“Many people blame ethanol for the increasing cost of fertilizer,” said Richard Ferguson, UNL soils specialist. “It is a factor, because corn requires more nitrogen than some other crops and the increased acreage in corn has increased demand.”
Ferguson also listed a number of other contributing factors, including greater transportation cost brought on by rising petroleum prices, a large decline in domestic production, particularly anhydrous ammonia, and the declining value of the dollar compared to the euro and the pound.
Although the price of nitrogen is about twice its cost last year or two years ago, he said, the price of corn has increased more. So UNL’s fertilizer recommendation, which has an economic component, will be higher this year. Ferguson advised producers to keep in mind that the value of non-purchased nitrogen has also doubled, so it’s important to consider those sources and to account for them.
Among non-purchased sources, Ferguson listed residual nitrogen mineralized in the soil, organic matter, manure and nitrogen fixed by legumes like soybeans and alfalfa. Irrigation water in some parts of the state also carries significant nitrogen, he said.
Ferguson encouraged producers to sample soils before applying manure or purchased nitrogen. Some contributions from legumes often don’t show up in a soil sample, though; those contributions can be calculated on the basis of the crop and the stand.
If removing alfalfa, for example, producers should give a year’s amount of credit for a good stand and less for a spotty stand, Ferguson said. UNL provides tables for determining how much credit to give. The tables directly account for timing of application for corn; side-dressing is the best time.
“We increase the amount of nitrogen by five percent if applied before planting and by another five percent if applied the previous fall,” he said. “The longer nitrogen is in the soil, the greater the likelihood it will leach away.”
When planning to apply manure nitrogen, producers should analyze nutrient content of the manure before determining how much to apply.
Although new nitrogen fertilizer formulations keep coming to market with controlled release and enhanced efficiency, UNL recommends that people use the least expensive source of fertilizer they can apply. Research done at UNL and other land grant institutions shows that, as long as traditional sources of nitrogen are applied properly, there is no difference in yield.
For more information, decision-making software and tables for determining nitrogen credits, go to: http://soilfertility.unl.edu/ or contact your nearest extension office.
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