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Foliar Nitrogen for Wheat Protein Enhancement — Do You Feel Lucky?

Researchers in Minnesota, N. Dakota and Saskatchewan have recently evaluated the use of foliar applied N (usually as 28% UAN) to increase or enhance protein of hard red spring wheat. Late applications may increase protein content but generally are too late to increase yield. Preplant or seeding time N must be applied at rates to optimize yield when late N is to be applied for protein.

Results and opinions of this practice are not consistent. Following are some of these differences.

1. Movement of foliar N into the plant European and US work with urea indicates that 60% of total N is recovered in the plant, and at least 80% of urea-N recovered in plants is translocated to grain. U of Manitoba work used 15N — labelled fertilizer and found less than 1% was taken up through leaves. Most uptake occurred after N washed to the soil and was taken up by roots. Others believe foliar N may increase plant nutrition and stimulate roots to extract more N (up to 1/3 of total plant N uptake may occur after heading).
2. Time of foliar N application US studies (7-10 days after flowering (anthesis)) Saskatchewan studies found superior protein enhancement at boot versus post-heading.
3. Application methods To maximize foliar uptake a fine spray for complete leaf coverage. To optimize root uptake, and minimize leaf burn, apply 28% in strips or bands to minimize leaf contact.
4. Leaf burning NDSU report yields loss is consistent only after 40% of leaf is damaged. Burn tends to occur along leaf margins and does not coalesce like leaf disease, allowing continued leaf functions. Leaf burn can be minimized through management. Leaf burn can be severe. Protein enhancement occurs as a result of yield suppression from leaf burning. Disease control studies indicate 50% of final yield depends on health and function of flag leaf.
5. Varietal responses Minnesota and NDSU find similar protein increase for high yield — low protein varieties and low yield — high protein varieties. Alberta studies found reduced baking quality (loaf volume) when protein was increased from 12% to over 16% using foliar urea in combination with heavy soil applications of 34-0-0

Level of Protein Enhancement

Following are protein enhancement levels achieved in various studies and the break-even protein premiums required to cover N cost (35¢/lb) and application and risk (application at $5/acre, and risk to provide a 2:1 return on N cost and applications). In all cases sufficient N was applied at seeding to optimize yield.

Study Foliar N rate (lb/ac) Yield bu/ac Protein enhancement Break-even premium (¢/pt/bu) to cover
Cost of N Cost of N, application, risk
NDSU — Carrington 30 lbs 30 lbs 15 lbs 15 lbs 28 dry 50 irrigated 28 dry 50 irrigated +1.1 +1.8 +0.2 +0.5 34 12 94 21 101 23 366 82
U of Minnesota — Crookston 30 lbs 60 lbs 90 lbs 54 54 54 +0.4 +1.0 +2.0 49 39 29 144 96 68
AAFC — Indian Head 15 lbs 15 lbs 42 Boot 38 Heading +0.9 +0.6 14 23 54 90
U of M Winnipeg 30-16 lbs 45 +1.0 23-47 46-94

*additional N required at seeding to raise protein one percentage point.

It is apparent that protein enhancement is not consistent. Profitability with this practice improves when:

  • Yields are high
  • Protein enhancement is great
  • N costs are low
  • Protein premiums are high
Historic Protein premiums for # 1 CWRS in ¢/bu (additional premiums for each protein level)
% Protein 95-96 98-99 01-02 03-04 04-05 05-06* 06-07*
15.5     0.10 0.10 0.26 0.27 0.22
15 0.16 .15 0.08 0.09 0.23 0.27 0.22
14.5 0.14 0.16 0.09 0.08 0.23 0.26 0.19
14 0.14 0.15 0.07 0.07 0.22 0.25 0.19
13.5 0.11 0.12 0.08 0.04 0.13 0.12 0.11
13 0.12 0.12 0.07 0.03 0.12 0.09 0.08
12.5 0.1 0.18 0.07 0.04 0.08 0.09 0.08
12 0.15 0.22 0.05 0.03 0.08 0.09 0.08
11.5     0.05 0.04 0.09 0.09 0.08
11     0.04 0.03 0.07 0.08 0.08
*based on payments made as of July 31, 2006

If growers are interested in this practice:

  1. Encourage them to try strips in fields — if farmers do gain experience with this, it may be very profitable to implement in years when projected protein premiums are high.
  2. Warn them of the possible consequences — leaf burn, possible yield loss, cost of N and application, etc. The level of protein enhancement may not be sufficient to move up to the next premium level.
  3. Offer suggestions on ways to minimize leaf burning. (Dilute 28% N half and half with water and apply later in the day since damage is greater with high temperatures, low humidity and high sunlight intensity.

For more information, contact your local MAFRD GO Representative.  

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