Soil Quality vs Soil Health

7 Oct 2010

                In applying concepts on a large scale basis, clarifying terminology is not only helpful, but vital. Vocabulary in the sciences is no different. Clear, precise definitions allow for minimum confusion and promote effective communication. It is also important to know when two terms are synonyms as opposed to similar concepts. One such example is found within soil ecology, involving the terms “soil quality” and “soil health.”

                Soil quality, simply stated, is considered to be the ability of the soil to perform its functions. While this general definition is somewhat ambiguous, Karlen et al. (1997) describes soil quality much more specifically as “the capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation.” According to this definition, a high quality soil is a high functioning soil. Such a soil would have good aggregation and sufficient pore space to allow air and water to penetrate and promote life above and below ground. High quality soil should also contain appropriate amounts of organic matter and a balanced mineral content to ensure the nutrients are available to the resident organisms. Also important is the soil texture- the distribution of charged particles, such as the negatively charged clay, can impact water retention and nutrient availability, impacting many other areas of the soil’s ecology.

                Soil health also focuses on the ability of soil to function, but it includes the idea that soils are, in a sense, living entities. According to Doran and Zeiss (2000), “soil health is the capacity of soil to function as a vital living system, within ecosystem and land-use boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and promote plant and animal health.” A healthy soil would include the same things as a high quality soil. But when considering a soil to be a healthy soil, emphasis would also placed on ensuring that the interconnected systems and processes that allow a soil to behave as it does remain intact, and that the soil supports biodiversity and species richness.

                While the terms soil quality and soil health seem nearly identical, there is one main difference that prevents the terms from being interchangeable synonyms. If a soil is high quality, there is a good chance it will be healthy, and vice versa, but not necessarily. However, soil quality includes benefitting humans, while soil health refers more to the intactness of the soil ecosystem.  Because of this, a high quality soil that is productive by human standards, either for agriculture or by providing a base for development, might not be a healthy soil due to compaction, pollution, and other factors that would limit the ability of natural cycles to function and would inhibit natural biodiversity and abundant life. While high quality soil does require organisms dwelling within it, such as bacteria, earthworms, and many others, to make it high quality, the original species biodiversity and richness probably is not the same. Good soil health, on the contrary, aims to preserve these components essential to the soil organism. Due to these differences, soil quality and soil health, while very similar terms, are not the same and should be used appropriately.

Doran, J.W., Zeiss, M.R., 2000. Soil health and sustainability: managing the biotic

                component of soil quality. Applied Soil Ecology 15, 3–11.

Karlen, D.L., M.J. Mausbach, J.W. Doran, R.G. Cline, R.F. Harris, and G.E. Schuman. 

                1997. Soil quality: A concept, definition, and framework for evaluation. Soil 

                Sci. Soc. Am. J. 61:4-10.

Soil in Modern Music

Even modern music recognizes the importance of the soil! (although they may not have all the facts straight...) The song "Worms Make Dirt" by The Aquabats, while not entirely correct (what is a chanuk anyway?), is at least entertaining:

Worms make the dirt

And the dirt makes the earth

And all of the roots have a place to sleep now

All the chanuks have squash to eat now

Worms make the dirt

And the dirt makes the earth

And people hold hands and feel terrific

Food comes from dirt

It's scientific

http://www.youtube.com/watch?v=aC1tNah8n-c

Beauty in a Forgotten Ecosystem

            When we take a step onto a perfectly manicured lawn we don’t often think about the underground world we tread upon. But beneath every step we take, whether it is in a carefully decorated garden or into the archaic beauty of a forest, lays an intricate hidden world full of life.  

One afternoon last week I had the opportunity to delve into the unknown labyrinths inhabited by soil organisms. My classmates and I each dug up two large cubes of soil- one from the forest floor, one from the neighboring field. Armed with our notebooks, pencils, and curiosity we set to work dissecting our miniature models of the soil ecosystem.

As I carefully picked through the entangled matrices of roots and decaying plant life in the forest cube, I was alerted not only to the bountiful life dwelling there, but to the beauty of nature’s artwork. The forest soil cube held many wonders. 

            A small stick with fungus growing upon it. Tiny organisms scurrying about desperately trying to avoid my prying fingers. 

          A small seed bud just beginning to blossom. Whereas normally, walking above ground, I would overlook these minute details, now, with my senses honed in to look beyond the ordinary, the scenes unraveling before me were transformed into the extraordinary. The mold on the stick was no longer just fungus, no longer just a piece of the complex web of life I was witnessing. It was also a masterpiece in and of itself. Later on, back at the lab, I was able to see under a dissecting microscope its frayed edges, the perfectly placed striations, the rich earthen colors. 

