Nitrogen management and sources for winter wheat

August 02, 2019

Fertilizer application flexibility can allow producers to make better decisions about application timing, and may result in a more effective and efficient application. When soil moisture is adequate at the time of seeding, side band application of all nitrogen fertilizer can be considered, particularly in the Brown and Dark Brown soil zones where potential N losses are low. However, splitting a fertilizer application between the fall and spring gives the flexibility to see how the crop survives over the winter before adding more fertilizer. Flexibility in the spring allows you to better time the fertilizer application with forecasted moisture and subsequent yield potential, allowing for a more effective application, limiting N losses. Research conducted by Dr. Brian Beres and colleagues compared the effects of several fertilizers to yield and protein content of winter wheat: SuperU (Koch Agronomic Services), Agrotain (Koch Argronomic Services) and ESN (Agrium Advanced Technologies) Urea and UAN.

What was the best nitrogen management approach?

Split applications of nitrogen half applied as a side band at seeding and the other half applied as spring broadcast showed the best yield and protein response, particularly with Agrotain and SuperU. That being said, Urea was not too far behind the results of Agrotain and SuperU. Split application of half as a side band at seeding and half broadcast in the fall typically showed the least promising results with the exception of SuperU. This means that if this management strategy is your only option, SuperU will be your best nitrogen source for the job, if conditions for N loss are present. If conditions for N loss are minimal, then urea is the most economical product to use. Often, conditions for over winter N losses are relatively low in the Brown and Dark Brown soil zones in Alberta. Also, spring broadcast N is less efficiently taken up versus fall banded N provided over-winter N losses are low.

How flexible is SuperU application timing?

Overall, SuperU application is very flexible and can be split applied to reduce management risk over the winter. SuperU produced the highest yield and protein when half was side banded at seeding and the other half was broadcast in the late spring over all the sides of the study. SuperU was the only fertilizer that had similarly high yield to the most effective timing (split applied in fall and late spring) when 100% was side banded in the fall. There was relatively low risk for decreased yield when SuperU was applied either in the fall and/or the spring though there was a benefit to stand survivability when some N was applied in the fall.

Was the response to Agrotain similar to that of SuperU?

Overall, Agrotain had one of the strongest yield and protein response. Similar to SuperU, there was also a low risk for decreased yield when applied at different timing either in the fall or spring, allowing for more flexible application. Like SuperU, Agrotain also produced the highest yield and protein when half was side banded at seeding and the other half was broadcast in the late spring.

How does urea stand up to the EEFs?

Urea had a similar amount of flexibility to SuperU. When urea was half side banded at seeding and half broadcast in the late spring, it had almost the same protein content as what SuperU provided.

Is there value in utilizing ESN?

The greatest utility for ESN is when N is placed with seed, for example. single shoot. The Beres et al. study showed ESN is not the best fertilizer for in-crop applications. ESN caused the lowest yield when half was side banded at seeding and half was broadcast in the late spring compared to urea and SuperU. This is likely because the ESN granules are stranded in the thatch layer, which can be thick in no-till systems, and prevent water from penetrating the polymer coating to initiate hydrolysis. Sidebanding ESN can at times improve yield or protein, but Beres has shown in his studies that 100% ESN is not needed as 1:1 blend with urea produces the same results.

How did the efficiency of UAN compare to the other fertilizers?

Overall, UAN was the least efficient fertilizer and resulted in the lowest yields. This may be because of its volatility and leaching potential; therefore, use of N stabilizer is highly recommended. It was also the most sensitive to environmental conditions.

Having timing flexibility when applying fertilizer can make a difference because you can time applications more based upon moisture expectations, and get better efficiency out of your fertilizer with potentially less loss. SuperU, Agrotain and urea displayed optimal application flexibility.

I would also note that broadcasting of urea or UAN can lead to substantial nitrogen losses due to volatilization and run-off, depending on the season. Especially in hot, dry and windy conditions. If utilizing a broadcast system, consider an N stabilizer such as Agrotain Plus and apply these products prior to at least ¼” of rainfall to help with breakdown into the soil.

A note from Jeremy: