What is in this article?:
- Weather extremes challenge corn nitrogen management
- Move toward spring applications, but see a bigger picture
- Extreme rain events cut profits
- N-decision model boosts savings
- Fall N application advice
N risk management advice in a nutshell:
- Time in-ground and wild, wet springs reduce N availability.
- Delay N applications on lighter soils until spring.
- Don’t count on one-time fall-applied or even early spring-applied N to be there when and where corn needs it.
- Get more efficient N use by piggybacking N application with other field trips—apply N in as many operations as you can.
- Sidedress as soon as you can.
- Save N adjustments until final sidedress, then apply according to soil tests.
- Don’t fall-apply N on high-pH soils.
Move toward spring applications, but see a bigger picture
“Getting the crop in the ground during the optimum spring planting window is the most significant of any of the risks,” says Frieberg, who has the benefit of reviewing precision ag production data from farms across the Midwest. “Too often in the real world, Mother Nature gives us only 10 to 15 days fit for field operations in that optimum planting window and you don’t want to be caught missing an optimum planting day because you’re taking that day to apply nitrogen. 2013 is going to be a dramatic example of just how important it is to plant when it’s fit—in the Upper Midwest, we’ll have more of the world’s most productive fields that didn’t get planted to a crop than any time I can remember.”
. Beyond yield loss for late planting, it’s important to factor in the potential cost of drying corn if planting is delayed too long.Still, Frieberg’s recommendation is to delay N applications on lighter soils until spring, and on well-drained heavy soils, fall-apply no more than 60% of total expected N needed as anhydrous ammonia with an N inhibitor.
“Nitrogen management has so many variables across the Corn Belt that it’s misleading to make recommendations that apply across the board. But in general, my strategy would be to save your N adjustments until spring,” Frieberg advises. “It’s still a guess then, but in the fall, it’s a total guess. You can apply more nitrogen preplant, at planting, or as sidedress. Sidedress as soon as possible—don’t wait until the week corn will close the row. If you split hairs over sidedress timing, the weather could shut you out again.”
Waiting until spring to apply N is pretty much a given for most of independent crop consultant Damon Winterrowd’s clients.
“We have very little fall N application in our area, CropStar crop consultant Winterrowd says. “Late June and July is a high nitrogen demand period for corn—even if you put it all on before planting in April a lot of things can happen to that N. You want to know the N is there when the plant is growing—not just hope it’s going to be available.”
So Winterrowd’s first discussion with growers involves avoiding single applications. “You spread your risk if you make as many applications of N as you can, with other field operations. Put some on preplant, apply some with the planter, maybe mix some with herbicides—the more applications you can make, the better,” Winterrowd says. “Then use tests like the late spring nitrate soil test to analyze remaining needs, and make adjustments at your final sidedress.” Winterrowd also recommends trying two N stabilization products, and testing their effectiveness through yield comparisons and cornstalk nitrate tests.
The University of Minnesota has a time-tested, simple decision tool Vetsch says can be used in lieu of late-spring soil N tests to estimate N losses and guide decisions on supplemental N needs as sidedress. The guide uses a point system with multiple-choice answers to these three questions:
1) When was the fertilizer N applied?
2) What was the predominant May soil moisture condition?
3) How does the corn look today?
The answers to the questions result in points that either recommends sidedressing at 40-70 pounds of N/acre, recalculating in a few days, or applying no additional N. See the worksheet online.
N losses from weather conditions are highly variable, but you can limit your N risk. This chart shows that at 60 cents a pound, a fall N application could cost you more than $60 an acre if you lose 75% of 140 pounds per acre applied in the fall in a worst-case scenario. Split applications cut the risk.