Phosphorus saturation and superficial fertilizer application as key parameters to assess the risk of diffuse phosphorus losses from agricultural soils in Brazil

P Fischer; R Pöthig; B Gücker; M Venohr

doi:10.1016/j.scitotenv.2018.02.070

Phosphorus saturation and superficial fertilizer application as key parameters to assess the risk of diffuse phosphorus losses from agricultural soils in Brazil

Sci Total Environ. 2018 Jul 15:630:1515-1527. doi: 10.1016/j.scitotenv.2018.02.070. Epub 2018 Mar 7.

Authors

P Fischer¹, R Pöthig², B Gücker³, M Venohr⁴

Affiliations

¹ Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Department of Ecohydrology, Justus von Liebig Straße 7, 12489 Berlin, Germany; Humboldt-University Berlin, Geography Department, Unter den Linden 6, 10099 Berlin, Germany. Electronic address: peter_fischer@online.de.
² Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Department of Ecohydrology, Justus von Liebig Straße 7, 12489 Berlin, Germany. Electronic address: r.poethig@gmx.net.
³ Federal University of São João del-Rei, Department of Geosciences, Campus Tancredo Neves, 36301-360 São João del-Rei, MG, Brazil. Electronic address: guecker@ufsj.edu.br.
⁴ Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Department of Ecohydrology, Justus von Liebig Straße 7, 12489 Berlin, Germany. Electronic address: m.venohr@igb-berlin.de.

PMID: 29554769
DOI: 10.1016/j.scitotenv.2018.02.070

Abstract

In Brazil, a steady increase in phosphorus (P) fertilizer application and agricultural intensification has been reported for recent decades. The concomitant P accumulation in soils potentially threatens surface water bodies with eutrophication through diffuse P losses. Here, we demonstrated the applicability of a soil type-independent approach for estimating the degree of P saturation (DPS; a risk parameter of P loss) by a standard method of water-soluble phosphorus (WSP) for two major soil types (Oxisols, Entisols) of the São Francisco catchment in Brazil. Subsequently, soil Mehlich-1P (M1P) levels recommended by Brazilian agricultural institutions were transformed into DPS values. Recommended M1P values for optimal agronomic production corresponded to DPS values below critical thresholds of high risks of P losses (DPS=80%) for major crops of the catchment. Higher risks of reaching critical DPS values due to P accumulation were found for Entisols due to their total sorption capacities being only half those of Oxisols. For complementary information on soil mineralogy and its influence on P sorption and P binding forms, Fourier transformation infrared (FTIR) spectroscopic analyses were executed. FTIR analyses suggested the occurrence of the clay minerals palygorskite and sepiolite in some of the analyzed Entisols and the formation of crandallite as the soil specific P binding form in the investigated Oxisols. Palygorskite and sepiolite can enhance P solubility and hence the risk of P losses. In contrast, the reshaping of superphosphate grains into crandallite may explain the chemical processes leading to previously observed low dissolved P concentrations in surface runoff from Oxisols. To prevent high risk of P losses, we recommend avoiding superficial fertilizer application and establishing environmental thresholds for soil M1P based on DPS. These measures could help to prevent eutrophication of naturally oligotrophic surface waters, and subsequent adverse effects on biodiversity and ecosystem function.

Keywords: Crandallite; Degree of phosphorus saturation; Eutrophication; FTIR spectroscopy; Mehlich-1; Palygorskite; Soil fertility classes.