@book{48788,
	author = {Ritchey, K. Dale.},
	title = {Potassium fertility in oxisols and ultisols of the humid tropics},
	publisher = {State College of Agriuclture and Life Sciences,},
	year = {1979},
	series = {Cornell International Agriculture. Bulletin},
	address = {Ithaca, New York :}
}