Busting the myths around ESN: Polymer coating edition

ESN is a controlled release nitrogen fertilizer consisting of high-quality urea within a unique polymer coating. The coating forms a protective barrier that acts as a semi-permeable membrane surrounding the fertilizer granule. In this edition of “Busting the myths” we’re debunking some of the most discussed misconceptions about the polymer coating of ESN. How does the nitrogen release? What happens to the coating? Continue reading for the answers to these questions and more.

The following 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.


Myth: Fall application of urea in any form is problematic, regardless of placement method

Facts: Where fall nitrogen application is an acceptable practice according to soil type, environmental conditions, and cropping system, ESN is a great alternative to other N sources.  In dryland cropping systems in arid and semi-arid areas, such as Western Canada and the Great Plains, fall may be the preferred application time for ESN. Areas that remain warm and wet through winter and early spring may not be suitable for fall ESN application.  In these areas, ESN or ESN blends may be appropriate for some fall-seeded or winter crops. Consult your Nutrien representative to discuss fall ESN applications.


Myth: The release of nitrogen from ESN is moisture dependent

Facts: Soil moisture is necessary for the release process (diffusion), but soil temperature controls the rate of the process as long as sufficient water is present.  Moisture only becomes limiting when the soil surrounding the ESN granule is very dry – near the permanent wilting point.  Above that minimum moisture content, soil water does not affect the rate of release. The nitrogen release rate from ESN is temperature dependent, but there is not a specific “on-off” temperature. ESN can start releasing nitrogen at temperatures above freezing, but the release is very slow at lower temperatures and increases gradually as temperature increases.

The following diagram illustrates typical release curves of ESN and how ESN responds to soil temperature.

Myth: ESN does not blend well with other fertilizers

Facts: ESN blends well with other fertilizers and is designed to withstand normal handling processes. Proper handling and blending will not destroy the coating, but excessive blending may cause damage to the coating and reduce ESN’s effectiveness. To help avoid abrasion of the coating, add ESN to the blend last and mix for the minimum time required to achieve uniformity.


Myth: ESN’s coating breaks down and dissolves during the process of nitrogen release

Facts: ESN’s primary release mechanism is by diffusion through tiny, molecular-size pores in the polymer coating, leaving the coating intact during the process of nitrogen release. It does not dissolve in contact with water or break down and come off over the course of the growing season.


Myth: ESN granules burst if they freeze

Facts: ESN granules do not rupture, burst or disintegrate upon freezing and will remain intact for long periods in frozen conditions. Freezing temperatures stop the release of nitrogen from ESN because the diffusion of water into the granule is stopped. If ESN has not yet hydrated, the urea inside the coating will remain in a solid state until temperatures warm for diffusion to begin again.


Do you have questions about ESN not covered in this article? Browse the Smart Talk blog, ask an agronomist or send us a message on Twitter.