"We’re seeing a lot of nutrient deficiencies this year," said Gene Stevens, agronomist at MU Delta Research Center in Portageville, Mo. "The biggest problem has been phosphorus deficiency in corn." Purple leaf color on plants is an indication of phosphorus deficiency, while plants with zinc deficiency have leaves with yellow stripes.
Even when phosphate and zinc have been applied and the soil is high in these elements, cool weather can prevent plants from taking them up, resulting in deficiency symptoms, Stevens said. "Some corn hybrids are more susceptible than others. They naturally turn purple easier because they don’t have the root system to take up the nutrients."
Delta Center soils scientist David Dunn said he has "received a lot of calls this year about phosphorus deficiency in corn. We also saw nitrogen and sulfur deficiencies in wheat.
"A lot of these are easily corrected if we know what the problem is," Dunn said. "Sometimes, what the producers are seeing could be herbicide injury. A cornfield with a phosphorus deficiency sometimes looks like herbicide carryover."
Stevens said Delta Center research indicates that purple corn responds to foliar phosphorus applications, but "you can only put on a small amount at one time.
"In a test at Sikeston in 1999, we increased yields 29 bushels per acre with foliar fertilizer in a cornfield showing phosphorus deficiency. The best treatment was two applications at the one-pound rate of 10-52-8 fertilizer."
A cool early spring in southeast Missouri, followed by high temperatures and another period of cold and wet, "put the plants in a kind of shock," he said. "The cotton is behind where it usually is this time of year, so it could be a problem if we have an early fall."
Some Missouri cotton producers using no-till and wheat as a cover crop also are experiencing problems this year, Stevens said. "There was a lot of wind damage to cotton last year, and wheat does well as a cover crop to protect against the wind. The problem is, the wheat sucked up the moisture.
"In dry springs, the trick is to kill the wheat soon enough so that it doesn’t use up the moisture, but not so soon that the wheat plants melt down when they are killed," he said.
Although the cotton crop still lags behind last year, "it seems to be on the mend," Dunn said. "Low crop prices and high fertilizer prices are farmers’ biggest problems."
Sources: Gene Stevens and David Dunn (573) 379-5431
Forrest Rose is a University of Missouri Extension and Ag Information Specialist.