Chemical, physical and biological: the three components of soil health share a codependent relationship, according to research presented by Ken Ferrie of Crop Tech Consulting. Ferrie presented at the New York Corn & Soybean Growers Association’s Summer Crop Tour recently.
“Soil health is near and dear to me,” Ferrie said. “Soil health is defined as the soil’s ability to have productivity, benefit animals and benefit the environment.”
He listed chemical aspects of soil health: Extractable phosphorous, extractable potassium, calcium, magnesium, nitrogen, minor elements and soil pH. Biological elements include organic matter, derived from living organisms; active carbon, the food source of readily available carbon; and mineralizable nitrogen, which allows microbes to convert organic nitrogen to ammonium.
“Maintaining soil health is a tall order, much less improving it while making a profit,” Ferrie said. “As with everything that we use, it will start to show wear. Once we get past balanced fertility … the options get tougher.”
Measuring soil health includes looking at the depth of the topsoil, balancing nutrients and providing drainage.
“The quickest way to improve soil health is drainage,” Ferrie said. “We improve soil health better with drainage than cover crops.”
Healthy soil offers holding capacity, good tilth, resistance against adverse events and a strongly diverse microbiome. It’s also free of toxins. By contrast, Ferrie said, unhealthy soil has poor tilth, compaction crusting, disease, poor infiltration, poor drainage and unbalanced fertility.
Improving soil health starts with learning the characteristics of soil, including the texture and percent of sand, silt and clay. With proper aggregate stability, it “has the ability to withstand water and stay in a crumb texture,” Ferrie said. “It maintains pore space.”
Most farmers focus on soil fertility as the most important aspect of soil related to yield; however, Ferrie said that “soil fertility isn’t as tied to high yields as much as drainage. Good, healthy soil can take a lot of nitrogen because the soil isn’t producing it for you. Healthy soil has an odor you can pick up on.”
Although the soil composition can’t be changed, farmers can improve the soil health.
Crop rotation is another key to improving soil health; however, “sometimes, crop rotations don’t fit the operation,” Ferrie said.
Farmers who don’t raise livestock, have no market for other crops, have no place to store other crops and cannot profit by rotating are understandably reluctant to commit to rotating.
A proponent of no-till management, Ferrie said that some soil is “too sick” to use this management. But improving the soil health first and then and using cover crops can enable a farm to manage with no-till. This management “recycles nutrients, keeping them in the field,” he said.
“The financial ROI on cover crops is tough,” Ferrie admitted. “There’s also the true ROI: the stewardship. They are willing to break even or take a slight hit because they see the long-term benefits. I’ve heard of people doubling yield in four years with cover crops.”
He added that cover crops used along with reduced tillage help provide diversity for microbes, build soil aggregation, improve water infiltration and storage, suppress weeds and slow erosion. Cover crops can also help with erosion control and offer winter grazing and spring forage.
“The most profitable farms may not be the healthiest; the healthiest farms may not be the most profitable,” Ferrie said. “Healthy, profitable farms are sustainable.”
To keep a farm’s soil healthy, “it’s not one thing you do,” he said. “You have to take a systems approach.” Farmers will also need patience.
“The physical/biological aspects of soil health are the hardest to manipulate,” Ferrie said.
On some farms, he has observed 20-year layers in the soil, as it has become deeply compacted. “Your last pass before no-till cannot be horizontal but vertical,” he said. Otherwise, water will not penetrate the soil because it lacks a crumb structure. It also lacks calcium.
Infiltration tests can help farmers measure soil structure. The ability for more than eight inches of water to infiltrate in an hour is good.
“Usually, a grass crop can build a microaggregate,” Ferrie said. “You can use aggressive tillage or knocking apart with limestone.”
Although plowing can fix the aggregate strength, it won’t fix clumping. “The wrong tillage at the wrong time can reverse everything,” Ferrie said. “Corn can bring back the crumb, but not like grass crops.”
Acidic soil causes a plethora of problems, like poor nutrient uptake, Ferrie said. “It can cause iron and aluminum to become toxic, herbicide problems and decreased organic matter and water holding capacity.”
He advised measuring active acidity (water pH) to tell what the plants and microbes see when it comes to pH. To measure this, farmers need to know the soil textural class first.
While improving soil health, farmers should also obtain repeatable soil tests, both in the lab and in the field, to monitor the progression of their project.