Taxonomic and Geographic Distribution of Total Phosphorus in Florida Surface Soils

Taxonomic and geographic distributions of background P concentrations are important in assessing whether a soil P level is influenced by anthropogenic activities. This study was conducted to establish an upper baseline concentration (UBC) of soil P, which is defined as 97.5% of the background concentration, using 448 geographically and pedogenically representative Florida surface soils (genetic horizon A, A1, Ap, O, O1 or Op) using total P as determined by the USEPA Method 3052 (HCl–HNO 3 –HF digestion). A significant difference existed in total P concentrations between disturbed (126 mg kg −1 , n = 180) and undisturbed (60 mg kg −1 , n = 268) soils. Geometric mean (GM) concentration of total P in the undisturbed soils decreased in the order of Histosols (350 mg kg −1 ) > Mollisols (171 mg kg −1 ), Inceptisols (140 mg kg −1 ) > Ultisols (88 mg kg −1 ) > Alfisols (54 mg kg −1 ), Entisols (53 mg kg −1 ) > Spodosols (24 mg kg −1 ). Aquic suborders tended to have greater P contents than the dry suborders, e.g., Aquents (92 mg kg −1 ) > Psamments (47 mg kg −1 ) and Aquods (27 mg kg −1 ) > Orthods (14 mg kg −1 ). Total P estimation based on digitized taxonomic soil maps suggested that native soil properties were primary factors in controlling total P in soils. The wide occurrence of P bearing parent materials resulted in many soils having high P concentrations. Twenty‐four P‐elevated samples from the disturbed soils were identified using the UBC of P for the undisturbed soils at suborder level as reference criterion. Anthropogenic P inputs were related to commercial PO 4 –fertilizer application and population growth as nonpoint sources.