LETHBRIDGE – The decision to stop manufacturing ammonium nitrate in 2006 partially because of its link to bomb making prompted fertilizer companies to develop new products to replace it. One product, a slow release, polymer coated urea produced by Agrium, is called ESN.
Researchers have been working with ESN for a few years, trying to establish its best fit for western Canadian conditions.
At the recent Agronomy Update conference in Lethbridge, Agriculture Canada researcher Brian Beres said initial ESN prototypes – Types 1 and 2 – were 20 or 40 day products. He said commercial ESN that is now on the market is more like a 30 day product.
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One study in 2003 compared seed applied uncoated urea, Type 1 ESN and Type 2 ESN with winter wheat.
“All three products, through the 30 kilograms per hectare rate, had stable plant populations. Once we exceeded that with the uncoated urea, we saw detrimental effects on plant populations,” Beres said.
“Beyond 30, uncoated was not sustainable, but both ESN products, through to the 90 kg rate, were conducive to stable and healthy plant populations. Beyond that, we start to see declining populations with the Type 1.”
Another study compared seed-placed and side-banded treatments using ESN.
“We had quite a nice benefit using ESN in a seed-placed situation, along with good yield benefits with side banded.”
A separate study in southern and central Alberta involved the effects on protein management using uncoated urea, polymer coated ESN and a blend of both. Researchers used two rates – one based on soil test recommendations and another 50 percent more than that – to see if they could influence protein levels.
“The ESN, averaged across all factors, we generally had as good (yield) results or a slight benefit compared to the uncoated or blend.”
Beres said this study, which was conducted on dryland and irrigation sites, found no increased yield with the higher nitrogen application rates. All treatments succeeded in boosting winter wheat protein levels over the levels required for a protein premium.
However, he said protein levels were significantly lower in the ESN fertilizer form in the dryland tests. He felt the release was either too slow or inhibited by dry weather late in the season because the ESN treatments on irrigation were as good or better than uncoated or the blend.
“Boosting fertilizer rates to 150 percent of soil test recommendations did not provide an economic return for protein content,” he said.
“Dryland protein only changed from 13.9 to 14 percent, while irrigated protein moved from 12.6 to 12.7 percent.”
A split fertilizer application successfully increased yield and protein levels, but required that the in-crop broadcast application be followed by moisture. Timing just before a rain for dryland applications would be critical for success.
Beres said southern Alberta researchers conducted trials with ESN nitrogen on irrigated timothy hay in 2004 and 2005. Spring broadcast coated urea consistently yielded lower than urea or ammonium nitrate treatments for first cut harvests.
Protein content was lowest on the first cut for coated urea at the Leth-bridge site, but was highest for the second cut for coated urea at the Bow Island site.
Another trial comparing various application treatments produced lower first and second cut yields using the coated urea.
Beres said the data suggests the release of the coated urea may be too slow for timothy production.
He said a contributing factor may have been that urea granules became caught in the timothy thatch. Coated granules could be found in the thatch weeks and months after application.
Beres feels ESN is best suited for seed-placed applications. He said spring broadcast applications of ESN are not as effective as broadcast ammonium nitrate or urea.
The added fertilizer inputs of higher nitrogen rates and polymer coated forms of urea did not influence yield or protein in winter wheat to a level that would recover the added input costs, which at the time of the study were 32 cents per pound for urea and 44 cents per lb. for ESN.
