soil life

The Living, the Dead, and the Very Dead

Joelle Neff 2023, Uncategorized , , , , , , , , ,
Soil needs microbes, dead plant and animal matter, and carbon to become healthy. Compost is organic matter. Roots add to organic matter.

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

Earthworms and other soil life are important for oranic matter and soil health.

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:

  1. Mix organic matter into mineral soil
  2. Stabilize soil aggregates and structure
  3. Make new chemicals and new cells in the soil

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

Plant residues from corn and other plants lend to healthy soil and organic matter.

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:

  1. Main source of food for soil organisms
  2. Provide nutrients for living plants
  3. Improve soil structure

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

Decomposed plant materials make up the topsoil.

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:

  1. Slowly release nutrients to plants
  2. Protect plants from harmful chemicals
  3. Reduce compaction
  4. Improve water retention

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.

Resources

Magdoff, F., & Van Es, H. (2021). Building Soils for Better Crops: Ecological Management for Healthy Soils (Fourth Edition). Sustainable Agriculture Research and Education (SARE).

Life in the Soil

Joelle Neff 2021, Quarter 4 , , , , , , , , , , ,
Life in the Soil

There’s so much that happens below the surface of the soil. There is an entire ecosystem within the rich earth that we grow crops, grass, and trees in. Below are just a few examples of the diverse life that can be found beneath the surface.

Earthworms: Earthworms are “nature’s tillers”. They eat their way through the soil making burrows which increase water infiltration and make room for plant roots to reach deep into the soil. Poop might be gross, but earthworm poop adds a lot of good bacteria, organic matter, and nutrients that plants can use right away into the soil. Tillage is the biggest “bad guy” when it comes to earthworms, and certain fertilizers and insecticides can greatly harm these beneficial animals.

Ants: Ants are arthropods which means they are animals that have a hard exoskeleton. You can find ants all over the world. They form large colonies that make their homes underground. These nests and the tunnels that connect to them allow increased air and water movement throughout the soil. Ant nests also make microbes happy which results in more available nitrogen.

Protozoa: Protozoa are microscopic, but they are still bigger than bacteria, protozoa’s main source of food. Protozoa can impact the amount of organic matter and nutrients available to plants by how much bacteria they eat. Protozoa can take on several shapes. Some are amoebas which move by getting big and then small again. Some have little waving hairs called ciliates, and some move with a flagellum which spins like a whip or a tail.

Nematodes: Nematodes are microscopic worms that live in tiny air and water filled pore spaces in the soil. They eat all kinds of things like fungi, bacteria, algae, other nematodes, protozoa, and insect larvae. Some types of nematodes feed on plant roots which can harm crop growth. Even though some species of nematodes are pests, others are not, and they actually help the release of nitrogen that the plant can easily use. Some species even prey on harmful insect pests.

Fungi: There are at least 1 million fungal species present in the soil. Mushrooms are a type of fungi. They do a really good job of breaking down dead plants and animals which put nutrients into the soil. Fungi helps to stabilize the soil structure and is good at cycling nutrients.

Grubs: Grubs are beetle larvae, meaning they’re baby beetles. Grubs are worm-like, and they live in the soil. They can be anywhere from ¼ inch to 1 inch long with bodies curved in a “C” shape. Grubs feed on plant roots which can greatly stunt the plants growth. They also eat seeds and seedlings which can keep plants from growing.

Ground nesting bees and wasps: Some bees and wasps live inside the soil by making burrows. One example of a ground nesting wasp in a Cicada Killer. These large wasps can be 2 inches long. They dig burrows into the soil that can be 12-18 inches long and 1 ½ inches wide. Cicada Killers paralyze cicadas and lay eggs on them to feed their larvae. These insects do not colonize, but Cicada Killers will often burrow near each other. The males cannot sting, and the females will only sting if they are mishandled.

Annual Cicadas: Cicadas spend their adult lives above ground, but they spend their time as nymphs in the soil. Cicadas lay their eggs in tree branches. When the eggs hatch, the nymphs fall to the ground where they burrow into the soil and feed on plant roots. This can cause damage to young trees and plants. After two years of living in the soil, the nymphs, which look like adult cicadas but without the wings, will emerge from the soil and molt to become a fully formed cicada.

Mole Crickets: Mole crickets have large front legs that they use for digging. Much of their life is spent in the soil. Mole crickets hatch as nymphs, looking very similar to adults, and they dig around in the soil looking for food. Although they spend some of their adult life outside of the soil, they return to the ground in winter. These insects’ tunneling can cause a lot of damage to turf grass, but they can also increase soil aeration and infiltration.

Moles: Moles are insectivores, and they can grow from 5 to 7 inches long. They spend most of their lives in the soil. They have small eyes and ears that are protected by fur. Underground, they don’t have much need for eyesight. They have large claws which help them dig through the soil. Moles can benefit the soil by increasing aeration and infiltration. They help organic matter to travel deeper into the soil, and for subsoil material to move closer to the surface bringing nutrients along with it. Although they can add benefits to the soil, many homeowners find moles a nuisance.

Resources:

Brady, N. C., & Weil, R. R. (2010). Elements of the nature and properties of soil (3rd ed.). Upper Saddle River: Pearson.

https://extension.entm.purdue.edu/fieldcropsipm/insects/soybean-white-grubs.php

https://extension.entm.purdue.edu/publications/E-63/E-63.html

https://content.ces.ncsu.edu/periodical-cicada

https://extension.psu.edu/moles#:~:text=Moles%20play%20a%20beneficial%20role%20in%20the%20management,%28organic%20matter%29%20to%20travel%20deeper%20into%20the%20soil.

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