The N+S Dilemma

“What are my options for late nitrogen applications?”

As wet conditions persist throughout various parts of the province, nitrogen and sulphur applications have been challenging to get done. In the southern most parts of the province, some fields have flag leaves emerging which can be a big problem if no nitrogen and sulphur have been applied due to wet field conditions. The Wheat Team has been getting lots of questions asking “What are my options?”

As many are likely aware, helicopters have been buzzing around some parts putting nitrogen on as a “rescue” pass. Speaking with industry agronomists, application rates with the helicopter range from 30 to 100 lbs of actual nitrogen. Since the helicopter charges by weight, the economics of 100 lbs of N start to favour a second pass with a ground machine (assuming field conditions will be fit to get the second pass done).

Those applying 30 pounds of actual nitrogen with the helicopter, what is the plan for the balance of the crops nutrient requirements? The answer comes down to the source of fertilizer to be used and the application timing. In 2018 we ran the second year of our fertility trials with an independent research company. The original intention of this project was to understand the impact of fertility approach on yield and protein in Hard Red Winter Wheat. We are certainly are finding it useful to draw on for agronomy to relate to all wheat classes.

There were eleven treatments in total, all small plots replicated four times, but we will refer to three here briefly.

Treatment 4 :
80N + 8S at Green-Up (as UAN/ATS streamers)
80N + 11S at GS 32 (as UAN/ATS streamers)
Yield 95.3, Protein 13.6

Treatment 7:
80N + 8S at Green-Up (as UAN/ATS streamers)
80N + 11S at Flag Leaf emerged (as UAN/ATS streamers)
Yield 81.6, Protein 14.0

Treatment 9:
80N + 8S at Green-Up (as UAN/ATS)
80N + 11S at Flag Leaf emerged (as AMIDAS granular)
Yield 93.5, Protein 14.0

The yield was really dragged down in Treatment 7 when the liquid fertilizer was applied to the crop with Flag Leaf emerged. The technician made specific comments and noted the significant visual burn in those reps. If UAN is something you still want to carry forward with and the flag leaves have emerged, use extreme caution!

Ways to make UAN+ATS application as safe as possible…
• Avoid application in the sunny parts of the day. The leaves are sensitive.
• Consider to dilute UAN with water, this will make more drops, but the droplets half as concentrated. Be sure to stay within proper operating pressure and rate for your streamer nozzles. Target is still to have large droplets that reach the ground.
• Try to apply at night, or when dew present, more dilution, UAN droplets should roll off leaves easier. Can even be effectively applied during a light rain.
• Including ATS can increase burn, but the crop will still need the sulfur, so keep it in the mix. Just be more careful.

The AMIDAS product is an example of a granular product that can be effectively spread in flag leaf wheat. It will almost eliminate the risk of burn injury, maintain yield and enhance protein. If AMIDAS is something you are interested in trying, make sure the application equipment is equipped with row crop tires to minimize crop damage. Also, the same tracks can be used to apply the T3 fungicide if equipment application widths line up.

NOTE: This is a single year from a single data set, grain of salt required. However, we do think that it can explain the risk potential of a flag leaf application of liquid fertilizer. Check the plant staging, if the flag leaf is just poking past collar, but not fully flopped out, the application should be safe. Proceed with Caution if the flag leaf is fully out.

For more information on nitrogen and sulphur timings read last year’s story “GO” on BIG, or GO on HOME? Click the link below.

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