Top dressing winter wheat with nitrogen fertilizer will usually increase the yield. We found this out in 19 field trials we made in the major wheat growing area in western Iowa. Nitrogen fertilizer raised yields 6 1/2 to 12 bushels an acre on 4 out of every 5 of the fields tested. And the top-dressing produced a better quality wheat- a wheat higher in protein.
Nelson, L. B. and Pritchett, W. L.
"Nitrogen Helps Winter Wheat,"
Iowa Farm Science: Vol. 3
, Article 3.
Available at: https://lib.dr.iastate.edu/farmscience/vol3/iss3/3