Research Support Specialist, Dept. of Horticultural Sciences
Research Chemist, ARS/USDA, U.S. Plant, Soil, and Nutrition Laboratory, Ithaca, NY 14853.
Received for publication 1 Feb. 1988. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.