OSU's Brian Arnall Answers the Question, 'Is It Too Late For Nitrogen Application?'Tue, 27 Mar 2012 10:20:18 CDT
Precision Nutrient Management Extension Specialist Brian Arnall has said many times in the past that the nitrogen cycle and Oklahomaís environment keeps him busy and employed. This year is no exception, he says. He says the calls from producers across the state are rolling in asking if it is too late to fertilize or not.
Arnall consulted OSU Soil Fertility Researcher Dr. Bill Raun and discussed the likelihood of success and fertilizer options. Here are the results of their conversation:
∑ The likelihood of increasing yield is better if N is applied prior to flag leaf.
∑ Some fields have been deficient so long maximum yield is no longer possible
∑ N applications appled at or soon after flag leaf have a 33% chance of increasing grain yield.
∑ Foliar application of UAN will result in leaf burn if temperatures are greater than 65 degrees.
∑ Avoid high rates of N with a fungicide; surfactants used with fungicides increase leaf burn.
∑ Pre-flag leaf rates of 20 to 30 lbs. of N per acre, 40 lbs. max.
∑ Keep in mind it takes 1.5 to 2 lbs. N to make a bushel of wheat.
∑ Of N sources, UAN with streamer nozzles or urea before a rain event are the best options.
∑ Wheel track damage will occur; avoid floater rigs.
∑ Consider area lost from traffic versus potential gain.
∑ We do have the soil moisture to make it to yield across much of the state.
For many of the questions that we are receiving, there is no concrete research to use as a guide. This being said, OSU has many projects that are in the field this year which will get at topics. To list a few:
∑ Impact of N applied at flag leaf and post flowering on yield and milling/baking quality.
∑ Timing and source of late N on yield and protein.
∑ Can UAN be diluted and used as a late N foliar fertilizer without burn/yield loss?
∑ Impact of droplet size on foliar N utilization.
∑ Impact of late season foliar N and S on grain yield.
Arnall said producers are welcome to contact him with questions at 405-744-7122 or via email at: npk.okstate.edu
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