Like beauty, soil is more than skin deep. Looking at what’s going on across the field and under the soil surface provides a lot of great information about soil health.
There are a number of easy tests to do throughout the growing season to learn more about the health of soil. While standard soil tests provide valuable information, farmers can also conduct a number of cheap or free tests themselves to learn more about their fields.
“Farmers can just walk out on their landscape and look at some of these things themselves,” said Sharon Weyers, soil scientist with USDA in Morris, Minn.
A widely-published scientist who works with many soil scientists and other staff, Weyer’s focus is on nutrient cycling and turnover from the microbial perspective.
She is constantly working on ways to provide farmers and the general public with better knowledge of soil health.
“There’s something living underground,” she said. “That’s really my main goal – to get people to think about it. It’s not dead. There’s something living underground.”
One test for microbial activity is a soil respiration burst test (called the Solvita CO2 Burst test) that costs about $15 per sample.
A soil sample is taken down to 6 or 12 inches below the soil surface and sent to a participating soil testing lab.
According to Solvita.com, soil is moistened with a relative volume of water, triggering a flush or “burst” of carbon dioxide. This expresses the soil’s microbial potential under disturbance conditions and is the test of choice for soil regions experiencing intermittent strong dry/wet cycles. The magnitude of the burst is quantified with the Solvita Digital Color Reader.
“If you have a high amount of CO2, you have a lot of microbes in the soil that are doing a lot of things. If you have low CO2, you don’t have a lot of soil biological activity,” said Weyers, who often visits farmers and others to help interpret these test results. “If your CO2 burst test is showing an increase (of microbial activity) over time, then you’re doing something positive.”
Soil science testing
As a scientist, Weyers measures microbial biomass carbon and nitrogen using the Chloroform Fumigation Direct Extraction procedure. Although this method has been around since 1987, it has never been adopted by commercial test labs.
The process uses duplicate samples of soil to compare the results. A potassium sulfate salt solution is applied to one soil sample to extract soluble carbon and nitrogen. The other soil sample is placed in a desiccator with chloroform that causes the microbial cells to open up and spill their gut contents that are extracted with the salt solution and measured.
Between the initial potassium sulfate measurement and the fumigated sample, there is an increase in the amount of carbon and nitrogen. That increase is associated with the amount of microbial biomass in the soil.
Easy tests for biological activity
There are also some fun tests that farmers and families can do to learn more about what’s going on in the soil.
- Weyers encourages farmers to take a clod of soil and put it in a clear container (like a pint or quart jar) with some clean water. “If it holds together, you’re doing pretty good,” she said.
- Using the senses tells a lot about the land. First, getting out to the farm field, what do you hear? Are there song birds singing? They will be eating insects and grubs. Simply holding some soil in your hand and smelling it tells you something too. It should smell green and alive, she said. Visually, you want to see worms and worm holes and insects like ants or beetles as signs of healthy soil.
- Another simple test can determine how well your soil drains water. Cut off both ends of an empty coffee canister and push the can down into the soil. Add water. If the water ponds and drains slowly, then you don’t have much aeration in your system. “You can look at this whether it’s your garden, your front yard or out in your field,” Weyers said.
By visiting farm fields every couple of weeks throughout the growing season, it’s easier to keep track of what is going on as far as the soil health. Weyers always encourages people to look for what’s going on beneath the surface.
“You want to be able to do that in your cropping system, or in your tree grove, or just sit in your backyard and go, ‘Wow, you know there’s life here.’ If we connect with our landscapes, we’re going to treat our landscapes better,” she said. “We’re going to find ways to feel for it.”