Fact Sheet No. 225, UMaine Extension No. 2094 Prepared by David E. Yarborough, Extension Blueberry Specialist, and John M. Smagula, Emeritus Professor of Horticulture, The University of Maine, Orono, ME 04469. Revised January 2013. Introduction Before preemergence herbicides were available blueberry fields were fertilized with only small amounts of nitrogen fertilizer.  Growers didn’t want to