Ask the Agronomist – Top Questions & Answers for Cereals

golden wheat field ready for harvest

Nitrogen is an essential nutrient to stimulate tillering, head development and protein storage in grains. From spring-and-winter wheat to oats, we receive a lot of questions about this important macronutrient, specifically ESN, for cereal crops. Nutrien Senior Agronomist Dr. Alan Blaylock is answering some of these questions in our latest edition of Ask the Agronomist.

I am a producer in western South Dakota thinking of trying ESN in furrow with wheat. I am curious on safe rates and whether liquid starter fertilizer should be applied with it.

We have done extensive studies with ESN in-furrow, or seed-placed, on cereals and canola. Based on what research we have done, we recommend ESN can be applied in the seed row at up to 3X the safe rate of urea for your planter configurations and soil type. In many cases on dryland wheat, it may be possible to apply all of the needed N in the seed row. Wheat is planted with narrower row spacing than corn, so the per acre rate can be greater.

The table below shows safe rates for different row spacings, opener type (seed zone width), and soil texture. This table is based off a safe rate of 2-3X the safe rates of urea published by the Canadian provincial agencies. It provides the safe rate in lbs N/ac as ESN. The high end of the range represents 3X the safe urea rate; the low end of the given range is 2X the safe urea rate. One must also account for any other fertilizers that are being placed with the ESN – phosphates are generally safe, but urea, ammonium sulfate and others not so much.  For example, if using 100% ESN in-furrow, the safe rate is up to 3X urea; if 75% of the blend is ESN and 25% is urea, use up to 2X the safe urea rate. If 50% of the in-furrow blend is ESN, limit the rate to 1.5X the safe urea rate.

We would like to try ESN on oats. Any thoughts or recommendations?

Typically for a spring-planted cereal we would recommend using ESN to comprise about 50-75% of your expected nitrogen needs. The remainder could be urea or ammonium sulfate blended with the ESN. In most cases, you would apply the same total amount of nitrogen. If you have nitrogen loss conditions, the advantage of ESN would be realized in a yield increase over typical pre-plant applications of other conventional nitrogen fertilizers. For conditions of greater potential nitrogen loss, use the higher end of this blend range. For drier conditions, especially if fertilizer is not to be incorporated, use the lower end of the range.

For your oats, you could blend all your P, K and other nutrients with ESN for one dry broadcast application. If doing tillage, make this application before the last finishing tillage pass or before seeding.  The seeding will provide some minimal incorporation which would be preferred. If you need sulfur, use ammonium sulfate in the blend to comprise the non-ESN nitrogen up to your sulfur requirement. If sulfur is not needed, you can blend with urea to supply some immediately available nitrogen to get the crop started strongly.

What would the affect be of the polymer coating if ESN were top dressed on standing wheat? It would be laying on the surface subject to moisture and whatever irrigation that was received and the heat of the air and sun. Would it remain stable even after it was wet and dried?

ESN is used for spring top-dress of winter wheat in many areas of North America. As you point out, the environment on the soil surface can be more variable than the environment within the soil. The soil surface will usually be warmer than the temperature several inches deep and moisture is more variable. Top-dress of ESN on winter wheat has proven effective in spite of this variability provided the timing and blend with readily available N is appropriate.

ESN does remain stable on the soil surface and release will continue at an appropriate rate for the crop if intermittent moisture is present from rainfall or irrigation. Under irrigated conditions, water would not be limiting, and ESN release is quite consistent and predictable. Wetting and drying cycles have little effect on the release unless it stays dry for long periods.  Even heavy dew can provide sufficient moisture to promote release, but greater moisture would be needed to move this nitrogen into the soil. On dryland wheat in arid and semi-arid areas, incorporation of ESN at planting would be preferred. Top-dress ESN in these environments would sometimes be exposed to prolonged drought, in which case release may slow, and this nitrogen could stay at the dry soil surface and its availability reduced.

As for volatilization risk, we have not seen significant volatilization from surface-applied ESN. Because the nitrogen is released slowly, the chemical conditions that cause volatilization are minimized. An example of this from a study in Washington state is shown below.  Ammonia volatilization from ESN was similar to that from an unfertilized control.

ESN has worked well in southern Idaho as a fall application at planting but is also excellent for early spring top-dressing in irrigated wheat. The best timing for top-dressing ESN on winter wheat is late winter or early spring before or at the time wheat breaks dormancy. So for eastern Idaho, that is likely early to mid-March, or as soon as soil conditions allow one to get in the field. ESN should be blended with another soluble N source, such as urea or ammonium sulfate, to supply immediate needs of the crop.  This blend is adjusted according to time of application. Typical recommendations for top-dressing are as follows:

  • A blend supplying 75-100% of the spring N needs as ESN is recommended for late winter/early spring application prior to green-up.
  • A blend supplying 50-75% of the N as ESN is suitable for applications at green-up.
  • For applications after green-up thru the five-leaf stage, use a blend comprised of 30-50% ESN.
  • ESN is not recommended after the five-leaf stage.

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Disclaimer: This information is not intended to be complete or detailed use recommendations for all geographies, crops, or applications. User assumes all responsibility for proper use and handling for specific geographies, crops, and applications. Please consult ESN recommendations and/or your Nutrien ESN representative for complete recommendations for use. Consult ESN recommendations for more information.