Once upon a time there were two farms a mile apart. Both had the same silty clay loam and silt loam soils. Both used a corn/soybean rotation and no-till practices. However, Farm A had been no-tilled for three decades and Farm B for only two years (prior to that, it was farmed using horizontal tillage). The big difference: Farm A’s corn yields were 70 bu. to 75 bu. per acre more than Farm B.
When Farm Journal Field Agronomist Ken Ferrie set out to address the yield discrepancy in 2011, he found it was in part linked to poor soil health.
“Improving soil health means sustaining productivity and profitability, not just for ourselves but for future generations,” Ferrie says. “It requires a systems approach because healthy soil involves many components.”
The components fall into the following three categories:
- Physical (soil texture, aggregate stability, available water capacity, surface and subsurface hardness and infiltration rate).
- Chemical (nutrient and pH analysis from a soil test).
- Biological (organic matter).
To set Farm B on the path to better health, Ferrie used several tools and tests to identify problem areas (see ”Soil Health Toolbox” on page 26). Chief among his concerns were surface and subsurface compaction, soil acidity, low biological activity and low nitrogen-supplying power.
Start With The Easy Problems
Soil density and acidity are among the easiest soil health issues to fix, so that’s where Ferrie and the farm operator concentrated initial efforts.
“We deep-tilled to fix subsurface compaction and remove dense layers, and we chisel-plowed to break surface compaction and mix in limestone,” Ferrie says. “Over three years, we converted the field to a vertical format, free of sudden density changes and soil compaction, by using vertical tillage. The operator was then able to put the field back into a no-till system for the most part.”
To correct acidity and help fix structural problems, lime was applied in the fall for three years and incorporated with fall vertical tillage. As a result, pH values increased from the 4.9-to-5.2 range to the 5.8-to-6.4 range following the lime applications.
Vertical tillage and liming work together to fix structural problems. “When a field gets extremely acid, it destroys structure and stops water infiltration,” Ferrie says. “When we apply lime, we are attempting to flush out the acidity. If we have poor infiltration, we can’t get water into the soil to make the lime work.“
Aggressive vertical tillage, to mix in limestone and improve water and air infiltration, and correcting soil pH increased Farm B’s corn yields to within 20 bu. to 30 bu. per acre of Farm A’s yields in three seasons. The yield improvement was enough to make the farm profitable.
Using Cornell’s Comprehensive Assessment of Soil Health, Farm B’s silty clay loam rose from 48.3 to 59. The silt loam score climbed from 40.4 to 47 (out of 100).
Then Address The Hard Parts
Encouraged by the progress, Ferrie and Farm B’s operator focused on improving the chemical and biological aspects of the soil.
That’s where cover crops come in — with a goal of diversifying soil microbes; improving soil aggregation, water filtration and storage; suppressing weeds; reducing soil erosion; and recycling crop nutrients so they won’t escape.
“Because the soil was acid for so long, and subjected to too much tillage, much of Farm B’s soil structure has been destroyed,” Ferrie says. “We can’t fix structure with a single treatment — although the lime we’ve applied helped because the calcium flocculates clay particles (while the carbonate corrects acidity).”
Poor structure causes soil particles to run together and seal. That leads to erosion and surface crusting, which causes stand problems.
“While corn’s grassy roots might help build soil structure, the soybeans in the rotation don’t help much,” Ferrie says. “We realized we had to add wheat or a grass cover crop for continued improvement.”
Flying annual ryegrass seed into soybeans in 2015 sounded promising; but, for reasons not fully understood, the cover crop failed to establish.
That fall, the farmer harvested some corn early and drilled cereal rye into the stalks. “The timely seeding produced a good stand,” Ferrie says. In the spring, he no-tilled soybeans into the cereal rye.
In the more productive silty clay loam, the cover crop had no effect on yield. But in the less productive silt loam soil there was a bushel or two yield increase.
The 2016 yield increase was not enough to pay for the cost of the cover crop, Ferrie notes. “But at least it wasn’t a yield drag,” he adds.
Analyze the Results
Attempting to explain the yield effect, Ferrie ran several soil health tests. The results for the water-soluble (ortho) phosphorus and aggregate stability tests provided a clue.
“Water-soluble phosphorus is a pretty good indicator of biological health,” Ferrie says. “The increase from 1 ppm to 2 ppm in some locations is significant.”
Under the cover crop, the aggregate stability score moved in the right direction with a slight increase. “Eventually, improvements in aggregate stability should result in improved water infiltration and other areas such as the soil’s carbon/nitrogen ratio,” Ferrie says.
For the past three years, Farm B’s operator has continued to evaluate cover crops in plots across the 400-acre field.
”The days of deep tillage are history,” Ferrie says. ”The soybeans are no-tilling well, but the operator continues to struggle with crusting issues when planting corn, so we’re still experimenting with cover crops in conjunction with no-till, strip-till and spring vertical till,” Ferrie says.
Because he was aware of his soil’s low nitrogen-supplying capacity, the farm operator also implemented variable-rate fertility to make sure the crop never ran short.
“He applied nitrogen in his dry fertilizer, weed-and-feed treatment and in-starter fertilizer at planting,” Ferrie says. “He sidedressed the rest, using soil nitrate tests to determine what rate to apply.”
Yield Gap Narrows
Gradual improvements in soil health has led to gradual improvements in yield. From 2017 to 2019, the yield gap between the two farms has steadily closed. In 2019, Farm B’s corn yields ranged from 240 bu. to 270 bu. per acre, which is still 10 bu. to 15 bu. per acre behind the other field. However, the soybean yield is within 5 bu. per acre.
”We’re making headway with Farm B’s soil health. Using the rain simulator, we know water infiltration has improved,” Ferrie says. ”The field’s pH is more balanced.”
Healthier soils create a more sustainable farm for future generations.
“That’s the goal we have to keep in mind as we invest time, money and effort in improving soil health. It will be worth the effort,” Ferrie says.
What Ken Ferrie Wants You to Know
- Improvements in soil health can be documented in just a few years, enough to move yields from unprofitable to profitable.
- The fastest improvements involve fertility and pH (the chemical aspect of soil health) and eliminating compaction (the physical aspect).
- Improvements in the biological aspect of soil health take longer.
Soil Health Toolbox
Through the years, Ken Ferrie has used the following tests and tools to evaluate soil health:
- Soil pits.
- Visual field observations.
- Penetrometer: measures soil hardness, or compaction.
- Gempler’s Soil Test Kit.
- Slake Test: measures how well soil holds it structure.
- Cornell University Sprinkle Infiltrometer: simulates rainfall onto the soil surface; an accessory kit measures the infiltration rate of water.
- Carbon dioxide meters or Draeger tubes: measures soil respiration.
- Air dried clods in a jar of water: evaluates soil structure.
- Soil Biological Respiration and Nitrification test (BRAN): measures carbon dioxide respiration by soil microbes, which is fueled by the active carbon portion of the organic matter in the soil (available from Midwest Laboratories).
- The Soil Heath Tool: uses factors such as carbon dioxide respiration rate, active carbon and water-soluble carbon as indicators of the soil's nutrient-supplying power (developed by USDA-ARS and available at a handful of labs).
To learn more about the chemical, physical and biological components to improve the health of your soils, visit AgWeb.com/soil-health
Read the 2019 America's Conservation Ag Movement Annual Report in Farm Journal.