November 14, 2007 | By: Laura Skillman

Soaring fertilizer prices may have farmers considering using less on their crops. However, the best option is for farmers to determine what amount they really need and apply the fertilizer when it will provide the optimum benefit, says a University of Kentucky College of Agriculture soils specialist.

“Prices are very, very high for phosphorus, potassium and nitrogen,” said Lloyd Murdock, UK extension soils specialist. “Demand is up from all over the world. We’ve been used to cheap fertilizer for decades and haven’t had to worry much about efficiency. Now we have to think about efficient use of fertilizer more than we ever had.”

Murdock said he expects farmers to make more judicious use of their fertilize dollars and his big concern is that they may quit using it. Instead what they need to do is take soil samples every year or two rather than every three years.

This gives the farmer a good record of his fields and allows them to make fertilizer decisions using this history, he said. They must not be afraid to use these records to help them use fertilizer efficiently. Many have used the theory, “more is better,” and are afraid if they reduce their usage to the amounts recommended by their soil tests they may not be able to sustain their 200-bushel per acre corn crop.

“That’s something they have to overcome,” Murdock said. “I tell them I use these recommendations, and I get 200 bushels of corn too on a good year. We have had a lot of good crops in a row so we are removing higher amounts of phosphorus and potassium, but most of these fields really only need maintenance levels of these fertilizers. Many people like to put on maintenance plus and that’s one thing we’ve got to get them to understand that it is not necessary.”

Nitrogen, used heavily in corn production, has increased in price over the past several years because of foreign imports, prices of natural gas and other factors. Nitrogen fertilizer is used more than any other fertilizer, Murdock said. It is especially important for producers to understand their crops fertility needs and meet them.

Using UK recommendations available in publication AGR 1, he said he gets as good a crop as farmers do when they use higher than recommended rates of nitrogen. Murdock said he feels very comfortable with these recommendations that have been tested and tweaked through the years. The recommendations have a range from high to low which varies based on factors such as soil drainage and tillage methods.

“If the fertilizer cost is high and the commodity price is low, then you’d probably want to stay toward the lower level of the range,” he said. “But right now commodity prices and nitrogen prices are both high, so you’d want to stay toward the medium to high part of the range. These recommendations are very good and are an efficient use of fertilizers. There are also recommendations for side dressing corn that can also reduce nitrogen usage.”

In addition, there are a few products on the market that help reduce nitrogen loss from volatilization when using urea as the nitrogen source including Agrotain, an urease inhibitor, and ESN, a polymer-coated slow release urea. It is important to understand how these products work in order to get the best results, Murdock said. Information on inhibitors and slow release urea is available through UK’s publication AGR 185 at local extension offices. 

“I think we are in a transition period from a more liberal use of fertilizer to farmers taking a more conservative, efficient use,” he said. “This year I think we will see some people overspend while others will take a more conservative approach.”


Lloyd Murdock, 270-365-7541, ext. 207