Ask The Agronomist – Top Questions & Answers For Canola

Canola is a sensitive crop that requires extra care when applying fertilizer, particularly nitrogen, to achieve high yields and maintain crop health. From application and nitrogen release to crop maturity and salt index, dive into the top four questions we have received from growers about canola, answered by ESN agronomists.

Question: ESN was applied in a drill blend sideband two inches into field capacity moist soil. How long of a delayed release can we expect in soil that is six percent organic matter, pH of 5.5 and CEC of 16-20? Soil is moist and it continues to rain.

Answer: The release of nitrogen from ESN is regulated by soil temperature. Within a few days after application in moist soil you will notice granules begin to take in water. The solid urea inside will dissolve to form a capsule of urea solution. As the urea liquifies, some nitrogen can start to release. The “lag time” or delay would be from a few days to a week. There will always be a few granules that will release immediately due to imperfections in the coating and some handling effects. You should normally expect to have about 15-20 percent of the nitrogen released in about a week to ten days and maybe about 20-40 percent released in about three weeks depending on soil temperatures.

The amount of rain does not affect the release rate until soil becomes very dry—near the permanent wilting point—at which time release could be slowed by insufficient moisture.


Q: If potassium was to go to a complete liquid fertilizer starter blend could I still put ESN in the seed row? Would the liquid dissolve the polymer coating too quickly?

A: We do not have any direct observations of combining ESN in furrow with a liquid starter, but there should be no reason ESN release would be affected by being in contact with a fertilizer solution. There are some herbicide solvents and some other chemicals that can degrade the coating, but water-based materials (your fertilizer solution) have no effect. You will still need to observe safe rates for the combination of starter and ESN—the two are additive. As long as you are within safe limits, we would not expect any issues.


Q: Is there any current information on how ESN does or does not change crop maturity in canola?

A: We have not seen any reports of ESN delaying maturity in canola or in other crops in the U.S. There was a study in northern Alberta by Mackenzie Ag Research in which ESN actually hastened maturity in canola by a couple days.

There are a variety of factors that could cause maturity delays. Excess nitrogen beyond crop requirements or not balanced by appropriate phosphorus and potassium levels can delay maturity. Deficiencies of some micronutrients, particularly zinc, can also delay crop maturity.


Q: What is the salt index of ESN?

A: The salt index of ESN is a bit of a tricky question. To be technically correct, we would need to say the salt index is the same as urea, because ESN releases from the coating as urea. The difference is that the controlled release maintains a much lower concentration than an uncoated granule that dissolves immediately, so the effect of that salt index is greatly reduced from uncoated urea. It’s as if you’re applying a much lower per-acre rate. This is the main reason ESN is safer for seed-placed applications.


Smart nitrogen management for canola

To learn more about ESN’s performance in canola, view trial data, application recommendations or submit your own question to Ask the Agronomist.

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