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Soil Biology Important at Planting
by LuAnn Rolling, District Conservationist
Since we are in the middle of the planting season, I wanted to discuss the importance of soil biology to an emerging plant. Soil with good biology will include bacteria, fungi and other microscopic organisms. If a plant emerges in soil that does not have good biology it will send roots out searching for it, which could take 10-14 days. If there is good biology in the soil, the plant would begin to immediately absorb nutrients generated from the biology and put that energy towards growth and reproduction.

According to John Kempf, a top expert in the field of biological and regenerative farming, the yield potential for corn - in terms of determining how many rows of kernels and how many kernels per row - is determined during the first two weeks of a corn plants’ growth. Biological root colonization in the first 14 days determines the ability to absorb nutrients throughout the entire growing season.

Kempf states that there is a difference between synthetic fertilizer and the type of fertilizer that is provided by soil biology. For synthetic fertilizer to be absorbed by a plant there must be free water in the soil profile. He adds that biological nutrients can be absorbed by the plant in the absence of free water, so even in very dry conditions the plant can continue to absorb nutrients created by biology.

According to P. Lavelle and A. Spain in their book Soil Ecology, 90% of the nutrients taken up by plant roots are cycled through a soil organism before becoming plant available. A corn plant that utilizes nitrate from synthetic fertilizer must use up to 16% of the energy created from photosynthesis to break the nitrate absorbed from synthetic sources into amino acids and proteins that it can use.

Kempf states that natural nutrients created from soil biology are available immediately to the plant and are therefore not an energy “drain”.  He says that since the plant has excess energy it stores it in the form of lipids. Kempf explains that these excess lipids are then sent back into the soil through the roots. Bacteria cannot digest lipids but fungi can. The plant has just stimulated fungal growth. Fungal populations create true organic matter that will be present in the soil.

Some producers wonder why they make management changes that do not produce an increase in organic matter in their soils. This is because continued use of high fertilizer rates cause the natural plant/soil interactions to be suppressed so even though there may be plenty of plant residue there will never be organic matter increases. According to Neil Sass, NE Iowa Area Agronomist for the NRCS, “organisms like earthworms, fungi, protozoa, and bacteria are part of the soil food web. This soil food web cycles plant residues through various soil organisms and creates nutrients that are ready for plant uptake, as well as creating more stable forms of soil carbon that are food for fungi and go towards increasing carbon stocks in the soil”

In a March, 2021 article in No-Till Farmer, Kansas farmer Josh Lloyd says, “I quit spending all my money on grid sampling, fertilizer, and lime. My dollar is best spent growing something. Always growing something. Photosynthesis is the only way to get carbon out of the atmosphere and into my soils where it can be put to good use. That’s why I keep a living root in my soils 100% of the year when possible.”

Lloyd adds, “Carbon is on the rise in my soils. I can see it when my shovel turns over rich, dark, living earth where just a decade before there was only lifeless, tan clay. This progress has been achieved through my combined use of no-till, cover crops, planting into green cover, double cropping, carbon-conscious crop rotations and the addition of livestock.”