title: Estimation of the degree of soil P saturation from Brazilian Mehlich-1 P data and field investigations on P losses from agricultural sites in Minas Gerais.
abstract: The degree of phosphorus saturation (DPS) of agricultural soils is studied worldwide for risk assessment of phosphorus (P) losses. In previous studies, DPS could be reliably estimated from water-soluble P (WSP) for European and Brazilian soils. In the present study, we correlated measured WSP and Mehlich-1 P (M1P) from soils of Minas Gerais (MG) and Pernambuco (PE) (R(2) = 0.94, n = 59) to create a DPS map from monitoring data. The resulting DPS map showed high spatial variability and low values of DPS (54 ± 22%, mean and standard deviation; n = 1,827). Measured soil DPS values amounted to 63 ± 14% and resulted in relatively low dissolved P concentrations measured in a surface runoff study in MG. However, fertilizer grains on the soil surface led to high WSP values (>30 mg/kg) indicating high risks of dissolved P losses. We suppose that small Oxisol particles with Fe and Al hydroxides sorbed most of the dissolved fertilizer P in runoff so that P was mainly exported in particulate form. In soils with lower contents of P sorption and binding partners, e.g. Entisols in PE, this effect may be less dominant. Consequently, superficial fertilizer effects have to be considered in addition to DPS in risk assessment of P losses from agricultural areas in Brazil.
authors: Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Justus von Liebig Straße 7, Berlin 12489, Germany E-mail: peter_fischer@online.de; Geography Department, Humboldt-University Berlin, Unter den Linden 6, Berlin 10099, Germany.
authors: P
authors: P
authors: Fischer
authors: Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Justus von Liebig Straße 7, Berlin 12489, Germany E-mail: peter_fischer@online.de.
authors: R
authors: R
authors: Pöthig
authors: Department of Geosciences, Federal University of São João del-Rei, Campus Tancredo Neves, R. Visconde do Rio Preto s/n, São João del-Rei, MG, Brazil.
authors: B
authors: B
authors: Gücker
authors: Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Justus von Liebig Straße 7, Berlin 12489, Germany E-mail: peter_fischer@online.de.
authors: M
authors: M
authors: Venohr
mesh_terms: D000383:Agriculture; D001938:Brazil; D004784:Environmental Monitoring / Q000379:methods; D005308:Fertilizers / Q000032:analysis*; D007700:Kinetics; D010758:Phosphorus / Q000737:chemistry*; D018570:Risk Assessment; D012987:Soil / Q000737:chemistry*; D014872:Water Movements
chemical_list: D005308:Fertilizers; D012987:Soil; D010758:Phosphorus