Cropside: UAN, streamer nozzles, leaf burn and corn yield

QUESTION
Growers seeking high speed N application after the planting window has past are turning increasingly to high capacity sprayers and streamer nozzles to apply UAN “over the top”.  One of the biggest concerns is leaf burn when the UAN hits the corn leaves.  Does leaf burn from UAN cause significant yield impacts?  Clearly leaf burn seems to be quite minor at younger stages but at the eight leaf stage it can look ugly.  The photos capture eight leaf corn at three, six and nine days after application.  The leaf injury clears quite quickly.

PHOTO: INJURY FROM UAN APPLIED WITH STREAMER NOZZLES AT 33 GAL/AC OVER THE CORN CANOPY AT THE 8 LEAF STAGE AS EVIDENT 3 DAYS AFTER APPLICATION.

PHOTO:  INJURY FROM UAN APPLIED WITH STREAMER NOZZLES AT 33 GAL/AC OVER THE CORN CANOPY AT THE 8 LEAF STAGE AS EVIDENT 6 DAYS AFTER APPLICATION.

PHOTO: INJURY FROM UAN APPLIED WITH STREAMER NOZZLES AT 33 GAL/AC OVER THE CORN CANOPY AT THE 8 LEAF STAGE AS EVIDENT 9 DAYS AFTER APPLICATION.

FINDINGS
Table 1 summarizes 2013 data where N application options where tested: 1) Control, 150-180 lbs N/acre  injected at planting, 2) N Soil, same planting N plus UAN directed below the canopy to the soil surface and 3) N Streamer, same planting N plus UAN applied with streamer nozzles over the canopy.  4 leaf stage yields were not significantly different among all three options suggesting that planting N was sufficient for maximum yields and that the burn associated with 4 leaf corn streamers did not have a negative impact on yield.  At later growth stages there is a trend for the UAN directed below the canopy to have higher yields than when the UAN was applied with streamers.  At these later leaf stages streamer nozzle applications may be associated with some yield reducing leaf injury and/or less N availability.

Post Emergent UAN Application Method:	Yield (bu/ac) for given application timing
	4 Leaf	8 Leaf	10 Leaf
Control (no post emergent application)	179 A	179 B	179 AB
N Soil (100 lb-N/ac directed below canopy)	184 A	191 A	185 A
N Streamer (100 lb-N/ac streamer)	176 A	179 B	168 B

Greg Stewart collaborated with Ian McDonald (OMAF and MRA) and Ben Rosser (University of Guelph) on this research. •