Received for publication April 23, 1970. The investigation reported in this paper (No. 70-10-41) is part of a project of the Kentucky Agricultural Experiment Station and is published with approval of the Director.
Associate Professor of Horticulture.
The authors wish to thank Dr. R. F. Carlson, Horticultural Department, Michigan State University, East Lansing, for advice given when this experiment was started. Thanks are also due to Dr. J. C. Williams, Agronomy Department, University of Kentucky, for statistical and computing advice and to Mrs. E. Duff for technical assistance.