Two years of research sponsored by Helena Chemical Company has demonstrated it is possible to spoon-feed fertilizers to cotton with positive yield results.
“After two years of field evaluations at 16 locations across the Cotton Belt, we are very comfortable saying the portable electrode-based Cardy Meter is a valuable tool for assessing the nitrogen and potassium status of the cotton plants, and cotton does respond positively to foliar applications of CoRoN,” says Michael Kenty, nutritional product specialist for Helena.
“We increased yields with foliar applications of CoRoN as much as 100 pounds per acre more than urea in some of our tests.”
Initiated in 2001 and continued in 2002, the Helena Beltwide Fertility Management Project involved obtaining an instant petiole analysis of N and K status of the cotton crop with a portable Cardy Meter. If deficiencies occurred, foliar applications of nutrients were made to supplement the early-season, soil-applied fertilizer application.
Helena contracted with independent researchers and university researchers at 16 locations across the U.S. Cotton Belt to test the program.
At each location, two-thirds of that state's recommended N rate was applied preplant, or at side-dress, depending on local practices. At pinhead square stage, Cardy Meters were used for petiole N and K concentration determinations. The analyses were continued weekly through cutout.
When a deficiency was detected, foliar applications of N and K were made to supplement the crop. If N was deficient, two N sources — CoRoN 25-0-0 and urea — were foliar-applied for comparison purposes.
CoRoN, a true liquid N, comes in several formulations and can be applied to many crops. The material is a controlled-release form of N with resinous qualities that adheres to the leaf.
If N and K were deficient in the petiole, a formulation of CoRoN 10-0-10 0.5 percent B was foliar-applied.
Averaged across all locations, cotton that received foliar applications of CoRoN responded more positively with yield increases than did cotton that received applications of generic urea.
“CoRoN is a non-drying material that will stay moist for several days and not crystallize on the leaf like urea,” says Kenty. “Plants absorb and store the N in CoRoN and then use it as needed over a multi-week period, allowing the full benefit of the rate applied.”
Merritt Holman, a crop consultant and private researcher in Arkansas, participated in the Helena project the past two years. He says the work has helped prove to him that Cardy Meters are accurate and reliable.
“The Cardy Meter is another tool I can use to assay a field and determine quickly if that field needs more nutrients,” Holman says.
Applying only two-thirds the recommended amount of N preplant and then foliar-feeding cotton has also caught Holman's attention.
“I've thought we have been overapplying N on our cotton crop at preplant. With the high price of fertilizer this year, it is even more important to make efficient use of every pound of N applied,” he says. “It's good to know that if we do reduce our preplant rates, we can come back with foliar applications to feed the crop.”
Holman says CoRoN outperformed generic urea in his tests.
“I was pretty amazed by how well CoRoN did compared to urea,” he says. “When you look at it on a N basis, we were applying less N with the CoRoN than with the urea, but somehow the CoRoN makes it more available to the cotton plants. It looked as though we were getting better utilization from the N applied with CoRoN.”
“The thing that stands out to me is that the Cardy Meters were well-correlated to lab results,” says David Dunn, supervisor of the University of Missouri Delta Center Soils Testing Lab.
For the second year, petiole samples from eight of the 16 test sites were tested at the University of Arkansas Plant Analysis Lab in Marianna to test the accuracy of the Cardy Meters. Petioles from each treatment were sent in weekly through cutout as a comparison to the weekly Cardy Meter readings. There was a positive correlation between the readings from the Cardy Meters and the lab results, says Kenty.
“Looking at the data over two years, we are comfortable that if properly calculated, the Cardy Meter is a useful tool for monitoring N and K levels in cotton,” he says. “They can give you a quick snapshot of the nutrient status in the crop, and they are faster than mailing petiole samples off to a lab for testing and waiting for the results.”
Dunn agrees that Cardy Meters offer a good way to get a handle on the nutritional status of cotton plants during the season. They were easy to use and fairly robust, he says.
“Using the Cardy Meters, we were able to detect nutrient deficiencies and apply foliar fertilizers appropriately.
“The Helena products were better at raising the yield, but we were never able to get the yields up to the level of the plot that received 100 percent of the recommended fertilizer rates preplant.”
Even so, says Dunn, there is real value to managing a cotton crop in this fashion.
“We know that we can detect and address a nutritional need during the season with Cardy Meters and products like CoRoN,” he says.
There is a big push by the EPA to reduce the nation's overall nitrogen usage, says Dunn. The government is going to have more and more control in the rates and amounts of fertilizers farmers can use. These regulations are coming fast, he says.
“The government has in place programs that farmers can sign up for that say you can apply up to the state-recommended amount of N, but you cannot go over unless you prove a real need and obtain a variance from the NRCS,” says Dunn.
The use of tools such as Cardy Meters and foliar nutrient products such as CoRoN could help farmers with stiffer regulations regarding fertilizer usage, he adds.
“In two years of testing this fertility management program, we have learned that a gallon of CoRoN 10-0-10 0.5 percent B at first bloom signals the plants that additional nutrients are available, helping prevent the cotton from shedding fruit,” says Kenty. “Continue monitoring the crop's N and K needs weekly by pulling petiole samples and apply additional CoRoN as needed.”
If things fall into place just right and a farmer's cotton has a good yield potential, he can use the Helena fertility management protocol to decide whether or not to make additional foliar applications of nutrients. With this system, says Kenty, a farmer could manage fertility in each individual field or farm unit separately and more precisely.