Soil, schmoil… what do we need to know about soil?
Marla Mertz, Marion County Conservation, and Linette Bernard, Feathers & Ink
Iowa and much of the Corn Belt is known for deep, productive soil. Although often taken for granted (particularly by those who are not directly dependent), soil will always play a role in our lives. Soil is what we dig in as children, plant our gardens in, and where the vast majority of the world’s foodstuff is grown.
The soil we have took millions of years of action and addition of organic matter to be what we have today – deep, black, humus-rich topsoil. The humus is the key ingredient, made from decaying plants and animals, which allow our soil to hold water like a sponge and nutrients like the cupboard shelf!
Try this: Take the family outside your house and help your children look for signs of where the water flows when it rains. Ask them to predict where the water goes. Take pictures of any signs of erosion in and around your yard. During the next rain shower, go outside again to verify or disprove the family's predictions about where the water flows. Brainstorm about ways to minimize erosion on your property. Explore with your family where the water goes downstream and if there is a relationship between the water drainage on your property and where water drains in your neighborhood or community. Discuss the term 'watershed' (the area that drains into a particular river or lake).
- USGS Streamer Map -- You can trace a stream upstream or downstream! A great visual tool that shows a watershed.
The topsoil is the uppermost layer of the soil. If you could dig down DEEP you could see the topsoil, subsoil, and the parent material. Soil scientists call this the soil profile. Each layer may be inches thick or feet thick. Knowing the soil profile is important to farmers and builders as some layers of soil are impermeable to roots and water. Some soil layers can be unstable and others too shallow. All soil grows from the bottom parent material. The soil profile is a record of what has happened to the soil in that area. (Graphic at right courtesy Iowa Conservation Education Coalition.)
- Topsoil is the top layer where life is most abundant. You’ll find plant roots, bacteria, fungi, and small animals.
- Subsoil has fewer living organisms that topsoil and is generally harder when dry and stickier when wet that soil above (topsoil) or below (parent material).
- Parent material has even less living organisms that the two layers above and gets the name because its rock material is the same as most of the soil above it.
Try this: Collect soil samples in jars or bags from several different areas like a garden, a field, the woods, an empty lot, near water. Mark each sample as you collect! Gather a quart jar for each sample. When several samples are collected, spread out each sample separately on a sheet of newsprint. Crush any large lumps and remove large rocks, stick, and trash. For each sample, fill a quart jar about 1/4 full and add water until the jar is 3/4 full. Put one tablespoon of alum in each jar, put the lid on tight, mark the sample on the jar, and shake for several minutes. Let the jars stand. Predict what might happen. You will start to see the larger, course particles settle to the bottom, the finer particles of silt, clay, and loam will form the next layer, and floating on the top of the water will be the organic matter (dead leaves, twigs, stems, and parts of plants and animals). The more organic matter in the sample, the richer the soil. Talk about how long it took the samples to settle out. Why did some samples take longer to settle out? Which sample had the most organic matter? Can anything be done to improve the sample with the least organic matter?
That topsoil is what allows the agricultural economy that we have today. We can’t have one without the other.
Soil only becomes dirt under our fingernails or when we track it into the house! But what makes soil? According to Dr. Burras as noted on inhf.org, “Soil is a delicately balanced set of physical, chemical, and biological components that nurture and support root growth and provide landscape services we often take for granted. Soil simultaneously:
- holds water in a plant-available form while allowing excess water to drain,
- provides 12 essential nutrients in usable, nontoxic forms,
- permits oxygen to penetrate throughout the rooting depth while insuring carbon dioxide escapes into the atmosphere,
- stabilizes temperature so a root never overheats in the hottest summer or freezes in the coldest winter,
- serves as habitat to microorganisms, ants, worms, gophers and many other animals, and
- offers adequate strength to keep plants standing even in the worst wind storms or when a herd of buffalo passes through.”
Links for learning:
Soil grows foods and plants, but did you know that soil can also be the home for many animals. Yes, burrowing animals will make dens or nests deep in the soil, but many insects need the soil as a home, too.
Beginning late May in southern Iowa, the periodical cicada began emerging. These cicada are the 17-year cicada variety and were last seen in 1997.
“The cicadas wait a long time to reappear, and, when they do, they are synchronized to appear in mass numbers all at once. That beats any predator that would want to make a livelihood of eating periodical cicadas.”
Donald Lewis, professor of entomology, Iowa State University
See more from Iowa State University about the 2014 cicadas here.
On 2 June 2014, the 17-year cicada hatch started at Cordova Park in Marion County! Check out these photos of this hatch in a Google Photos album! The first seven photos are of the emerging nymph to the dried off adult.
Listen to the 17-year cicadas at Cordova Park on 9 June 2014!
This video tries to capture the huge number of cicadas in just one area and has a time-compressed section of a cicada emerging from the exoskeleton -- very cool!
Remember all animals, regardless of where they call ‘home’ are important to the balance of nature by pollinating plants, aerating the soil, controlling rodent populations, or even being food for others. This badger (and companion) have set up 'home' in a road ditch.
Thanks to the Iowa Natural Heritage Foundation and Mark Thompson, Red Rock Lake Association committee member, for their help with information. The 'Try this' activities were adapted from "Iowa's Soil: A Teacher's Guide to Soil Activities" from the Iowa Conservation Education Coalition. These booklets are out of print, but you may be able to find an ICEC member who still has them!