North Dakota Identifies Copper Deficiency in Some Soils

FARGO -- Feb 26/99 -- North Dakota State University researchers found sandy soils with low levels of organic matter and field contour can combine to produce a copper deficiency that reduces spring wheat yields. The NDSU study supports research in Canada that has been underway for more than a decade.

"The deficiency itself looks just like drought damage," says Dave Franzen, soil specialist with the NDSU Extension Service.

In 1998, Franzen and other NDSU researchers established six test plots, two each on undulating terrain in Benson, Barnes and Wells counties. Prior to planting spring wheat, they soil tested for micronutrients and then applied copper sulfate at a rate of 5 pounds actual copper/acre. Prior to application, all plots had soil copper readings of 0.4 to 0.5 parts per million.

"A soil test alone will not tell you if you'll get a response to a copper treatment," Franzen says. "Copper might be the perfect site-specific product to apply."

In the NDSU study, only one plot responded to the copper treatment—a 15-bushel-per-acre response. The plot responding had the sandiest soil and the lowest organic matter content, but geography also plays a role, Franzen says. Based on NDSU and Canadian research, he expects hilltops and slopes to benefit the most from copper treatments.

"Hilltops can be productive, with proper nutrients and rainfall," Franzen says.

But what is a hilltop? Any upland position within a field, whether the elevation is 6 inches or 40 feet. Franzen says, "It can be any bump."

For 1999, NDSU researchers will be establishing 10 plots across the state for the copper study and will grow spring wheat and durum. Their goal is to begin pinpointing further what agronomic and geographic conditions are most likely to produce yield responses to copper. They also plan to study what role copper may play in reducing disease, because last year wheat in some plots had reduced levels of Fusarium head blight (scab) compared to other plots.

"We don't know what that means yet," Franzen says.

Canadian research shows that copper treatments can reduce ergot infections, which first appear during flowering. Similarly, scab infects wheat plants during the flowering stage. Copper deficiency may sterilize the pollen produced by wheat plants. In order for pollenation to occur, flowers must remain open longer.

Because copper sulfate is expensive (about $4/pound of copper, applied), producers suspecting a copper deficiency and wanting to experiment should treat small strips to see if they get a response to copper. Franzen recommends experimenting only on sandy loam soils containing less than 2.5 percent organic matter and 0.6 parts per million of copper.

Franzen says organic matter serves as a reservoir for nutrients. The lower the organic matter, the fewer the reserved nutrients, including copper. Also, copper is held in clay and silt, not in the coarser materials comprising sandy soil.

"Those coarser materials just don't contain high levels of micronutrients of any kind," Franzen says.