Nitrogen use efficiency

AFTER MANY YEARS of ongoing research on nitrogen delivery across a large number of Ontario crops, Dr. Tarlok Singh Sahota at Lakehead University Agricultural Research Station has results to report to farmers in all crop-growing areas of the province.

In short, while results varied to some extent with the weather and crops, Sahota has found that blends of urea with Environmentally Smart Nitrogen (ESN) improved crop yields, protein content, and nitrogen use efficiency in most crops, at a cost only nominally higher than urea.

Sahota published his study ‘Potential for Improving Modern Crop Production and N-Use Efficiency’ in late 2020 in the Journal of Agricultural Science and Technology. Technicians Blaine Tomeck, Harjit Dhillon, Limin Luan, and Muhammad Usman assisted with the research.

Sahota’s study on ESN started in 2006, initially on timothy, spring wheat, and winter wheat and later on with bromegrass, grass mixtures (timothy, bromegrass, orchardgrass), other forages (barley, silage corn, oat, MasterGraze corn, and sorghum Sudangrass), and canola.

ESN, a patented technology of Nutrien Inc., is a polymer-coated urea that contains 44 per cent N and allows for water entry through micropores, resulting in slow N release. Nutrien claims that eight to 15 per cent of N is released in the first 10 days, between 40 to 60 per cent in the first month, and about 85 to 90 per cent within two months. In comparison, Sahota explains that urea quickly hydrolyses in soil in three to 10 days; all the N is converted into nitrate that is susceptible to leaching and denitrification under excessive soil water conditions. In addition, N losses from urea can also occur via surface runoff.

RESEARCH NEEDED

Sahota thought it was important to do ESN studies because previous research had found that globally, N-use efficiency in cereals was only 33 per cent, and that the ESN had the potential to significantly improve N-use efficiency while maintaining crop productivity. And, because the rate of N release from ESN is temperature-dependent, Canadian research was especially needed. There was no research on ESN and field crops in Ontario conducted before he started in 2006.

Sahota explains that a single N fertilizer, urea for example, can at times be too quick — or one like ESN too slow — in some environments to release N at a rate that properly addresses crop requirements.

“Crop plants need to continue absorbing nutrients throughout their growth, especially before the reproductive stage,” he says. “Total nutrient availability in soluble form at the early crop stage, again with urea as an example, when nutrient uptake is slow/and limited could often lead to losses of N: volatilization, leaching and denitrification depending upon soil and weather conditions. Urea is usually dissolved within hours and is converted into ammonium in two to four days and to nitrate form within three to 10 days. I therefore thought that systematic field experiments comparing the effect on yields of blends of quickly-available N fertilizers like urea with a slow-release format like ESN to just the commonly-used urea fertilizer should be conducted.”

SPECIFIC RESULTS

Sahota has found that the increases in yields using ESN or urea/ESN blends (2:1) compared to urea alone were economically rewarding across most crops. In terms of cost, he notes that though the price of ESN and urea can vary, ESN generally costs about 20 per cent more than urea, “and even if it cost 40 per cent more than urea, the yield increases would outweigh that cost.”

However, he found that in winter wheat, which has a longer growing season than spring-seeded annual crops, ESN by itself proved to be better than urea or a blend of the two.

“Thus, use of ESN either alone in longer-duration crops, and in blends with urea in short duration crops, could be encouraged, particularly in situations where environmental conditions promote N losses from denitrification and leaching,” Sahota says. “Farmers should recall that N losses are not affected to any large extent by soil pH, so your soil pH does not matter in this context, but N loss is generally greater at higher temperatures, not matter the source of N fertilizer.”

In terms of any temperature effects on yield itself, in the silage corn trials Sahota found that response to ESN did vary according to growing season temperature. In a normal year, there was no difference in dry matter yield from ESN or urea both applied at 150 kg N/ha. In a relatively colder year, however, ESN produced lower dry matter yield than urea, and in a warmer year, ESN gave significantly higher dry matter yield compared to urea. Sahota therefore feels that farmers in southern Ontario can use a urea:ESN blend closer to 1:2 instead of 2:1 because the N from ESN is likely to be more readily available in southern Ontario than it is in northern Ontario where he did his research.

In terms of spring or fall application, among other findings, Sahota observes that spring wheat yield was equal whether the ESN blend was applied in spring or fall, but protein was a little higher with spring application.

“I tried to trial as many different options as possible so that farmers can look at the results and choose what’s best for them,” he notes.

As a last word of advice, Sahota notes that ESN is best applied in the seed row at planting. “Because of the polymer coating,” he says, “it doesn’t damage the seedlings and N released in the seed row is quickly taken up by the roots.”

Readers are welcome to ask Dr. Tarlok Singh Sahota questions about this research. Email him at tssahota@lakeheadu.ca or call/text his cell at 807-707-1987.

Sahota’s paper can be found here:
www.davidpublisher.com/index.php/Home/Article/index?id=45024.html

Funding for this research was provided by Agrium, Northern Ontario Heritage Fund Corporation, and the Ontario Ministry of Agriculture, Food & Rural Affairs. •