Received for publication October 23, 1982. A contribution of the Georgia Agricultural Experiment Stations, College Station, Athens. This research was supported in part by State and Hatch funds allocated to the Georgia Agricultural Experiment Stations and by grant funds provided by Woolfolk Chemical Co., Fort Valley, Ga. The authors wish to acknowledge the excellent technical assistance of Andrew Tull during the duration of this research. 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.