LOUISVILLE, KY – What you can’t see won’t hurt you, goes the old adage. Not so. There is a lot going on underground in your fields that could be hurting yields. That was the message of Ken Ferrie, Crop-Tech Consulting and Farm Journal field agronomist. He laid out his findings over a five-year field study on soil density and its effect on root systems to his audience at the National Farm Machinery Show.
His presentation, “Roots for Higher Yields” looked at how changes in soil density in the soil profile impacts the configuration of roots, especially corn roots, in both the A Horizon and deeper B Horizon.
“If the soil is too dense or has collapsed through compaction or lack of moisture, roots trying to go deeper will be like a fly hitting a screen door,” Ferrie said to make his point. In corn, he puts a great deal of importance on what happens to the first and second crown roots as they penetrate below the 4-inch level in soils. Will they encounter a horizontal tillage level of resistance?
“Farmers need to know why this is so important. We have learned that the first and second crown roots are determining ear size—well underground,” Ferrie teaches. “Then the third crown root and where it is able to go maybe the most important of all—it is these roots which carry the moisture to plants during the growing season. Are they shallow? Deep? Forced to move sideways instead of spread into lower soil profiles? Critical questions. These three root patterns are high-dollar roots.”
The 4 and 5 crown roots are generally more for support and achoring the plant, sometimes above ground (brace roots). They are less of afactor on yield than crown roots 1, 2,and 3.
Ideally, Ferrie has learned, “roots need to be able to go anywhere they want to, and not be forced because of density to go sideways. They need to be able to penetrate 1-2 inches into the B Horizon. It roots can get through (the soil) so can water.”
He refers to the 3rd crown root system as “weather proofing for the corn plant.”
His five-year soil density study in central Illinois soils (1996-2000 seasons) has caused him concern about the impact spring tillage practices may be having on the crop—negatively. “I would say 85% of the compaction I have seen was caused by the first pass in the spring.” That pass is likely creating a horizontal layer at some depth below the soil surface which then creates a challenge for roots to penetrate.
Ferrie has been studying a combination of ways to (deep) till in the fall, followed by a less punitive first-pass in the spring with a tillage tool such as the chopper harrow. His objective is to create an A Horizon that is uniform in density to the 7-11 inch fall tillage to open up soils at the 14-17 inch depth.
“There is clearly a bushel cost with corn if a horizontal level is there in the soil profile, regardless of how it got there,” Ferrie explains. “For corn; not much of a factor with soybeans.”
He adds, “We expect to see damage done by spring rains, if there are roots caught in an oxygen-depleted zone. A dense horizontal layer may prevent rain from soaking deep, resulting in ponding either on the surface or in the top soil region, especially in the higher clay content soils. If roots can’t negotiate through the soil, neither can excess moisture.”
