Organic matter makes up 1-6% of most soils. Organic matter (OM) is what makes your soil fertile. Soil biology can live and thrive in OM and so can your plants. Organic matter is derived from decomposed plant and animal materials, which supplies nutrients for organisms. It also forms different sized aggregates that aid in better gas and water exchanges in the soil. So, what makes up organic matter? OM is made up of three parts: the living, the dead, and the very dead.
The “living” part of organic matter is made up of the organisms that call soil their home. Bacteria, fungi, viruses, algae, moles, rabbits, woodchucks, plant roots, etc. are all considered living organic matter. Soil organisms make up 25% of the earth’s total biodiversity. In just a teaspoon of soil, there are tens of thousands of different organisms. Soil organisms have 3 main roles:
Microorganisms, earthworms, and insects feed on plant residues and manures for energy and nutrition. In the process, they mix OM into the mineral soil. Earthworms have a sticky substance on their skin that helps bind soil particles together. Other materials produced by fungi have a similar effect. These aggregates make up good soil structure. Roots and other organisms produce channels that stabilize soil structure and help with water infiltration. The sun puts energy into plants through photosynthesis. This energy ends up in the residue of plants after they die which microorganisms break down to create new chemical compounds.
The “dead” part of organic matter is made up of the fresh residues including dead microorganisms and earthworms, old plant roots, crop residues, recently added manures, etc. Fresh residues have 3 main roles:
Soil organisms eat the dead organic matter for energy, breaking it down which releases the nutrients necessary for plant growth. As the living organisms decompose the dead material, they release chemical compounds that bind soil particles together and benefit soil structure.
Some residues are broken down by soil organisms more easily than others. Proteins, amino acids, sugars, and starches are broken down very easily. While lignin, which is a fibrous compound, takes much longer for organisms to break down.
The Very Dead
The “very dead” part of organic matter is made up of substances in the soil that have already been decomposed by soil organisms and are inaccessible for further breakdown. We refer to this as humus. Humus has 4 main functions:
Humus has a good Cation Exchange Capacity (CEC) and has the ability to bind to nutrients that are essential for plants. It slowly releases these nutrients for plants to utilize while reducing the risk of leaching. Some humus molecules can encase potentially harmful chemical compounds in order to protect plants from taking them up. Humus can rebound and prevent compaction problems while also reducing soil density, improving aggregation to hold onto and release water when necessary.
What do we learn from soil organic matter?
Organic matter is extremely important for nutrient availability for crops, soil structure, and water retention. Disturbing soil has effects on the living, the dead, and the very dead parts of organic matter. Tillage destroys the habitat of living soil organisms and aggregates of soil structure. It can also make humus (organic matter that is inaccessible for further breakdown) more accessible to soil organisms for decomposition, releasing carbon into the atmosphere.
Converting your growing operation to a no-till system is easily manageable and can even save you time and money! To learn more about growing no-till click here.
Magdoff, F., & Van Es, H. (2021). Building Soils for Better Crops: Ecological Management for Healthy Soils (Fourth Edition). Sustainable Agriculture Research and Education (SARE).
Mike Werling is a fourth generation farmer in Decatur, Indiana. Farming is his lifestyle. He started with his father and now its in his blood. Mike started on his journey of soil health and conservation farming because he hated seeing erosion on his fields.
As a part time employee with the Allen County Soil and Water Conservation District (SWCD), Mike has learned that it’s hard for people to change their attitudes, and this lends to challenges in educating other farmers to adopt conservation practices. This does not altar Werling’s determination, though.
Some practices Mike incorporates are cover crops, no-till, grass waterways, water and sediment control basins, buffer strips around his upland areas, and drainage water management.
Werling’s motivation is to leave his soil better than how he found it. Enjoy the full interview with Mike Werling!
Where does your food come from? Many students across Indiana give the answer “the grocery store.” Although this is often true, the grocery store is not the starting place of our food. Farm Bureau’s Agriculture in the Classroom Program works with kids around Indiana teaching them about the origins of their food and why farmers are important. Through this program, Farm Bureau holds summer workshops for teachers and volunteers giving them ideas about how to teach agriculture in their hometown school systems.
