January 21, 2004 | By: Laura Skillman
PRINCETON, Ky.

With the higher cost of nitrogen and the likelihood of it remaining at high levels, farmers may want to consider fine tuning their use of this fertilizer.

Nitrogen prices have increased along with the prices of natural gas, a key component in nitrogen production.  Knowing the optimum needs for a specific field, side dressing and injecting nitrogen are some areas where farmers can look to fine tune nitrogen use to get optimal yields at the most economical cost of production, said Lloyd Murdock, a University of Kentucky College of Agriculture agronomist.

“We have higher commodity prices today, which is good, but if you do calculations using 20 cents per pound for nitrogen and corn at $2.25 per bushel and look at the nitrogen trials done across the state, you are better off at the optimum use level of nitrogen for a field,” he said. “But most people don’t know where optimum is for their fields and usually are at the optimum level or higher.”

“As you increase the cost of nitrogen – 30-cents and corn at $2.25 – you are better off being at the optimum level or lower, not higher,” he said. “If $2.50 corn goes down to $2.25 or $2, then we really have to keep that in mind. It’s a philosophical change.”

To find the optimum, many producers use a pounds-per-bushel rate, a method Murdock says is not a good source. If you are using this method do not use more than one pound per bushel, he said.

Another source is the nitrogen trial information available through the UK fertilizer and lime guide, AGR 1. However, there are ranges in these guidelines and they still will not provide the best results for a particular field.

“To go beyond that is to take a basal stalk nitrate nitrogen test,” Murdock said. “You go into the field and take about 10 to 15 corn plants within three weeks after black layer stage and cut the plant off at six inches above the ground. Then, take the bottom eight inches of that and send it in for analysis.

“UK has a guide on how much nitrogen should be in that basal stalk and you can determine if you have enough or are in excess,” he said. “The work we have done looking at these nitrogen rates and the information from the test has been pretty good in helping us fine tune our nitrogen use.”

Murdock said he would recommend farmers with questions about their optimum nitrogen needs start with this test.

“Then as the price of nitrogen prices go up and corn prices go down, if you are not side dressing or if you are no-tilling and not injecting, you should consider that,” he said.

Using these methods can reduce the overall amount of nitrogen needed.

In moderately to poorly drained soils, side dressing can reduce the amount of nitrogen needed by 25 to 30 pounds per acre, he said. In poorly drained soils, if all the nitrogen is put out in early spring when soil can become saturated, denitrification can occur.

In no-till planting situations, applying nitrogen on the ground surface may result in nitrogen being used by bacteria to decompose plant residue rather can for new plant growth, he said. Bacteria can tie up 10 to 15 percent of the nitrogen applied, so putting the nitrogen below the plant residue eliminates that loss.

If farmers are using urea, a granular nitrogen product, in no-till production after May 1, they should also use a product that inhibits volatilization.

For more information on fine-tuning nitrogen use contact a local Kentucky Cooperative Extension Service office.

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Contact: 

Writer: Laura Skillman 270-365-7541 ext. 278
Source: Lloyd Murdock, 270-365-7541 ext. 207