ST. CLOUD, Minn. – Soil health is one of those things growers know they should be looking at, but don’t always know how to. At this year’s Conservation Tillage Conference (CTC), the topic of soil health was thoroughly discussed – how to observe it, how to measure it and how to improve it through reduced tillage and increased cover.
“There's a lot of pretty simple and easily attainable tools you can use and methods you can learn that will tell you just about everything you need to know when it comes to soil health,” said Stan Boltz, NRCS soil health specialist.
Boltz was a presenter at the CTC and demonstrated the different methods and indicators used to determine soil health.
The first step in evaluating soil health is to simply dig a hole.
“The shovel is the best tool. By just digging a hole you can start to observe things in the soil,” Boltz said. “On farmland, digging down 12-16 inches is plenty. You get down to 12 inches in most cases, and that's going to tell you everything you need to know.”
Soil health is something that can change very quickly depending on management practices for better or worse, so it is important to regularly look at the soil and see where it is at as far as health is concerned.
The color of the soil is important. Farmers should be comparing that color to what has historically been the color of the soil in that field, as well as to what the color should be for the soil type.
The structure of the soil is also important to look at once the hole is dug and how the structure changes throughout the profile. Growers will also want to look for any compaction layers – where are they and how thick the layers are.
Soil structure and compaction lead to water infiltration. During the CTC, Boltz explained and demonstrated how a water infiltration test can be done.
“Infiltration, as we found out over time, looking at dynamic soil properties, is very sensitive,” he said. “There can be fairly high variability when you do the test, but if you're taking enough samples, you can get a good representative number.”
The test is easy enough to do and test kits are available through the NRSC and other sources.
An aluminum ring, six inches in diameter and five inches high, is pushed into the soil until about 2-2.5 inches remains above the ground. The ring is filled with about an inch of water and the amount of time it takes for the water to absorb into the soil completely is measured.
The faster the water flows into the soil, the better the infiltration.
“It's a surrogate measure of habitat and porosity for soil organisms. Porosity is very difficult to measure from a scientific standpoint,” he said. “Infiltration is a good surrogate measure of that, aggregates, and a whole bunch of things that combine together to give you that infiltration number.”
Soil-born microorganisms have a huge role to play in infiltration and soil health. They are also essential for nutrient cycling and plant health.
Those microbes are also easily impacted by management practices, especially tillage practices.
“That soil is the habitat for those critters. If you think of your own house, you take a steel shank the size of a telephone pole and run it through your house – that's going to be quite disturbing,” Boltz said. “If it doesn’t outright kill them, they're going to spend all their time and energy rebuilding the house.”
Instead of making connections throughout the soil, you’re providing nutrients to plants and improving plant health.
Another thing that happens when soil is disturbed is a great deal of carbon dioxide gets released.
“You get a boost initially from tillage in the growth of your plants, but you also release a lot of that carbon and then that food source is gone for the plants and critters living in the ground,” he said. “It's pretty rough on the things living there if you're constantly turning things upside down.”
The NRCS recently released the new in-field soil health assessment pamphlet, a guide growers can use to measure and observe their soil health. It discusses ways to measure soil organism populations, measure soil resistance to penetration, and more.
“It has a lot of good ideas on things to look for in the soil,” he said. “There's a whole slew of ideas on things to look for when you're doing an in-field, hands-on assessment of the soil health in your fields.”