Agronomy Library > Soil Conservation

Environmentally Smart Nitrogen and the Direct Seeding Advantage - Direct Seeding Advantage 2006
Author: Ross McKenzie, Alberta Agriculture & Food & Stu Brandt, Agriculture & Agri-Food Canada
Date Created: November 22, 2006
Last Reviewed: March 01, 2007

New slow-release, polymer-coated urea fertilizer, ESN™ (Environmentally Smart Nitrogen) was registered for use in Canada, in July 2006, for both food and non-food crops. This new polymer slow-release technology is leading edge and world class. Agrium is now the world leader with this technology. Over the past 10 years, Agrium Ltd. has undertaken development of this unique polymer to coat urea to control the release of N to improve fertilizer use efficiency and minimize N losses to the environment. Presently, all ESN used in North America is manufactured in Alberta, at the Agrium Carseland plant. 

The efficiency of applied N fertilizer is a function of a number of factors. Environmental conditions, N fertilizer form, and time and placement of N fertilizer all strongly influence potential losses of applied N fertilizer. The most common commercial N fertilizer applied to soil is urea [CO(NH2)2]. Urea converts to ammonia (NH3) and can potentially be lost to the atmosphere (volatilization) at this stage before conversion to ammonium nitrogen (NH4 +). When soil conditions are warm, moist and well aerated, ammonium is rapidly oxidized to nitrate nitrogen (NO3 -) through nitrification, a biological process performed by highly specialized soil bacteria. Loss of nitrate is caused when soils are warm and wet causing an anaerobic process (denitrification), where soil microbes strip oxygen from nitrate to convert it to gaseous nitrogen forms. Wet soil conditions will also result in downward movement of nitrate below the plant root zone and into ground water (leaching). 

The porous polymer coating permits water to slowly permeate through the coating into the fertilizer granule to slowly dissolve the urea, then allow the dissolved urea to gradually diffuse through the polymer coating into the surrounding soil. Soil moisture and temperature are the two environmental forces that have the greatest effect on the rate of urea release. By coating urea fertilizer granules with this polymer, the urea is protected from environment losses. ESN polymer coated urea products offer huge opportunities to significantly reduce potential N fertilizer losses (volatilization, denitrification and leaching), which would result in increased nitrogen fertilizer use efficiency, result in higher crop yields and improved crop quality. 

A major benefit of ESN is reduced N losses resulting in higher N use efficiency by crops. This would lead to reduced N fertilizer requirements if N fertilizer uptake was more efficient; higher yield potential of 5 to 15 % and for crops such as spring wheat could result in higher protein levels, and premium payment for higher protein. 

By slowing down the release of N using polymer-coated urea, significantly higher N rates can be safely seed-placed. Recent work with two proto types of polymer coated urea seed-placed with winter wheat, showed that up to 120 kg N/ha of coated urea could be safely seed-placed versus only 30 kg N/ha of urea (McKenzie et al. 200x). Much higher rates of coated urea versus urea could likely be seeded-placed with spring wheat, barley and canola but this must be determined in a range of field trials in various soil types, under various environmental conditions. If substantially higher ESN rates can be seed-placed with reduced N losses, this would have a huge benefit to prairie farmers. Additional field operations specifically to apply N fertilizer could be eliminated and all N fertilizer could be safely seed placed. For direct seeding systems, single shoot openers could be used instead of more costly double shoot openers, which are presently needed to side band higher rates of N fertilizer. Using single shoot openers versus double shoot openers would result in less soil disturbance, less soil moisture loss reduced horsepower
requirements and lower fuel consumption.

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