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submitted by Matthew Welsh, Resource Conservationist, Natural Resources Conservation Service (NRCS), USDA

Farming industry publications such as magazines and online content are full of advertising for seed corn, insurance, chemicals, implements and many other agricultural products. In the February 2023 issue of  Successful Farming a particular ad caught my attention. The add was a foldout page with a picture of tilled cornstalks with the caption “Your Ideal Soil Profile Starts Here”. When opening the fold out, it points to the start of an “ideal soil profile” as a tillage implement, specifically a multi tool vertical tillage implement from a well-known implement line. I think this advertisement begs two questions: What is an ideal soil profile? and what do vertical tillage machines do to the soil?

In my opinion, an ideal soil profile would begin at the surface with plant residue or other organic material protecting the surface and recycling carbon sources back into the soil. Immediately below the surface is the A horizon or top soil, consisting of a well aggregated structure, with water stable soil aggregates that are held together with the aid of organic compounds resulting from biological decomposition of organic matter. The quality soil structure present in the top soil allows for ideal air and water movement thereby developing a sufficient depth of soil that has active soil biology aiding in optimum growing conditions for plant life. The top soil is overlaying a transition horizon before a parent material from which the soil is forming.

Now that we have a general definition of an “ideal soil profile” what would a vertical tillage implement exactly do? These implement tools use gangs of coulters to cut and slice residue and operate at higher speeds than other tillage tools. Implement companies are coming up with more aggressive “vertical” tillage tools that invert soil and function more similar to a disk. Some have coulters with adjustable angles or shanks that can be raised and lowered on-the-go for variable tillage depths. This raises the risks of creating compaction zones and damaging soil structure in the top layer. In addition all of the vertical tillage implements will cut and size residue to a point that residue can easily be lost with wind and water erosion. Full width gangs of coulters slicing into the soil will break soil aggregates, causing instability and vulnerability to erosion. The destruction of soil aggregates also break the bacteria -fungal networks within the soil aggregates. These networks are critical for nutrient and water exchange from the soil to the plant.

With the idea of “creating an ideal soil profile” keep in mind the important soil functions, structure (aggregation), respiration, water cycling, microbial habitat, and nutrient exchanging. Tillage no matter how shallow and vertical it is, will damage soil structure and speed up decomposition of stable organic matter, and that shouldn’t be anyone’s ideal soil profile.