NATURE NOTE - Number 40 March 14, 2022
Introduction:
I can’t say that I have ever had a scout get excited about soil. I may not succeed here in getting you too excited either, but let’s cover a few things that are important to know about:
Our current topic: Soils
It is a fascinating field of study and is perhaps one of the lesser understood parts of nature. Remember that soil serves to link many other nature topics. The Soil and Water Conservation Merit Badge pamphlet covers this subject in fair detail, and some of the info below may be useful for requirements for that badge.
The soil is always under us and it provides the very basis for much of the rest of life. We know it provides nutrients and anchorage for plants. It absorbs water. It can erode and wash away.
What makes up soil? First is the rock underlying the surface. If you dig down through the leaves, humus, and top soil and you will hit rock. The type of rock may determine to some extent the type of soil and the chemical makeup of that soil. However, remember that the soil you are seeing is most likely the result of erosion from rocks somewhere else that has been moved to its current location by water or wind erosion over many, perhaps thousands, of years. The gradual breakdown of rocks into soil is influenced by several factors: climate; topography; time; biological factors; and the parent rock material. Most of us have seen a plant or a tree appear to be growing directly out of a rock. That doesn’t happen. Somewhere between that plant and the rock is a small amount of soil that has accumulated from that rock wearing away or more likely soil that has blown in from other sources.
Many, many animals live in the soil. Some you can see, such as moles, earthworms (they aerate the soil) and many insects, and many you can’t see such as tiny invertebrate. Bacteria and fungi are there in huge numbers and serve critical roles in the development of soil and the nutrients in the soil. All of these are critical to the decomposing of plants that eventually become humus. This process returns assorted nutrients to the soil for use by plants. Many other trace minerals are also provided by the soil, such as zinc, manganese, iron, and copper. Soil is often classified as sandy, silt, or clay. Each of these is significantly different it its ability to hold water. Sand drains quickly depriving plants much opportunity to absorb water. Clay can become water logged and prevent plants from sending the small root hairs into the soil. Silt is sort of in between.
Scouts are aware of erosion caused by human activity such as exposing bare soil or use of poor drainage, etc. But another soil problem caused by humans is soil compaction from overuse of areas by heavy foot traffic or livestock. This is often overlooked, but easily seen in most campsites or along heavily used trails. Erosion by wind is also often overlooked as well, but tons of soil can be relocated by high winds.
Soil science is a unique specialty of chemistry, biology, hydrology and other sciences. It was less understood in the early years before more modern research focused on it, although farmers have known for centuries that you can “wear out” the soil in a rather short time. Even today, there are things that we don’t totally understand about soils and all its internal workings.
Nature Opportunities:
Scouts don’t need to know a lot about soils, other than it is important to take care of the soil and that it is critical to the proper functioning of the rest of nature, but there’s a couple of fun exercises you can do to make them more aware of soil.
Take a sample of soil from 3 or 4 different places and put each sample in a plastic bottle with a label of where it came from (near the creek, deep in the forest, etc.) Pour some of the soil from each sample through a small kitchen strainer onto white paper. Examine the filtered soil with the naked eye. Then examine it with a magnifying lens. Stir it up. What all do you see in the soil? What do you see that is left in the strainer? Note size, color, organic matter – including any living things – in each sample. Why are they different? What does this tell you about soil? Can you see the difference between sandy soil and more moist soil from deep in the forest? Then take those same samples and pour about a half cup of it into each of 3 or 4 plastic bottles. Then fill the bottle to about 2/3 full with water and shake it. How long does it take the soil to settle to the bottom? In some cases it will settle quickly, but other soil will take a long time to settle – if it does at all. Why is that? Relate this to the muddy streams you see after a big rainstorm. Also, do you see some organic things floating on top of the water, like tiny insects, twigs, pieces of leaves?
Again, maybe not the most exciting part of nature, but soil IS an important part of nature and deserves to be studied by those seeking to learn more about the world around us.
Thanks for visiting NATURE NOTES. Send your comments to me at:
Bob Garst
