By Dusty Sonnenberg, CCA, Field Leader, a project of the Ohio Soybean Council and soybean check-off.
It has been said the more we learn the less we know. That seems true when it comes to our soil biology. Danielle Kusner is a certified crop advisor and Terrain Advocate for Deep Soil LLC.
“Transitioning from what we traditionally study in soil chemistry and the elements, to soil biology is a higher level of understanding of soil systems,” Kusner said. “We are at a revolutionary time in agriculture. Understanding soil microbes and biology will change what we do on our farms.”
Kusner said studying the soil food web helps farmers realize that the more they learn about the soil, the less they find that they know.
“The soil food web is comprised of multiple levels,” Kusner said.
The first level is made up of photosynthesizers. It contains the plants shoots and roots. The second level is made up of decomposing mutualists, such as pathogens, parasites, and root feeders (bacteria, fungi, and nematodes). The third level contains shredders, predators, and grazers. These would include arthropods, nematodes that feed on fungi and bacteria, and protozoa. The fourth level is made up of still higher-level predators such as more arthropods and nematodes. The fifth and final level is comprised of even higher-level predators such as animals and birds.
“A historical study of soil biology traces back to the two main groups; fungi and bacteria,” Kusner said. “Lichens are an example of the relationship between fungi and algae. They are a complex life form that is a symbiotic relation between the two. They are neither a plant nor an animal. The fungi provide a structure for the algae to live in. The algae provide food for the fungus.”
Understanding this relationship helps when trying to understand the relationship between Mycorrhizal fungi and plant roots.
“Plants make up 80% of the mass on earth. More than 90% of all plants depend on Mycorrhizal fungi (MF),” said Kusner. “The term Mycorrhizal fungi comes from the Greek fords for fungus (mykes) and root (rhiza). Mycorrhizal fungi make up one third to one half of the living mass of all soils.
“Mycorrhizal fungi act like metabolic wizards. They serve as chemical transformers and decomposers. They transform some of the toughest compounds on Earth, such as rocks and wood into plant usable nutrients. They have the ability to explore, scavenge and salvage.”
A study has found that 80% of a plant’s productivity is connected to the bioavailability of essential nutrients. When Mycorrhizal fungi are present, soil respiration increases, soil structure improves, and the Mycorrhizal hyphae help hold water. Crops can compete with weeds and diseases better, and drought resistance improves.
Mycorrhizal fungi can provide up to 100% of a plant’s phosphorus needs and 80% of the nitrogen needs. Mycorrhizal fungi move nutrients from high concentrated areas to low concentrated areas.
“Mycorrhizal fungi hyphae extend two to three feet around a plant,” Kusner said. “In an organic system, the Mycorrhizal fungi will mine, search, and convert nutrients for the crops. The mycelium send nutrients to the plant roots.”
In the Rhizophagy Cycle, microbes enter the plant root cell periplasmic spaces carrying nutrients from the soil. The nutrients are then extracted from the microbes by reactive oxygen produced by NOX on the root cell plasma membrane. After that occurs, the microbes exit through the root hairs depleted of the nutrients. While exiting, the microbes stimulate elongation of the root hairs and exit at the tips of the hairs where the walls are thin. Once they are outside the root back in the rhizosphere, the microbes reform cell walls and recharge with nutrients, and the cycle repeats.