It's Time to Be More Accurate With Fertilizer

Using UNL rate formula even more important this year.

It's no secret that fertilizer supplies are tight, and nitrogen and phosphorus prices have increased dramatically in the last year.

Because of those factors, Charles Shapiro, UNL soils specialist in Concord, says that proper nitrogen fertilizer application at UNL recommended rates is even more important in 2008.

Nitrogen and corn prices have typically been in the 8-to-1 to 10-to-1 corn-to-nitrogen ratio, and UNL nitrogen recommendations were designed to be most economical in that range. Adjustments are needed when the ratio is either higher or lower, Shapiro says.

Recently, UNL introduced an adjustment to take into account the changing economic conditions.

With March corn at $5.07 per bushel and nitrogen prices at about 50 cents per pound, the corn-to-nitrogen price ratio is at the recommended 10-to-1 range. This will not significantly impact UNL nitrogen recommendations for Nebraska's corn growers this year, Shapiro says.

"The cost of under applying nitrogen is always a lot higher than over applying, but our recommendations are profitable. Since fertilizer prices are a lot higher now, it is more important that our recommendations be followed closely," Shapiro says.

The key to maintaining profitability is to know soil test levels and apply fertilizer accordingly, says Gary Hergert, UNL soils specialist in Scottsbluff. "Make sure you credit all nitrogen sources for the crop, then do the best job of applying nitrogen on a timely basis to maximize fertilizer recovery," he said.

Growers also can save money by working manure into their fertilizer programs. "Manure is an excellent nutrient source for nitrogen, phosphorus and micronutrients (zinc and iron)," Hergert says. However, manure also should be tested for nutrient content.

The old ballpark figure of 10 pounds nitrogen and 5 pounds phosphate per ton can be inaccurate for today's manure produced with corn byproducts. Nitrogen availability in manure and composted manure varies because nitrogen must be converted from organic to usable inorganic forms. The crop should be monitored mid-summer to see if additional inorganic nitrogen may be required to reach yield expectations.

Phosphate fertilizer also has almost tripled in price.

"I've been telling producers to follow the management guidelines we've stressed for years. Row application is more efficient than broadcasting, but over time it will not build your soil phosphorus level," Hergert says.

More information about nitrogen and phosphorus rates and costs, including the UNL Corn Nitrogen Recommendation Calculator, is available at UNL's soil fertility Web site at

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