            Even a seemingly ugly piece of decayed leaf held beauty and purpose. The veins still visible, showing the vast network from a previous life, now decomposing in order to render new life in the soil.

The soil cube from the field was covered in a simple, green grass that masked the complexity beneath. The underside revealed the burrows of worms and other organisms, twisting their way through the rich soil. 

            This cube held a crowd of larger, more easily visible and recognizable organisms. I uncovered multiple earthworms as well as ants, beetles, and even a lonely cricket. 

      Looking closer at the cricket back at the lab, I was surprised by its almost symmetrical appearance and humbled by the tiny details seemingly carved onto its glistening back. Even the physical soil itself was beautiful to behold. The deep dark brown that was the body of the soil was riddled with small, lighter brown streaks. 

The two cubes of soil perfectly embodied the concept that soil is not just lifeless dirt, but a complex ecosystem brimming with life. While the forest and field cubes had their differences, they both clearly displayed the complexity of the subterranean ecosystem and the natural beauty found within it. In an interview with Kevin Stuart from the University of Hawaii in 1984, the notable soil scientist Hans Jenny declared that “if you are used to thinking of soil as dirt, which is customary in our society, you are not keyed to find beauty in it.” We do not realize how true this statement is until we take the time to experience the magnificence of the soil for ourselves. We must look beyond the dead dirt we initially see before us and probe into the diverse ecosystem overflowing with natural beauty.

A Misunderstood Resource

            Although many people regard soil as mere dirt to be used whenever and wherever necessary, it is in fact an important and widely under cherished resource. People fail to recognize the importance of soil in their day-to-day lives, and are unaware of how the soil interacts with other elements of the earth’s systems. Soil is a valuable resource for many reasons. Most predominantly, it is considered an invaluable resource for humanity because of its ability to aid in the production of vegetation, to regulate the hydrological cycle, to aid in the recycling of waste, to house organisms that produce the basics for some medicines, and to provide cultural inspirations.

            Soil provides physical support to plants in a more efficient and capable way than any means engineered by humans. While hydroponic systems, for example, can remove the need for soil, they require designed and engineered supports for the plants which not only cost a great deal more than soil, but do not last nearly as long either (Daily et al. 1997). 

Soil naturally regulates and maintains many processes that occur within it. Soil, along with the plants that place their roots in it, moderates the hydrological cycle. Changes to the soil and vegetation impact not only runoff, but can also affect subsurface water reservoirs (Daily et al. 1997). Soil is also a natural and important recycler of waste, preventing the exhaustion of essential nutrients and minerals in the soil.

The exchanges that happen in the soil are critical to resident plant life.  The negatively charged nature of soil particles, particularly clay, is a key component to making soil an important resource, because it allows for the retaining and exchange of positively charged cation nutrients, which plants can then uptake (Daily et al. 1997). These exchanges help regulate the fertility of soils, and along with soil dwelling organisms, naturally maintain nutrient levels. In hydroponics, the leading alternative to soil cultivation, there is a much narrower margin for error in the concentrations of nutrients available for growing vegetation, which if not handled correctly, can easily lead to expensive and irreversible trouble for the growing plants (Daily et al. 1997).

We rely on soil and its inhabitants more than we realize in our everyday lives. Not only does it provide the substrate in which many of our food crops are grown, but it has implications into other fields beyond agriculture. Soil is home to organisms that provide us with essential medicines, including penicillin and streptomycin, both developed from soil residents (Daily et al. 1997).

 Another of the values of soil is its cultural significance. It has worked its way into the traditions and customs of many peoples, and has found a place in artwork and even tourism, as people admire the landscapes formed by unique soils.

            Soil, although often overlooked as a valuable resource, is extremely important because of its ability to regulate and maintain water and nutrients, and because of its cultural impacts. It not only is a less expensive, more reasonable, and more natural way to cultivate vegetation, it is a natural recycler and houses many organisms important to these natural cycles. Because it provides so many irreplaceable ecosystem services, soil is a resource to be greatly valued and cherished.

Daily, G.C., P.A. Matson, and P.M. Vitousek. 1997. Ecosystem services supplied by soil. Pages 113-132 in G. Daily, editor. Nature's Services: Societal Dependence on Natural Ecosystems. Island Press, Washington, D.C.