Strong connection: residue management and success in conservation tillage

Written by Jonathan Eisenthal

In corn-on-corn, harvesting residue boosts grain yields of the following corn crop across different tillage systems and nitrogen fertilizer rates, according to University of Minnesota research funded by Minnesota Corn Growers Association.

A research project, now going into its fourth year, conducted at Lamberton and Waseca, finds that removing residue provides a big boost. The average over the 2009-11 crop years at both locations is:

Disk-rip, No residue harvested: 190 bu/acre
Disk-rip, Residue harvested: 204 bu/acre

No-till, No residue harvested: 182 bu/acre
No-till, Residue harvested: 199 bu/acre

Strip-till, No residue harvested: 183 bu/acre
Strip-till, Residue harvested: 203 bu/acre

These results surprised researchers not only in the yield response to residue removal, but also in how close the different tillage systems performed in corn-on-corn when residue was removed.

“We often have challenges with plant emergence and early season growth in no-till and strip till continuous corn, but that seems to disappear when you harvest the residue,” said Jeff Coulter, an Extension agronomist with the University of Minnesota.

Coulter said residue harvest needs further examination, but it appears that it should not be an every-year practice, because of the vital organic matter that it can contribute to the fields over time. In the future, researchers could examine whether using manure in combination with residue harvest could work well as a means to maintain organic matter levels and replace the potassium and phosphorous that is removed from fields when residue is harvested.

Another surprising find, according to Coulter, was that it took more nitrogen fertilizer than expected to reach maximum yields in corn-on-corn, prompting the researchers to consider a future examination of what those optimum levels are. However, the research showed that nitrogen requirements were sometimes lower when residue was harvested. Apparently, the decomposition of the corn stalks, which are nitrogen-poor, causes the microbes feeding on them to draw nitrogen up from the soil. This temporarily limits the nitrogen available to young corn plants. Thus harvesting residue can temporarily increase available nitrogen.

“The underlying issue for this research was our thinking about what happens down the road if cellulosic ethanol and other uses for corn residue really take off,” said Coulter. “If the farmer is offered the opportunity to sell residue, how will that affect their grain yield and best practices for tillage and nitrogen? Some farmers are already harvesting a portion of their corn residue and mixing it with distillers grains for an economical and nutritious livestock ration.”

The research continues this year at both locations. Contributors to the research are Coulter, nutrient management specialist John Lamb, graduate student Aaron Sindelar, soil scientist Jeff Vetsch and scientist Steve Quiring.


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