ESN? Urea? A blend? Which is best for your crops?
That may depend where you live.
ESN is a polymer-coated urea product that releases the fertilizer over time, and new research suggests local matters when it comes to using it.
“Once (ESN) is put into the soil, water moves into the granule, dissolves the nitrogen and it is released into the soil,” Alberta Agriculture’s Len Kryzanowski told the recent Agronomy Update event in Red Deer.
“This is very heavily dependent on temperature and moisture, which are the same conditions that affect crop growth. In theory, it should sync the availability of the nitrogen with the crop demands.”
But does it?
That was one of the key questions of a four-year study that sought to evaluate urea, ESN and a blend based on crop growth and yield. Researchers wanted to discover the optimal situation for the use of each fertilizer, based on spring or fall applications, moisture conditions and crop. They also wanted to determine the best regions for use of the three products as well as agronomic rate limits for ESN and urea to reduce seedling damage.
Researchers compared ESN, urea and a blend of 25 per cent urea and 75 per cent ESN, fall versus spring application, and banding versus seed placement. Wheat, barley and canola were used throughout the study. Fertilizer was applied at rates of zero, 30, 60, 90 and 120.
“You’ve got quite a complex design of treatments, but these are the common decisions that a farmer will have to make when he is using fertilizer products, so it makes sense to do these comparisons,” said Kryzanowski.
There were nine research sites (Beaverlodge, Barrhead, Bow Island, Lacombe, Vegreville, High River, Gibbons and Lethbridge — irrigated and dryland) and all were continuously cropped or stubble fields. Researchers tracked dates for heading, emergence, maturity, and plant counts at the two-leaf stage. After harvest, factors such as per cent grain moisture content, grain yield, weight, thousand kernel weight and kernel plumpness were analyzed. Soil and precipitation information was also collected, and the nitrogen left after cropping was measured to gauge the potential for leaching.
“High River was a high-moisture situation,” Kryzanowski said. “You got an excellent response to added fertilizer, whether it was ESN or urea. There were some indications that there was some damage to the crop, especially the wheat with seed-placed urea.
“In comparison, Beaverlodge had drier conditions, much lower yields, and the response to added fertilizer was in the opposite direction. As you increased the fertilizer, the yields were starting to go down. We’re starting to see less response for fertilizer application for all three crops.”
In moist conditions, protein levels in the grain and seed were found to increase with the addition of fertilizers.
“In some cases, you could see better responses with urea and fall-banded versus spring and fall applications,” said Kryzanowski. “You have a whole mixture of responses that are occurring here. That’s the challenge in trying to sort out the information.”
Beaverlodge, with its low moisture, showed higher levels of grain protein than High River. “Even though you have lower moisture conditions, your response in regards to the protein level is actually increasing,” he said.
Seed-placed urea product caused seedling damage and decreases in plant population at the High River site. However, this did not cause a reduction in yield, indicating the ability of the crops to compensate for the loss.
Beaverlodge showed a greater rate of seedling damage, particularly when urea was seed placed next to canola.
“This also reflected low productivity” said Kryzanowski. “We’re below the threshold in terms of having an adequate amount of plant population to grow a sustainable yield. One of our challenges is going to be to identify these thresholds in terms of plant numbers, populations, and product.”
There was a significant yield response to nitrogen from the majority of sites and crops and significant protein response and nitrogen rate for all southern sites and crops. Yield and protein response to fertilizer varied by region and crop. Seed-placed urea caused the greatest seedling damage to wheat and canola, followed by barley. Blending ESN and urea allowed for good nitrogen rates without seedling damage for most of the sites. Seed-placed ESN allowed for high rates of nitrogen to be applied with the crop and banding with ESN maximized the slow, gradual nitrogen release.
The bottom line
Researchers completed a simple economic analysis to compare the various treatments.
“What we found was about 40 per cent of the time, you’ll see an economic response on barley and wheat when you use ESN,” Kryzanowski said. “Canola is a bit better and you’ll see an economic benefit about 60 per cent of the time.”
Rates and benefits vary by different areas of the province.
“Variation between sites, in sites and among sites was high and there was some indication of regional differences,” Kryzanowski said.
The variability of response makes it hard for researchers to determine or predict best products or applications.
“We have a big challenge ahead of us in terms of trying to use this information,” he said.
Since ESN is a slow-release fertilizer, it has the ability to reduce nitrate emissions and minimize leaching. N2O emissions varied greatly during the year. Spring thaw is a critical time in terms of nitrous oxide loss.
“Any time we have fall fertilizer application, we’re going to see high N2O emissions coming off in the springtime,” Kryzanowski said.
Going from a fall urea to a spring urea resulted in a reduction of 65 per cent of nitrous oxide emissions, and going from fall urea to spring ESN also greatly reduced emissions.