Soil health is about how well the earth is able to function as a living environment that sustains plants, animals and humans. Soil health is altered over time by natural processes and influenced by management.
“It’s the same as watching a child grow — one day it’s in your arms, the next it’s grown as tall as you — the imperceptible change over time,” said Aaron Hird, a soil health specialist for the Natural Resources Conservation Service. “One day you’re farming a field, the next you’re farming a brick of clay and it takes more work.”
That is due to changes in the soil’s bulk density resulting in soil compaction, Hird said. The NRCS calculates soil bulk density as the dry weight of soil divided by its volume.
A common problem in Nebraska is tillage-induced, root-restrictive compaction layers, he said. The plow compacts the dirt beneath the top soil. This is called the plow pan. He describes it as a soil layer having a higher bulk density and lower total porosity than the soil directly above.
The NRCS lists the engineering standard for soil bulk density at 1.33 grams per cubic centimeter. Depending on the soil type, it can range from about 1.1 to 1.6. Soil bulk density begins to affect root growth from between 1.39 to 1.69 and restrict root growth from 1.47 to 1.8. The plow pan compacts soils from 1.78 up to 1.9.
Compacted soil means roots can’t grow as well, and restricted root growth can result in stunted growth of the entire plant. Soil compaction also negatively impacts the biology of the soil.
“Soil function is influenced by biology which is impacted by management,” Hird said. “Ninety percent of soil function is mediated by soil microbes. Supporting the biological activities can improve the function of the soil.”
Keeping track of a soil’s bulk density is just as important as other factors, he said.
“Various labs offer chemical analyses and biological analyses, but also should work on a physical analysis,” Hird said. “If the ground stops equipment, it’s going to stop roots.”
He prompts farmers to be aware of indicators. Look for soil hardness and erosion. That is a symptom of compaction — an infiltration problem, he said.
“If a farmer sees erosion, it’s a tillage-induced compaction layer more times than not,” Hird said. “You can’t see the layer where the plow compacts the soil, but you can see the results.”
Another symptom is persistent crop residue. Sometimes crop residue builds up until farmers complain that it feels as if they were “farming in straw,” he said. That is most likely due to a lack of biological activity in the top soil. The microbes that eat the residue aren’t dynamic. This is another result of compaction.
The prescription is a combination of soil management doctrines. No-tillage systems retain or sustain soil structure; biological activity regenerates soil structure. All good farming practices — no-till, cover crops, manure applications — equal a positive soil management system, Hird said.
The first step is to measure a field’s current condition. From those measurements, formulate a solution and then apply the solution. Then, re-measure.
“You can’t monitor what you don’t measure,” Hird said. “We can help provide measurements with the NRCS soil assessment worksheet.”
There is no “silver bullet,” Hird said. Each field is different and needs to be taken on a case-by-case basis. That is why it is essential to track the progress.
“It is really important to track success,” he said. “To verify it’s worth the time and effort.”
But, it will take time to see the benefits of change.
“Like exercise for the body — you can’t work out once and expect to see a difference. You need to accumulate the benefits over time,” Hird said.
For more information on how to implement soil health solutions, visit www.nrcs.usda.gov/wps/portal/nrcs/site/ne/home/.
Jon Burleson can be reached at email@example.com.