"In those years where we have very large rainfall events, these products are superior," Genrich says. "In years where we don't have any, the results are comparable."
Not losing nutrients to leaching means growers can achieve their yield goals using less fertilizer. Trials with Agrium Inc.'s ESN Smart Nitrogen controlled-release fertilizer produced a bushel of corn with a 0.5 pound of nitrogen, compared with the 1.2 pounds per bushel recommended for fine soils, he says.
Nitrate leaching is also a concern in Florida's sandy soils, where a state water management program offers some cost-sharing to potato growers who adopt best management practices, says Chad Hutchinson, a UF assistant professor of horticultural sciences.
"We've been very successful," Hutchinson says.
Controlled-release fertilizers can cut nitrogen application rates from the 200 pounds per acre suggested in the BMPsitself already lower than the local average of 250 pounds per acreto 150 pounds per acre. "That's a huge savings," he says.
Putting pencil to paper
The final equation shows controlled-release fertilizers roughly equivalent to or slightly more expensive than conventional fertilizers, Hutchinson says.
Using Scotts' PotatoBlen product, for example, might run an extra $10 to $15 per acre.
Controlled-release fertilizers provide growers with a sense of security that their fertilizer program is safe no matter how much rain falls, Hutchinson says. With conventional fertilizers, soil tests can pinpoint nutrient levels and how much fertilizer remains, but often too late to correct any shortfall.
And for crops where uneven growing conditions produce stress that creates quality defects, the steady release of nutrients can pay off in more valuable harvests, he says.
In corn and other grain crops, doling out nitrogen in a steady stream reduces the unwanted vegetative growth that can appear with sudden, large nutrient bursts from conventional fertilizers, Genrich says.
Even growth means better quality
For potato growers, evening out growth spurts should decrease such quality defects as hollow heart and internal heat necrosis, Hutchinson says.
Revels says his fields in the controlled-release tests have produced fewer defects as well as more uniformly sized potatoes--both important factors for processing markets.
"That's one of the first things I noticed in the first year," he says.