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Is there still time for Nitrogen??

Brian Arnall, Precision Nutrient Management Specialist.

With much of the states wheat crop receiving a drink, finally, the wheat has really perked up. While it the end of March while I am writing this, my story on applying nitrogen (N) is that it is not to late. While the early planted grazed wheat is beyond hollow stem the later planted grain only is a mixed bag of stages but moving very quickly to the point of hollow stem if it is not there already.

But if you look at the figure below that is the first dot around 650, when the wheat plant is still 100% leaf and no steam. At this point in the game we are looking at have used 25% of the total N. That means, we still have a lot of N to take up, and time to get it on.

Figure 1: Nitrogen uptake of winter wheat from planting to harvest. Adapted from Silva et al.2019. Kansas State University dissertation.

We have work on grain only wheat and graze out wheat that with out question shows that the crop can respond to nitrogen applied after hollow stem.

Figure 2: Image of the delayed nitrogen study with treatments identified. No N is the Zero nitrogen check, Pre-plant received 90 lbs N preplant, DAVD stands for Days After Visual Deficiency so 0DAVD 90 lbs was applied at the first sign of N stress while 56DAVD had 90 lbs applied 56 days after deficiency developed. Summary of this study is highlighted in the post “How long can wheat wait for Nitrogen? One more year of data.”
Figure 3. Gain-yield production (dry matter yield * net energy for gain)in tons per acre, for each N rate application; 60 lbs of N pre-plant, 120 lbs of N pre-plant and a split application (60-60) of 60 lbs of N pre-plant and 60 lbs of N top-dress. These are presented for each location Chickasha (Left) and Lake Carl Blackwell (Right). Each season gain-yield is denoted by the value within each bar and the system total is denoted by the value above each bar. See full article in “Split N application pays in graze out wheat.”

In fact when we look of the past five years of work performed by both the Soil Fertility project and the Precision Nutrient Management project we can wee that all nitrogen applied in-season near the point of hollow stem out yielded pre-plant N applications 32% of the time and had better protein content 74% of the time.

Summation of 40 nitrogen studies conducted by Dr Bill Raun and Dr. Brian Arnall from 2017 to 2021. See full write up in post “Value of in-season application for grain only wheat production”.

So if you are looking at a wheat field wondering about making that very expensive call, here are some thoughts. First, do I have moisture? Finishing out is not guaranteed everywhere, so if I am going to pay for expensive N I want to make sure I have a little moisture in the tank. Second, am I seeing signs of deficiency? If your fields are short N already (Yes they can recover read the blogs below) that means they will runout soon. But more importantly when N is short it is also much more efficient. If you apply 40 to 60 lbs of N on a yellow crop you could expect conversions of 2. to 1.5 lbs of fertilizer N per bushel. Finally just a thought that was supported by a conversation with Dr. Kim Anderson, if we get the moisture to finish out a good crop what I am hearing is that there will likely be alot of fields that end up short on N. What could be setting is a nice protein protein premium. While environment has the biggest control on protein we can manipulate it with N applied at jointing and in the right environment N applied at flowering.

Key Research Take Aways:

  • Nitrogen applied at or period after hollow stem can be taken up by the plant and contribute to grain yield.
  • Nitrogen applied during periods of peak up-take has greater efficiency.
  • Protein levels are typically higher when nitrogen is applied in-season.
  • Even if wheat is nitrogen stressed at hollow stem, yield can be fully recovered if N is applied accordingly.

Final Thoughts

  • Even given Extremely high N cost, IF wheat is showing signs of N stress the probability of positive return on investment of an N application is extremely high.
  • In short even if N is $1.20 a lb, when wheat is worth $8 or better there is value for this N. A late application made on a deficient crop is likely to be extremely efficient and I would consider 1.5 lbs of N per bushel.

Send any questions or comments my way.
Brian
B.arnall@okstate.edu

Previous Blogs Cited above.


2 Comments

  1. […] agree that there is little need for pre-plant, although I have said regardless the conditions, see Is there still time for nitrogen. Does this mean I wont need any N, sorry you probably will. Why? This is where the Nitrogen Cycle […]

  2. […] when talking about the past N timing results How Late Can You Wait there are comments about the risk of waiting and the crop needing N to get going. Most of the work […]

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