• We’re coming to the end of flowering in canola and nearing an opportunity to add yield with foliar nitrogen. Producers in the UK apply liquid urea at the early pod stage to generate higher oil content and yield. The results have been mixed but in some cases they’ve found a 7 to 9 bu/ac yield increase from a 25 lb/N/ac application using liquid urea solution. I think a quick tissue test for nitrogen at the end of flowering could show you whether nitrogen is limiting in the plant. If there is adequate moisture in the soil profile, a liquid top dress of urea might be a new avenue to explore in our canola production systems.

    The majority of producers are using liquid urea instead of liquid UAN (28-0-0) for its lower cost, increased uptake efficiency and reduction in leaf burn. That’s not to say that liquid urea doesn’t burn because it will under high light intensity or temperatures above 18 degrees C. The key to reducing scorch is water volume.

    Here's a list of tips used by my UK friend Nick Ward to give you some ideas.

    • You can use any 46% urea and tip it into the water tank and circulate it using a pump. 'Distressed' urea is usually used (ie. sweepings out of a shed) as it is cheaper and doesn't need to have spreading quality.
    • We spray on 150-200 litres of 20% nitrogen solution per hectare at the end of flowering. (That works out to 25 lbs/N per 15-20 US gallons/ac.)
    • If temperatures are hot, apply in the evening. We don't dilute it, but if you were concerned about heat, dilute it with the same amount of water. I've applied the urea solution up to 23 degrees C and didn't have any problems with leaf burn.
    • 20% is the max strength that you will get. I think granular urea may be the better option as prilled has an oily coating that leaves a film on the liquid.
    • For our main liquid fertilizer solutions we would use an ammonium nitrate/urea mix in solution to get the concentration up to 37%. But for this job a urea solution is a lot gentler and will cause way less scorch even in warmer conditions.

    And I've added a couple of points of my own:

    • Add 3.6 lbs of urea per gallon of water to give you 25 lbs/N per acre and apply solution at 15 gal/ac.
    • You can delay maturity with a late season nitrogen application so those who've finished flowering by late July, early August might be able to afford a slight delay in maturity.

    Steve's quick math
    Let's see what this nitrogen boost could pay back.

    25 lbs/ac × $0.69 lb/N: $17.25 ac + $3.50 application = $20.75/ac
    50 bu/ac canola yield × 8% × $10.00 bu = $40.00/ac
    ROI: 2 to1

    In theory, if we were to see the same response as some have in the UK, the additional $20.75 ac investment in top dress nitrogen may net you a 100% return on your investment. I believe there is value in spreading out your nitrogen applications in canola and this might be a way to generate better nitrogen use efficiency rather than applying all of our nitrogen up front which by now is almost 90 days ago. Even a 5% yield increase at today's prices makes this option viable. SL

Your Comments

Chris Decker - 2015-03-16
I agree a very good idea. not to apply all N up front.

Randy Saskiw - 2015-07-19
Tried it for three years in field trials and one trial out of 25 had a positive economic response. Conclusion: W. Canada growing season isn't long enough to see the benefit consistently.

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