No-Till Soil vs Tilled Soil a Novel Experiment

No-Till Soil vs Tilled Soil a Novel Experiment

Here’s an interesting experiment designed to show the differences in microbial activity in no-till soil versus tilled soil. While the experiment was not designed to get detailed information, it does have the effect of showing that no-till soil has higher microbial activity than tilled soil.

The experiment was designed as more of a demonstration and used mens cotton briefs, yes underwear. Since the briefs are made of cotton, soil bacteria would be expected to degrade the briefs. In no-till soil the briefs degrade over during the time of the experiment. In the till soil, the briefs did not.

The full article is below.

Brief Encounter

A Demonstration Using Cotton Underwear Offers Lessons On Soil Management

BY LORETTA SORENSEN P&D Correspondent

Why were cotton briefs used to bring a message to farmers at the 2016 South Dakota Soil Health Coalition’s first Soil Health School?

South Dakota State University (SDSU) Extension Soils Field Specialist Anthony Bly says it was an effective way to draw attention to the way different soil management practices affect soil health. A pair of briefs was buried in the soil at three different locations that included corn with conventional tillage, soybeans under mulch tillage and no-till soil where cover crops are grown.

“Crop diversity in itself causes soil microbial populations to rise and fall,” Bly says. “That’s because the crops play a role in feeding the microbes. Moisture conditions also play an important role in soil microbial populations.”

After selecting the sites, briefs were buried to about the waistline five weeks before he needed them for his demonstration. Cotton briefs were used because cotton contains carbon, which is one of the things soil microbes feed on.

“Men’s cotton underwear briefs contain high amounts of carbon,” Bly says. “Therefore, they can be buried in the soil and retrieved to observe and evaluate soil microbiological activity and ultimately soil health status.”

In the soil health demonstration, a new pair of briefs was compared to the brief from each field. The brief buried in the no-till field where cover crops were grown showed the most deterioration. As part of the evaluation of the project, the briefs were weighed to make a statistical comparison of the deterioration of each pair. The control brief, which was never buried, weighed 58.5 grams. The brief buried in the conventional tilled corn field weighed 50.8 grams. The briefs buried in the mulch till soybean field weighted 48.3 pounds. The lightest brief was the one buried in the no-till soil, weighing 28.4 grams.

“Hardly anything was left of the brief that was buried in the no-till soil,” Bly says. “That indicates extensive soil microbiological activity and a blanced soil ecosystem. That’s the kind of soil microbiological activity that will cause crop residue to quickly break down.”

Bly points out that he isn’t a soil health researcher but is familiar with soil health principles. He explains that soil health researchers sometimes use the idea of a “herd” to explain how soil microbes function.

“If you think of the microbes as a herd of cows, it’s easier to understand how diversity boosts soil microbiological activity,” Bly says. “The ‘herd,’ when they have the same crop every year or are in an environment where two crops are consistently rotated every two years, microbiology diversity decreases. That’s because the mono crops or just the two crops provide food for a certain set of microbes. Ten different plants would provide resources for a wider range of microbiology.”

Different plants also provide different levels and combinations of carbon and nitrogen, so a wider range of plants will stimulate a wider range of soil microbiological activity.

The briefs project wasn’t intended to provide a great deal of scientific information. Since the fields where the briefs were buried were random, and there was way to establish a control site, the conclusions of Bly’s project were fairly simple.

“Since there was less of the material left from the briefs buried in the no-till site we concluded that microbial activity in that field was greater there than in the other two sites,” Bly says. “That information may be helpful to no-tillers who struggle with lack of residue breakdown. Adding cover crops or diversifying their crop rotation may boost soil microbial activity and break residue down more effectively.”

Bly also believes no-tillers might benefit from understanding the value of diversified cropping in terms of soil health. While no-tillers realize some benefit from no-till practices, they may be able to significantly increase those benefits with added crop diversity.

“Keeping a live root in the soil with cover crops is also key to active soil microbiology,” Bly says. “Roots exude carbohydrates, which is one of the foods microbes want. Microbes bring nutrients to the plants and consume the carbohydrates, creating a synergy that can improve plant and soil health.”

Soil microbes also form soil aggregates, which are groups of soil particles that bind to each other more strongly than to adjacent particles. The space between the aggregates provide pore space for retention and exchange of air and water.

Cover crops also sequester inorganic nutrients such as nitrates that remain after a crop is removed. Instead of migrating into waterways, the unused nutrients can be held in the soil for use at a future date.

“Many people have seen the rainfall infiltration demonstration which explains the importance of soil health, too,” Bly says. “Many times people have an ‘Aha!’ moment when they see that demonstration and more thoroughly understand how important it is to promote and support soil health. We hope some folks who saw the briefs demonstration had the same kind of realization, which can be a really great moment.”

Bly also notes that research is demonstrating that soil microbial activity and soil health can further be enhanced with a crop/livestock integrated system that helps utilize and manage plant residue levels.

Additional information about soil health and the importance of soil microbiology can be found at www.nrcs.usda.gov, searching for “The Living Soil: Bacteria.”


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