Fig. 4. Relationship between Mehlich-1 P and the degree of P saturation calculated using an oxalate extraction (DPS_Ox) for manure-impacted surface and subsurface soils from the middle Suwannee River basin. Horizontal dotted lines indicate agronomic high (30 mg P kg^–1) and very high (60 mg P kg^–1) soil test P concentrations in Florida (Kidder et al., 2002).