Test fields also had higher yields the first year, but drier weather might have caused a drop-off in the second year, he says.
Controlled-release fertilizers are more sensitive to moisture levels because they rely on moisture and soil temperature to break down protective coatings.
Wet and dry cycles may slow or interrupt the process, Obreza says. At the same time, too much irrigation could hasten nitrogen release.
Wallace's Nitamin tests showed a 14 percent yield gain for chili peppers over conventional fertilizers, as well as a boost in marketable fruit. Processing beans also showed a 4 percent gain in desirable sizes, increasing marketable yields.
But, he says, high temperatures during the 2006 growing season reduced watermelon, cantaloupe and snap bean growth while encouraging chili pepper growth, potentially skewing yield differences.
Wallace suggests growers conduct their own trials before adopting controlled-release fertilizers to determine how much benefit their operations might see.
"Every grower will have a different reason for using or not using these types of fertilizers," he says.
Despite the higher price, Revels hasn’t ruled out the controlled-release products.
“The program has potential," Revels says. "The key is to improve the environment and still be able to farm and make a living at it."
University of FloridaControlled-release fertilizer opportunities and costs for potato production in Florida: