Farmers utilize a variety of tools to evaluate soil health

RICHMOND, Ill. — Focusing on soil health is important for farmers since soil fertility is not inexhaustible.

“Soil health is the continued capacity of the soil to function as a living ecosystem that sustains plants, animals and humans,” said Brenna Ness, working lands ecologist for the McHenry County Conservation District.

“When we manage soil health, we’re maximizing water storage and infiltration, improving carbon capture and storage, increasing biological function and diversity and reducing erosion,” said Ness during a presentation at the Women Farmland Stewards Learning Circle, hosted by The Land Conservancy of McHenry County and the American Farmland Trust.

Farmers can use informal and formal methods to measure soil health.

“An informal way is to look at your fields after a rainstorm to see if the water is infiltrating or sitting on top,” Ness said. “You can dig in the soil with a shovel to look for earthworms.”

A bottomless coffee can be used to measure infiltration.

“Add a known volume of water and keep track of how long it takes for the water to fully drain,” Ness said. “You can bury a cotton cloth in the soil to gauge the microbial activity by how much the cloth decomposes after a few weeks.”

The slake test will provide farmers an idea of the soil structure and the aggregate stability.

“This will show you how well your soil structure will hold together when it is saturated with water,” Ness said. “The longer it takes the soil to break down in water the more stable the soil aggregates are to be able to resist erosion from rain or wind.”

For the slake test, wire mesh is placed into a clear jar to suspend the soil sample.

“Then you add water and wait five minutes to see how much of the soil is left sitting in the wire mesh,” Ness said.

Using a penetrometer to measure compaction is a formal method for measuring soil health.

“The gauge tells you how much pressure it takes to push it into the soil,” the ecologist said. “From zero to 200 PSI is green, 200 to 300 PSI is yellow and over 300 PSI is red.”

Ness assesses the compaction at 6, 12 and 18 inches in the fields that are in the district’s Farm Program, which totals 6,850 acres and involves 70 producers.

In addition to cropland, the program includes grassland for hay production, grassland for grazing and conservation areas.

For lab tests to measure soil health, Ness likes to use the Haney test which is done by a laboratory in Kearney, Nebraska.

“It costs $65 per sample, but I like the Haney test because it tells you the soil organic matter, the soil respiration rate and a soil health score,” Ness said.

“The soil respiration ranges from zero to 1,000 ppm of carbon dioxide which tells you if your soil is alive or dead,” she said.

Other measurements include water extractable organic carbon and water extractable organic nitrogen.

“These are indicators of how much food is available to microbes in the soil,” Ness said.

“The water extractable organic carbon and nitrogen and the respiration rate are taken into consideration to create the soil health score,” she said. “That score can range from zero to 50 and most farms don’t score over 30.”

Ness talked about two soil tests from 2021 and 2023 that were from samples taken from the same field.

“What’s interesting about this field is it had been in row crops for decades and in 2021 we did a high-density prairie seeding,” the ecologist said.

“In 2023, we found the organic matter went from 2.5% to almost 5% and the soil respiration multiplied by five from 63 ppm to 316 ppm,” she said. “The soil health score went from 9 to 29.”

In the fall of 2024, bison started grazing this field.

“We’re going to test the soil again to see how the bison grazing impacts the soil,” the ecologist said.

Ness highlighted the results of 89 studies that evaluated the impacts of farming practices on water infiltration.

“The studies found cover crops were very impactful and increased infiltration on average by 35%,” Ness said.

“Perennial ground cover next to croplands like field borders increased infiltration on average by 59%,” she said. “If there were all perennial covers like hayfields or pastures, that increased infiltration by 89%.”

Four years of data collection from the district’s farms shows fields with permanent cover have the highest levels of biological activity.

“That’s not really surprising,” Ness said. “But the cropped land that has also had cover crops, the soil respiration and worm counts are bumped up to almost in line with the perennial cover.”