Received for publication December 12, 1973, authorized for publication as paper No. 4593 in the journal series of the Pennsylvania Agricultural Experiment Station, University Park. Part of a thesis submitted by the senior author in partial fulfillment for the Ph.D. degree, The Pennsylvania State University, June 1973.
Present address, Goddard Space Flight Center, Code 430.6 Glendale Building #3 (G.E.), Greenbelt, MD.
Professors of Plant Nutrition, Department of Horticulture and of Plant Pathology, Department of Plant Pathology, respectively.