Nitrogen management and the complexities of the 4Rs

With the arrival of the 2016 growing season comes questions about how to best manage nitrogen (N). This annually vexing problem never seems to get any easier because there are so many moving parts to the complex decisions regarding the 4Rs (Right place, Right time, Right rate, Right source) and N.

“I think we sometimes overlook that this is a very complicated system. The performance objective of N management is really important to consider. Is the goal to maximize yield, maximize economic return or minimize environmental loss? Sometimes these things do not go hand in hand,” said Josh McGrath, soil extension specialist with the University of Kentucky. “Sometimes we want to put out a positive story that if we minimize environmental loss, we also maximize economic return. That is not always the case. Sometimes you have to pick one as more important than the other. When you are at the economic optimum, your N losses might be higher than if you are taking an economic loss. Some of that has to do with the complexity of determining what the right rate really is. Sometimes even our best effort with N is still not going to be good enough.”

In the end, the general focus needs to be on maintaining farm profitability with regard to N management and the 4Rs.

“In general, I think folks are doing the best they can to maintain farm profitability, and that is necessary,” McGrath said. “Profitable farms can invest in more conservation practices. If we need to do better than what we are doing now environmentally, we need new technology and we need to invest in new methods in picking the right N rate, applying N to minimize the environmental impact, and we need to invest in developing new ideas about N management.”

The immediate focus with improving N management should probably be on the timing of the applications, McGrath said.

“The most important R without a doubt with N management is the right time. Timing is the one R we can best control. If we have the rest pretty good — if we are following good recommendations on our rate and we are placing it appropriately — timing is the low hanging fruit. Split applying or spoon-feeding to the crop is always going to increase efficiency and it is going to make you a smarter N manager because you’ve got more climate history behind you. You can adjust to what the weather has been,” McGrath said. “I think we also have to do a better job of adjusting our N rate for variability of what our N requirement is in space and time.”

There are currently some tools to help improve the accuracy of rate decisions.

“Some of the tools out there are the N sensors — GreenSeeker, OptRx or N Sensor are the three sensors on the market,” he said. “They can help us dial in that sidedress rate on the corn or the topdress on the wheat and do spatially variable applications and try and address the variability in N requirements. I think that now shows the most promise moving forward as far tools that are available out there.”

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