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Compaction Limiting Yield
Farm equipment is obviously getting larger. Speed of field work is important, but at what cost to our soil does the extra horsepower, with the extra weight have? According to South Dakota State University Soils Field Specialist Anthony Bly, “Back in the day, they weren’t recommending any more than 5 tons per axle. We’ve well exceeded that in most all of our tractors and combines today.”
Bly says the weight of farm equipment is supported by the soil, and if the weight is too high or if the ground is too wet when it is worked, it can severely compact the soil. “Porosity decreases, so we have less ability to store water and nutrients - especially those mobile inorganic soil nutrients that are mostly in the soil moisture, the water.”
Tillage is another cause of compaction. Tillage breaks up soil structure and pulverizes the soil surface, creating a condition that seals the soil, resulting in more runoff. Bly noted that disking is a common practice used by road engineers to compact roadbeds so that water doesn’t enter the soil and cause damage with the freeze and thaw cycle. That’s not a goal producers should have for their fields and pastures.
In 2021, Bly co-authored a study that used x-ray scanning to compare the makeup of soil managed with different practices. The study found that soil from no-till fields managed with diversified crop rotation, cover crops, and livestock integration had 57% porosity - space for air and water infiltration - and an internal water movement rate of 4.7 inches per hour. Soil from conventionally tilled fields managed with a corn/soybean rotation, no cover crops, and no livestock integration had 49% porosity and an internal water movement rate of only 0.8 inches per hour.
Research at the UNL Rogers Memorial Farm near Lincoln showed a much greater infiltration rate for no-till, over 4 inches per hour, than for tilled conditions, only 0.4 inches per hour, after 25 years of continuous tillage system evaluation.
Producers can limit their tillage and keep livestock off wet cropland, but they are unlikely to transition to smaller equipment. The best way for them to fight compaction caused by heavy equipment, Bly said, is with living roots - cover crops and diverse crop rotations.
“Let the roots and natural biology, a plant’s biology, do that work,” he said. “Every root has some compaction fighting capability. That’s why crop rotation is important. That’s why a diverse cover crop mix is important, to have fibers and taproots and all those gradients in between.”
For producers who would like to try cover crops, Bly said that since all roots have some compaction fighting ability, it’s better to pick a diverse cover crop mix that will meet producers’ operational goals. “A living root, just period, is in my mind the important thing to focus on,” he said.
