Did you know that December 5 is celebrated around the globe as World Soil Day? Join us as we journey into the vast, incredibly important world of soils, and how it affects us and the health of the San Antonio River watershed!
What is Soil?
What is soil, if not just ‘dirt’? Soil may be more complex than most people realize! Soil is typically described as about 50% mineral and organic matter, 25% water, and 25% air. But if you dig deeper, there are so many variations and combinations of those few things that result in so many types of soils—clay, sand, and loam (a mixture of sand and silt) being the key categories.
Healthy soils are crucial to life, much in the same way that water is—in fact, it’s all connected!
But what do we mean by “healthy soil”? Can soil be unhealthy? Just like the water in the river, there are many things that can impact the quality of soil systems. This can cause imbalances or degradations and affect the services these systems provide. Healthy soil provides us with our food, provides important ecological benefits like storing carbon, reducing flood risk, and improving water quality, and is a major contributor to biodiversity.
This above infographic aims to raise awareness of soil biodiversity as a nature-based solution. “Don’t say ‘dirt’ when talking about soil! ‘Dirt’ is what you get on your clothes and in your car, but ‘soil’ is where it’s supposed to be and sustains life!” Image Credit: FAO
Soil’s Secret Recipe: The Natural Cycle of Nutrients
Soil is an important part of nutrient cycling: a process where nutrients move through the air, the rain, and, of course, the soil! It’s no secret that plants require nutrients to grow and produce their flowers and fruit, nuts, or other forms of seeds. Nitrogen, phosphorous, and potassium, also shortened to N-P-K, are the most frequently mentioned nutrients as they are the main ingredients of fertilizers.
Like fertilizers, leaves and other sources of organic matter provide these nutrients slowly and naturally to soil systems. Plants can utilize these nutrients to feed people and wildlife. However, healthy soils also have living components like microbes (e.g. bacteria and fungi) and a variety of insects and invertebrates that can be degraded by the regular addition of fertilizers.
The Link between Soil and River Health
When soils are healthy, they may also provide benefits to surface water quality and quantity! All soils contain air and water, but they are structured in particular ways that also allow water to be absorbed and held temporarily. When it rains on degraded soils, there may be less infiltration and more erosion.
Image Credit: FAO
Healthy soils are not compacted and can allow water to infiltrate and move into the soil. Though water may still run off in heavy storms, healthier soils are more likely to aid in the reduction of floodwaters, especially with the assistance of native plant communities. This can also lead to improved water quality, because as water runs overland, especially bare, unhealthy soils, more particles may be picked up and carried to the stream, impacting water quality. Keep in mind that many soil types and combinations exist, and not all soils exhibit the same exact qualities!
If you’ve noticed some parched-looking areas around your plants and home, consider using nature’s free mulch—fallen leaves!
Leaves can be a good buffer to help retain soil moisture and over time, they break down to recycle their nutrients back into the soil!
The Biodiverse World of Soil
Soil nutrients can come from multiple sources, but they’re often distributed by animals! Did you know that approximately 59% of all species on earth live in the soil?! Many of these are microscopic but also include some insects and mammals, and all of them play a role in the health of the world below our feet! Let’s highlight two really cool soil critters that we may not think about in relation to healthy soil: ants and fireflies!
There are many subterranean (underground) organisms, but perhaps none are as ubiquitous as ants! While ants are often regarded as pests due to their abilities to swarm, bite, or sting, ants are incredibly important for helping to cycle nutrients into and throughout the soil! Ants also help to aerate soils and move nutrients from decaying matter underground.
Red Harvester Ants (pictured above) are an important native species that helps to keep soil healthy.
Fireflies also have a strong connection to the soil. These ephemeral (short-lived) wonders that flash during summer nights typically spend their long larval stage underground or in the leaf litter above ground. The larvae depend on healthy soils that can retain enough moisture and can provide other small surface or subterranean animals like snails and worms for them to eat.
All firefly species live within the soil surface during their larval stage. They are soil invertebrates! (Photo: Katja Schulz, iNaturalist (CC-BY))
Healthy soil is the foundation of life, supporting ecosystems, water quality, and biodiversity while sustaining our food systems. This World Soil Day let’s celebrate the incredible world beneath our feet and take steps (pun intended) to protect and nurture it for generations to come!
To learn more, check out these resources!
Learn more about Texas Soils from the USDA’s Natural Resources Conservation Service
Learn more about Soil and Invertebrates from the Xerces Society
Learn more about World Soil Day from Food and Agriculture Organization of the United Nations (FAO)
Check out the USDA’s Web Soil Survey, which has maps and data for almost 95% of the nation’s soil!
