'Tighty whities' test reveals soil health

'Tighty whities' test reveals soil health

South Dakota soil specialist says he hasn't seen a soil health demonstration as profound as this one.

How robust is the soil biological life on your farm? Find out by doing the “tighty whities” test.

“I have studied the soil for years and have never seen a demonstration as profound as this one,” says Anthony Bly, South Dakota State University Extension soils field specialist. He also farms some land near Garretson.

Here’s how to do the test: This summer, take men’s cotton underwear and bury it in the soil, leaving the waistband exposed. In as little three weeks, you can dig it up and see the effect. How much of the underwear remains reflects the level of biological activity in the soil.

HOLEY UNDERWEAR: From left to right is a brief that wasn’t buried in a field, a brief that was buried in a no-till cover crop field, a brief that was buried in a mulch-tilled soybean field and a brief from the conventionally tilled cornfield. The biological activity from organisms in the soil broke down the cotton in the underwear. When less remains, it indicates higher levels of biological activity. (Photo: SDSU)

Soil microorganisms require carbon to survive, explains Sara Berg, a SDSU Extension agronomy field specialist who also farms near Baltic. Men’s cotton underwear contains high amounts of carbon. Therefore, the underwear can be buried in the soil and retrieved later to evaluate soil microbiological activity, and ultimately, soil health.

During the South Dakota Soil Health Coalition’s first Soil Health School last year in Aberdeen, a tighty whities demonstration was conducted. Briefs were buried to about their waistlines in the soil in three different fields five weeks ahead of the event. The sites were a conventionally tilled field with corn, a mulch-till field with soybeans and a no-till field with a cover crop. The demonstration was replicated five times.

“Results were revealing to say the least,” Bly says.

Hardly anything remained of the brief buried in the no-till cover crop field, indicating extensive soil microbiological activity. The briefs from the mulch-till soybean field had more material remaining compared to the no-till/cover-cropped soil, and the briefs buried in the conventionally tilled corn had the most material remaining, which indicated the least soil microbial activity.

What can biological activity mean to your bottom line?

It’s self-made tillage, Bly says.

The higher the biological activity, the more residue the organisms will consume.

“But unlike conventional tillage that wastes carbon through stimulating microbial activity too quickly, soil microbial activity that slowly thrives on the carbon that plants exchange for nutrients increases soil carbon that enables greater water- and nutrient-holding capacity. No-till in combination with the other soil health practices offsets huge investments in high-horsepower tractors, tillage equipment and chopping corn heads, which also reduces fuel and labor expenses. Even if the yield of crops from soil with no-till and the other soil health practices and conventional till is similar, the no-till wins economically,” he says.

SDSU contributed to this article.

TAGS: Extension
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