Soil health versus soil tilth: What’s the difference and why do they matter to farmers?

Feb 17, 2023 | How it works

Soil health and tilth

“Dirt,” one soil science professor used to tell their new classes of science undergrads, “is just bits of soil out of place. Soil is much more than what’s on your shoes and what you can see.”

Soil does not equal dirt. Soil teems with diverse life. Insects and microbes like fungi, nematodes and bacteria call soil their home and work together under the ground in ways we don’t fully understand. As a result, soil is integral to sustaining life.

Soil health is critical to food production. Plants need sunlight, water, air and nutrients from the soil to grow. A deficiency in any one of these can stunt plant growth. And when we’re talking about agriculture, deficiencies mean poorer crop production. Unfortunately, conventional farming methods can be hard on soil health, but some guiding principles and best management practices can help maintain or improve soil health and tilth.

Wait, what’s soil tilth? Basically, soil tilth refers to how suitable soil is for growing crops. It’s just as important as soil health, and just like soil health, it all comes back to those tiny yet mighty microbes.

Why growers should care about soil health and tilth

Doug Kremer is a scientist and the CEO of ag tech company TerraMax. He focuses on harnessing naturally occurring soil microbes in ways that make crops healthier and more profitable for growers. “Healthy mineral soil is 45% minerals, 5% organic matter, 25% water and 25% air,” says Kremer. “The other way to think of this is that 50% is open space. Whether it’s filled with water or air, healthy soil should be 50% open space, depending on your sand and clay content. That’s what you aim for as a farmer.”

This open space allows for healthy root development and facilitates nutrient and water transfer to the plants, which are all critical to healthy crops. In addition, healthy space in the soil allows fertilizers to work to their full potential. Good tilth means microbes in the soil have the space and resources to break down organic materials into nutritious humus that gets incorporated into the soil.

Kremer explains it using a corn field as an example. “You harvest your crop, and corn stalks lay on the ground,” he says. “This plant residue needs to degrade and integrate into the earth to generate good soil.”

If there’s no available space in the soil for this process, soil health will decline.


5 principles of healthy soil

According to the USDA, there are five principles of soil health.

  1. Soil armor, like cover crops, prevents erosion, weed growth and keeps the soil from getting too hot, among other benefits.
  2. Minimizing soil disturbances such as overgrazing, over applying chemical and physical disturbances.
  3. Plant diversity instead of monocultures.
  4. Continual live plant/root where cover crops fill in during the dormant times and continue nurturing the soil food web.
  5. Livestock integration harnesses the synergistic relationship of animals and plants that boosts resiliency.

A top obstacle to healthy soil

So then, what’s the enemy of healthy, loose soils? Compaction, or the loss of that 50% ideal open space due to compression. Unfortunately, compaction is relatively unavoidable. “You’re not going to get away from soil compaction,” Kremer says. “If you have an acre that you tend by hand, you will still compact the soil.” Walking on the soil will compact it. Even rain can compact soil, which ties into soil health principle No. 1, as cover crops can shield soil from the hard impacts of rain.”

So some soil compaction is unavoidable when your operations include machines like combines, despite farmers’ best efforts. If it’s raining, a farmer might encounter a situation where they start losing yield if they don’t go get their crop. “But if the soil is wet,” Kremer says, “the trade-off is harvesting the crop or damage to the soil.”


How to encourage soil health and tilth

No one solution will improve soil health and tilth, especially if your soils experience high levels of compaction. But there are some things you can do to help your soil tilth and, therefore, health.

  1. Avoid driving on wet soil.
  2. Encourage microbial activity.
  3. Be mindful of your nitrogen application, and don’t over-apply. (Certain nitrogen forms contribute to compaction.)

TerraMax has microbial inoculants that help crops like corn and soy fix nitrogen more efficiently and effectively at their roots, reducing the need for applied nitrogen. These naturally occurring microbes support robust root growth and healthy soil bacteria populations. And they are proven to increase ROI. But, as with everything TerraMax does, it must benefit the farmer. So their products can be incorporated into management practices to support soil tilth and health.