The Allen County Soil and Water Conservation District had the opportunity to participate and lead a couple of sessions in one of the Agriculture in the Classroom workshops on June 1st at Huntington University. Mike Werling, a farmer and part time employee with the Allen County SWCD, lead a workshop on managing erosion. Erosion is a menace that has plagued agriculture for millennia. Werling used the slake test, a homemade rainfall simulator, and a purchased rainfall simulator to demonstrate different ways teachers can educate about soil health and erosion control in their own classroom.
The slake test shows the structural difference between soil in a no-till situation and soil in a tillage situation. It utilizes two class cylinders filled with water. Mesh wiring drapes like a hammock from the top of the cylinders and submerges in the water. For this demonstration, you must have two different dried peds of soil. One ped should be from a no-till field and the other from a tilled field. When the aggregates are submerged into the water and placed on the mesh wiring, the audience can see the difference between the tilled soil and the soil from a no-till field. The no-till ped will hold together, but the soil from the tilled field will break apart easily in the cylinder. Check out this video of a slake test!
The homemade rainfall simulator can be made out of 3 plastic, two-liter bottles with 1/3 of the plastic cut out of the side. One of the bottles should contain nothing but bare soil. The second bottle should be filled with soil, but covered with residue like straw, leaves, or sticks. The third bottle should contain growing cover crops (clover, annual rye, cereal rye, oats, etc). Water is then poured over the two-liter bottles. The bottle with bare soil will lose the largest amount of soil to erosion, the soil with a residue will lose significantly less soil because of the residue, and the cover crop soil will lose the least amount of soil when “rain” is introduced to it. Check out this video of a two-liter bottle simulator!
The purchased rainfall simulator works very similarly to the homemade version. Watch this video to see how a rainfall simulator works!
The Allen SWCD also shared a lesson on watersheds and water quality. Joelle Neff used an Enviroscape to teach about how water moves downhill and picks up pollutants in a watershed. Neff also taught a lesson called “Growing with Water” which uses data collected from the Water Quality Initiative Program to discuss why pollutants have varying impacts at different times in the year.
An Enviroscape is a model of a watershed landscape that funnels water into the landscape’s reservoir. The model has a farm, factory, nature preserve, golf course, construction site, neighborhood, water treatment facility, roads, and ditches. Pollutants such as fertilizers, pesticides, human and animal waste, oil, road salt, etc are introduced to the landscape. Simulated rain is then applied to the landscape. Students are able to see all the pollutants that have entered the reservoir after the rain. This tool has fairly easy clean up. You can remove the plug in the reservoir to drain water into the basin below.
Like mentioned earlier, “Growing with Water” uses data collected from the Fort Wayne Water Quality Initiative Program which has been collecting water samples weekly in Northeast Indiana and Northwest Ohio since 2002. Check with your local Soil and Water Conservation District (SWCD) to see if collect water samples in your area. “Growing with Water” teaches students about the quality of water in their area and the different pollutants that can impact their water systems. Growing with Water shows the variances of water quality in different seasons. Split your class into three different groups: spring, summer, and fall. Have each group come up with a list of what is happening in agriculture and with the weather in their season. Then, provide students a tracking sheet with the percentage of time that the pollutants were higher than they should have been. Have the students work in their groups to make hypotheses about reasoning for the pollutant levels based off what is happening in their season.
If you would like to use any of these demonstrations to teach in your classroom, give the Allen County SWCD a call at 260-484-5848 ext. 3.
Derek Thompson, a Noble County Farmer and NRCS District Conservationist, shared about life on the farm and the return on investment of incorporating conservation practices onto his operation in an interview with the Allen County Soil and Water Conservation District.
Thompson is a third generation farmer of a 1,000-acre grain and dairy farm. His family’s conservation journey started in the ’70s when his father tried out a no-till corn planter from the Noble County SWCD. Although not lead adopters, the Thompson family now incorporates no-till and VRT soil management into all their acreage because of their return on investment, time savings, and the pride that comes with restoring the soil and the land. Their other conservation practices include sidedressing nitrogen, buffers along ditches, grass waterways, cover crops, and planting green.
Although being a District Conservationist with the Natural Resource Conservation Service (NRCS) has played a role in the farm’s conservation journey, Thompson believes they would have still ended up exactly where they are even without his involvement with NRCS.
Watch the full interview below!