AgWatch

N Management In Wet/Dry Years Requires Planning

MINER, MO.
   Information on managing nitrogen in wet and dry years was presented recently by Dr. Peter Scharf, nutrient management specialist with the University of Missouri.
   “We’ve had a sequence of years that stimulated that topic,” he began. “In 2011 we had one of the wettest years ever in southeast Missouri; 2012 was one of the dryest through the spring, and 2013 was back to the wet end again. This really creates some challenges and opportunities in nitrogen management.”
   He addressed some of the questions with data that has been collected.


Dr. Peter Scharf, nutrient management specialist with the University of Missouri
discusses the challenges in nutrient management in both wet years and dry years.

Photo by John LaRose, Jr.

   “Can you get away with all pre-plant nitrogen by using some of the forms that are resistant to nitrogen loss like anhydrous ammonia or ESN? The answer in a wet year is no,” he said. “Sidedress applications will out-yield those forms even though those forms will out-yield the other forms applied pre-plant.
   “Second question is ‘Do you need the pre-plant nitrogen at all?’ Our numbers say there has just not been a case identified where if we got a sidedress on at the regular time that the pre-plant added anything to yield. We’re getting no yield bump out of it.”
   In a few cases where the main application was delayed far into the season, having something on pre did protect from a yield loss with the delayed sidedress. The question is whether sidedress nitrogen can be lost, and the answer is in really wet years it can.
   “We have a couple of experiments showing that putting nitrogen on, the bulk of the nitrogen, at waist high in a really wet year actually outyielded putting it on at knee high,” he stated. “The only explanation that I can come up with for that is that some of the knee high applications got lost so I think it’s important to be on the lookout in a really wet year. The problem is corn is so tall it’s hard to see it; by the time it’s so tall, looking at it from an airplane is absolutely a fabulous way to do it. Here in Sikeston you can just go down to the airport, talk to the flight instructor and for a very reasonable price catch a flight, take your regular camera, take some pictures. If you see a problem you should do something.”
   Gene Stevens did some work showing late N applications on corn gave large yield responses where some stress was visible, but corn with no visible stress showed no yield response.
   “So you can pretty much tell by looking at it, and that exactly matches my experience,” Scharf said. “I’ve had farm experience with rescued nitrogen, corn that had been fully fertilized, with no intention of putting on more; but it looked stressed and when we put on more it yielded more. And the more stressed it looked the bigger the yield boost.”
   The last question is: How can farmers adjust nitrogen management in these really wet and dry years?
   “My thinking at this point is that if we get into a plan or commitment for management later into the season, that gives us more ability to flex with changes in weather,” he said. “By later in the season I’m talking  a planned application, hip higher or later would allow you to really flex that application up if it has been wet up to that point; and flex it down if you’re seeing that water is going to be limiting. That may not be the case too often, but my understanding is that in 2012 it was so hot and dry that the pivots couldn’t keep up.
   “So if you planned your last shot through the pivot or with a high clearance applicator or aerial application, that may influence your decision whether to reduce or eliminate that application because it was not going to be your yield limiting factor,” he advised. “The dry years another factor is that in furrow irrigated fields you may be pouring the water on and your distribution isn’t as even as it is in pivot; so you may end up having areas of the field where you’ve flushed your nitrogen out and you wind up with nitrogen deficiency just like it was a wet year. A later application will give you some protection against that in terms of protecting your full yield potential.
   “So to sum it up, you can’t get away with all pre-plant nitrogen in a wet year; yet sometimes you can’t even get away with regular time sidedress application in a wet year,” Scharf advised. “Go in with a planned later application to give you the ability to flex your rate up in a wet year, flex your rate down in a dry year if your system doesn’t allow you to provide all the water that the crop needs, and by doing that you will either increase yield or reduce input costs and increase total profitability.”∆
   BETTY VALLE GEGG-NAEGER: Senior Staff Writer, MidAmerica Farmer Grower


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