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Degree of phosphorus saturation threshold for minimizing P losses by runoff in cropland soils of Southern Brazil

2016; Embrapa Informação Tecnológica; Volume: 51; Issue: 9 Linguagem: Inglês

10.1590/s0100-204x2016000900008

1678-3921

Leandro Bortolon, Paulo Roberto Ernani, E. S. O. Bortolon, Clésio Gianello, Rodrigo Gabriel Oliveira de Almeida, Samuel Welter, Douglas Antônio Rogeri,

Soil erosion and sediment transport

Abstract The objective of this work was to assess the risk of phosphorus losses by runoff through an index based on the degree of P saturation (DPS), in cropland soils of Southern Brazil. Sixty-five highly representative cropland soils from the region were evaluated. Three labile P forms were measured (Mehlich-1, Mehlich-3, and ammonium oxalate), and four P sorption indexes were tested (phosphorus single sorption point and Fe+Al determined with the three extractors). Water-extractable P (WEP) was used as an index of P susceptibility to losses by surface runoff. The DPS was determined from the ratio between labile P and each sorption index. DPS values obtained from the ratio between Mehlich-1 P and the single P sorption point ranged from 1 to 25%, whereas those from Mehlich-1 P and Fe+Al (ammonium oxalate) ranged from 1 to 55%. All DPS types were highly correlated with WEP. From a practical stand point, the DPS obtained with both P and Fe+Al extracted with Mehlich-1 can be used to estimate the risk of P losses by runoff in soils of Southern Brazil.