Sugarbeets (Beta vulgaris L.) have been fertilized with phosphorus (P) in the U.S.A. for the past 30 to 40 years. During this period, numerous studies on P fertilization rates and application methods have been conducted. Much of this information has been summarized (12, 14, 15, 4). Recent soil test data from England and the U.S.A. suggest that the available P levels in many soils are sufficient for maximum root and sucrose production without P fertilization. Detrimental effects of P fertilization at excessive soil P levels have been reported (6, 5) but not all data support these conclusions (12). Increasing fertilizer costs have also made it essential that growers have adequate guidelines upon which to base fertilizer applications. Information has been limited in Idaho for establishing an adequate soil test P level for optimum sugarbeet production. With this as background, we conducted two field experiments evaluating 1) the P fertilizer requirements of sugarbeets at different soil test P levels, and 2) the effects of P fertilization on soils already containing adequate available P levels.