By ROBERT WAGGENER
University of Wyoming research shows that converting from mono-cropped corn to a rotation system has a significant positive impact on soil quality.
Reduced tillage, the addition of manure and planting of alfalfa as a rotation crop add to the positive effects, says Jay Norton, soil fertility specialist in the College of Agriculture and Natural Resources.
Some of the studies were conducted in southeast Wyoming fields that had been in continuous corn production with heavy tillage and traditional fertilizer treatments for six years.
• Rotating crops dramatically increases soil’s organic matter, nitrogen, carbon.
• Reducing tillage and adding manure also helps improve soil.
• Researchers discover that the benefits can be realized in a short period.
Within three years of crop rotations, Norton says, “We noticed more organic matter, more nitrogen and carbon in the soil, increased diversity in crop residue and a wider variety of microbial substrates.” These substrates provide food for microbes, and the microbes, in turn, form symbiotic relationships with crops, which improve uptake of water and nutrients.
Research focused on both forage production and cash crops.
The cash-crop study included:
• conventional rotation from dry beans to corn to sugarbeet and back to corn
• reduced tillage under the same rotation
• an organically managed alfalfa-alfalfa-corn-dry bean rotation
“At the end of four years, the total number of soil microbes increased in all three systems, with the largest increase in the organic system,” Norton says. “The most striking increases were among fungal species that break down crop residues, with five- to eightfold increases.”
Norton says that many conventional farmers have avoided the USDA’s National Organic Program because of the increased regulatory burden it brings, but they could still benefit by implementing some of the practices.
“Our research shows that organic and reduced tillage utilizing compost and minimizing soil disturbance improves soil quality — and profits — even if not implemented as strict organic or no-till practices,” he says.
For example, no-tilling corn into a 3-year-old alfalfa-grass stand maintained soil quality accrued under forage. Additionally, crop rotation improved soil quality in all production systems, whether conventional, no-till, reduced-till or organic.
Tilling a field promotes rapid loss of soil organic matter, nitrogen and carbon, while negatively impacting microbial activity.
“You can reverse this by reducing soil disturbance and adding organic matter,” says Norton, adding that his team’s research also showed the dramatic effects of composted manure application vs. synthetic fertilizers. Both can provide similar nutrients, but compost releases these nutrients more slowly, and it also builds valuable organic matter.
More studies back theory
Norton says similar studies have driven these points home in agricultural areas with highly fertile soils and better growing climates, such as the Midwest, but research has lacked elsewhere.
“We have shown that in a relatively short time period, crop rotation, reduced tillage and the addition of compost can really have an impact in places like northwest Wyoming and the High Plains [which includes southeast Wyoming],” he says. “More and more farmers I visit with are becoming very aware of soil quality and everything that comes with it.”
Another study led by UW Department of Plant Sciences assistant professor Urszula Norton reveals that soils under long-term no-till management were resilient to a single summer tillage operation. Frequently tilled soils, however, lost soil organic matter, carbon and nitrogen.
More details about these studies and others, along with contact information, are in the 2014 Wyoming Agricultural Experiment Station Field Days Bulletin at uwyo.edu/uwexpstn.
This article published in the March, 2015 edition of WESTERN FARMER-STOCKMAN.
All rights reserved. Copyright Farm Progress Cos. 2015.