Taxonomic and Geographic Distribution of Total Phosphorus in Florida Surface Soils

Taxonomic and geographic distributions of background P concentration in soils are important when Taxonomic and geographic distributions of background P concendeciding whether a site is influenced by anthropogenic trations are important in assessing whether a soil P level is influenced by anthropogenic activities. This study was conducted to establish an input of P. Knowledge of background concentration and upper baseline concentration (UBC) of soil P, which is defined as its variation in soils helps address issues such as the 97.5% of the background concentration, using 448 geographically and effects of past land-use practices on P levels in soils and pedogenically representative Florida surface soils (genetic horizon A, establishing proper limits when conducting risk assessA1, Ap, O, O1 or Op) using total P as determined by the USEPA ments for P eutrophication in water systems. Upper Method 3052 (HCl–HNO3–HF digestion). A significant difference baseline concentration, which is defined as the upper existed in total P concentrations between disturbed (126 mg kg 1, 97.5% and calculated as the GM multiplied by the n 180) and undisturbed (60 mg kg 1, n 268) soils. Geometric square of geometric standard deviations (GSD) of the mean (GM) concentration of total P in the undisturbed soils decreased expected range of background concentration, has been in the order of Histosols (350 mg kg 1 ) Mollisols (171 mg kg 1 ), used in several studies to assess changes in elemental 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 compositions (Gough et al., 1994; Dudka, 1995; Chen suborders tended to have greater P contents than the dry suborders, et al., 1999b). Chen et al. (1999a) reported that soil e.g., Aquents (92 mg kg 1 ) Psamments (47 mg kg 1 ) and Aquods UBC of total P equals 1374 mg kg 1 and could be used (27 mg kg 1 ) Orthods (14 mg kg 1 ). Total P estimation based on as a reference level for assessing potential nonpoint digitized taxonomic soil maps suggested that native soil properties sources of P enrichment in Florida soils. However, no were primary factors in controlling total P in soils. The wide occurdetailed information is available on how this informarence of P bearing parent materials resulted in many soils having high tion can be applied to different land uses and soil P concentrations. Twenty-four P-elevated samples from the disturbed category. soils were identified using the UBC of P for the undisturbed soils at At the state level, Florida showed the most striking suborder level as reference criterion. Anthropogenic P inputs were pattern by having low soil background concentrations related to commercial PO4–fertilizer application and population growth as nonpoint sources. of most elements in the U.S. A few soil samples with high P were associated with PO4 deposits in Florida (Shacklette and Boerngen, 1984). In southern Florida, however, P has been considered the element that most P is a major nutrient essential for plant threatens the overall health of lakes and the critical growth. Fertilizer application of P and other nutrilevel of dissolved P allowable in drainage water entering ents has contributed more than any other measure to the Everglades is currently being debated (McPherson increasing crop productivity in agriculture. However, and Halley, 1996). A large, rapidly growing population overabundance of P in the nation’s waters and soils has in the coastal peninsula region and in central Florida become a major environmental concern (Muller et al., since the 1970s continues to impact the Florida environ1995; Daniel et al., 1998). Transportation of soluble and ment via elevated N and P levels in soils (McPherson soil-bound P influences soil fertility strategies and can and Halley, 1996). Intensive cattle ranching and farming accelerate eutrophication in lakes and streams suris another nonpoint source of nutrients that can elevate rounding agricultural areas. Knowing the P status of soil P concentration because of the lack of economically soils is important for developing an effective P-manageviable alternatives for manure disposal (Harris et al, ment strategy (Chen et al., 1999a; Higgs et al., 2000). 1994; Maluk et al., 1998; Sharpley et al., 1996). Field Numerous studies on P assessment focused on plantstudies have shown that dissolved P concentrations in available soil P tests (Sharpley et al., 1996; Daniel et runoff were related to total P in surface soils (Sharpley al., 1998; Higgs et al., 2000). Assessment criteria based et al., 1996). Little is known about taxonomic and geoon total soil P are, however, not emphasized in the litgraphic distributions of P background concentrations in erature. Florida surface soils. M. Chen, Institute of Geography and Natural Resources, Chinese The objectives of this research were (i) to establish Academy of Sciences, Beijing 100101, China; L.Q. Ma, Soil and Water natural and anthropogenic background concentrations Science Dept., University of Florida, Gainesville, FL 32611-0290. Apof total P in Florida surface soils; (ii) to determine taxoproved for publication as Florida Agricultural Experiment Station Journal Series No. R-06744. Received 28 Sept. 2000* Corresponding Abbreviations: GM, geometric mean; GSD, geometric standard deviaauthor ([email protected]). tion; muid, map unit identifier; STATSGO, state soil geographic database; UBC, upper baseline concentration. Published in Soil Sci. Soc. Am. J. 65:1539–1547 (2001).