Broadcast postemerge application of urea-ammonium nitrate solution (28 and 32 percent UAN) to corn has the potential to cause phytotoxic symptoms of leaf burn, necrosis, loss of leaves, and plant stunting. Burn symptoms will be visible within 24 to 48 hours after application. With hot-dry conditions, appearance of darkened leaf tissue can begin within a few hours. Depending upon the severity of damage, reduced plant growth may be visible for several weeks after application.
Iowa State University
Sawyer, John E., "Watch for damage from broadcast postemerge UAN applications" (2001). Integrated Crop Management News. 1988.
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