Controlled-Release Fertilizer Performs Well in N.Y. Potato Trials

Reduced nitrogen leaching on Long Island is critical to conserving local water.

Published online: Mar 15, 2019 Articles, Fertilizer, Irrigation
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Source: American Agriculturist

For Long Island potato grower Allan Zilnicki, using controlled-release nitrogen fertilizer on 20 acres of his Riverhead, N.Y., farm represents an intangible benefit well worth the cost.

“It’s the right thing to do,” says the third-generation farmer. Zilnicki’s family has grown potatoes on the North Fork of Long Island for more than 80 years. He wholesales and sells his potatoes in 5-pound bags at the Hunts Point Market.

Water quality conservation is critical on Long Island, as a sole-source aquifer system is its main freshwater drinking supply.

Slow-release products decrease the risk of nutrient leaching into surface and groundwater while encouraging increased uptake efficiency by crops. A polymer coating encases a nitrogen core that releases slowly over time as soil temperature increases to trigger the diffusion.

“Water liquefies the core and through temperature-controlled diffusion, the urea is metered out into the soil over 90 days or so,” according to Sandra Menasha, vegetable and potato specialist for Cornell Cooperative Extension of Suffolk County. “The coating thickness can be adjusted to increase or decrease the number of days to 90 percent nitrogen release.”

Results on the farm

Use of controlled-release nitrogen has received mixed reviews on whether it boosts crop yield.

“The controlled-release nitrogen worked the same as conventional fertilizer for the pounds of potatoes produced,” Zilnicki says.

“Weather, especially early season rainfall, influences the opportunity for yield gain with controlled-release nitrogen,” Menasha says. “When leaching rain events occur in April or May, there is a trend toward increasing yields with controlled-release nitrogen over conventional fertilizer applied at the same rate and, therefore, the potential to reduce nitrogen rates and cost.”

The research team has also tracked the economic value of controlled-release nitrogen use. In on-farm, side-by-side trials of controlled-release nitrogen and conventional nitrogen fertilizer over four years, potato and sweet corn growers reported saving $221 an acre, which reduced nitrogen applications by 14 percent, a net gain of between $101 and $505 an acre without compromising crop or quality.

Pinpointing opportunities

Evaluation on a farm-by-farm basis helps pinpoint opportunities for controlled-release nitrogen benefits. Menasha notes: “On-farm trials allow growers to try a practice or product under their specific growing conditions. We recommend trying controlled-release nitrogen at a grower’s standard nitrogen rate and reducing accordingly after seeing how it works under different conditions on your soils.”

The New York Farm Viability Institute provided Extension with a grant for the controlled-release nitrogen work on Long Island. For Zilnicki, the grant-funded research is cost-effective.

“I appreciate Extension reaching out when they have a grant to bring new things to the farm to test before we invest money in something that may or may not be helpful,” he says.

Menasha’s research has also experimented with controlled-release nitrogen/conventional nitrogen blend applications. She currently suggests blending a 44-0-0 controlled-release product with a 90-day release profile with approximately 25 percent soluble nitrogen fertilizer for potato production, so 75 percent of the total nitrogen in the blend is controlled-release nitrogen.