organic material that are affected by physical, chemical and biological processes at or near the planetary surface and usually hold liquids, gases, and biota (living things) and support plants. 

Composing of a mixture of minerals, water, air, organic matter, and decaying remains of living things that once lived, the components of soil fall into two distinct categories: biotic and abiotic factors. The biotic factors encompass both the living and dead – for instance plants, insects and even soil microorganisms such as archaea, fungi, algae and more. The abiotic factors on the other hand represent non-living things which include minerals, water and air. Commonly found soil minerals such as nitrogen, phosphorus and potassium are amongst the essential nutrients needed for healthy plant growth followed by calcium, magnesium and sulphur. The combination of these factors ultimately determine the properties of soil – its texture, structure, porosity, chemistry and colour. But that’s a topic for another day. 

Undoubtedly, soil builds and supports the foundation of a community, a nation, and basically any form of life. The giving nature of soil provides us and other forms of life with an abundance of resources. 

Soil can also be described as a repository of memory, holding records of the past of our planet, our evolutionary history of how far we have come. It may also store secrets and possibilities that have yet to be discovered to a sustainable future. 

Essentially, all life depends upon the soil… There can be no life without soil and no soil without life; they have evolved together.

Dr Charles E. Kellogg

So while you keep your feet on the ground, stay grounded and stop treating soil like dirt.

References

Certini, G., & Ugolini, F. C. (2013). An updated, expanded, universal definition of soil. Geoderma, 192, 378–379. https://doi.org/10.1016/j.geoderma.2012.07.008

Es, H. (2017). A New Definition of Soil. CSANews (Madison, Wis.), 62(10), 20-21. https://doi.org/10.2134/csa2017.62.1016