The June 28 4R nitrogen stewardship tour looked at current research and tools that could be coming in the future
Increasing yields while applying the same or less nitrogen is good for farmers and the environment.
It also sums up the goal of the 4R stewardship program.
The four Rs refer to applying nitrogen to crops using the right source and rate at the right time and right place.
“That’s our big challenge,” University of Manitoba applied soil ecology professor, Mario Tenuta, said in an interview June 28 following a 4R tour attended by about 45 people, including farmers, researchers, students, crop consultants and fertilizer retailers. “It’s not easy to meet immediately. The 4Rs I like because it’s a framework to get this suite of practices to increase nitrogen use efficiency.”
Farmers are boosting yields partly by increasing nitrogen rates, but society won’t allow that to continue, Tenuta said during the tour. That’s because nitrogen not used by crops can be lost to the atmosphere, adding to greenhouse gas emissions, contributing to climate change, or leach and pollute water.
“Our research, and that of others, is saying with the 4Rs you get better nitrogen use (and) you can sustain or increase yields without increasing losses to the environment and decrease the negative environmental impact,” Tenuta said. “To keep it simple for farmers, use practices that use the 4R BMPs (best management practices). Worry about getting that nitrogen into your crop and if you can do that you are benefiting the environment.
“You are getting that benefit by increasing yields without increasing the nitrogen rates.”
The tour’s theme was present and future 4R nitrogen management. Research is revealing ways to increase nitrogen efficiency and technology will help farmers make it happen, Tenuta said.
For example, sensor-equipped high-clearance applicators can top up nitrogen in crop on the fly, based on what the crop needs, he said.
“That’s here today and I think it will probably be a big part of the future.”
The tour stopped at one of Carman farmer Tyler Russell’s cornfields, where operator Rod Owen applied liquid nitrogen (UAN) with a high-clearance applicator. Y-shaped hoses drop from the boom and are dragged along each corn row distributing liquid nitrogen.
At the V4 stage Owen applied 21 gallons of UAN, which is equivalent to about 60 pounds of nitrogen per acre. Depending on the crop, he will apply another 20 to 25 gallons just before tasselling.
Topping up nitrogen in corn crops is popular in the American Corn Belt where sometimes big rains this time of year rob the crop of nitrogen, Manitoba Agriculture soil fertility specialist John Heard told the tour.
“On these moist soils we can lose eight to 16 pounds of nitrogen a day,” he said. “The guys in Missouri found they were just leaving way too much yield on the table. If they could still come back and supplement it was rewarding. We don’t know if we have enough season (in Manitoba) yet to correct those in-season deficiencies.”
Heard is running trials to find out.
Researchers already know that corn, being a longer-maturing crop, needs nitrogen for much longer during the growing season than wheat.
Heard suggested nitrogen-release inhibitors might help protect against early-season nitrogen losses in corn.
Owen said he travels between eight and 8.5 miles per hour when applying the nitrogen in crop.
“If you start getting up into that 10-mile-an-hour (range) it whips that V4 corn around pretty good,” he said.
At the same stop Adam McKnight with Bud McKnight Seeds discussed a portable soil nutrient analysis machine about the size of a suitcase. The company is testing its accuracy.
“We really want to prove that it’s accurate before we start running with it,” McKnight said. “That’s why we haven’t been talking about it a ton yet. We really want to field test it first.”
Technology that can speed up nutrient analysis and do it cheaper is a good thing, Tenuta said later. However, he noted representative samples are needed for good test results.
John Lee, a soil scientist with North Dakota soil testing lab AgVise, also said the machine must be properly calibrated and samples properly prepared.
The tour also heard about research into developing nitrogen recommendations for higher-yielding spring wheats being conducted by Amy Mangin, a University of Manitoba research associate.
The current recommendation of applying 2.5 pounds of nitrogen per acre for every target bushel of yield, isn’t practical with wheats yielding 80 to 100 bushels an acre, she said.
The three-year study is using Brandon and Prosper, which are in the Canada Western Red Spring and Canadian Northern Hard Red classes, respectively.
Data from 2016 showed when the same amount of nitrogen was applied, Prosper consistently outyielded Brandon by eight to 14 bushels an acre. However, Brandon consistently had 0.1 to 2.2 per cent more protein than Prosper.
Mangin is also looking at the impact of when various amounts of nitrogen are applied post-anthesis and investigating possible tools to determine if the crop has enough nitrogen to meet its needs and to estimate the mineralization of organic nitrogen.
Under ideal growing conditions sometimes there’s enough residual nitrogen to meet the crop’s needs without having to apply more, Heard said.
Weather, especially moisture, plays a big role in nitrogen availability.
“But there are probably some factors in there that we can predict that are part of the mixture contributing to nitrogen mineralization based on the organic matter in the soil… and what is easily mineralizable in the course of the growing season,” he said.
Factors include the presence of soil organisms and the amount and type of residual left by the previous crop.
“There is always going to be a problem with weather impacts,” Tenuta said. “If we can tease out the weather versus the cultural management practices such as the previous crop and residue management of that crop I think we’ll go a long way in predicting more refinement in how much nitrogen is going to be available in a crop year. Right now it’s a big uncertainty…”