Freddie R. Lamm, Kansas State University, Northwest Research-Extension Center, Colby, Kansas, U.S.A. James E. Ayars, Agricultural Research Service, U.S., San Joaquin Valley Agricultural. Sciences Center, Panier. California, U.S.A. Francis S. Nakayama, Agricultural Research Service, U.S., Arid-Land Agricultural Research Center, Maricopa, Arizona, U.S.A.