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

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 Me...

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Bibliographic Details
Published in:Water science and technology 2016-08, Vol.74 (3), p.691-697
Main Authors: Fischer, P, Pöthig, R, Gücker, B, Venohr, M
Format: Article
Language:English
Subjects:
Agricultural land
Agriculture
Brazil
Classification
Correlation analysis
Environmental Monitoring - methods
Environmental quality
Environmental science
Fertilizers
Fertilizers - analysis
Field tests
Hydroxides
Iron
Kinetics
Phosphorus
Phosphorus - chemistry
Risk Assessment
Risk factors
Runoff
Saturated soils
Saturation
Soil
Soil - chemistry
Soil investigations
Soil sciences
Soil surfaces
Soils
Sorption
Spatial variations
Studies
Surface runoff
Test methods
Water Movements
Water quality
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Summary: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.
ISSN:0273-1223
1996-9732
DOI:10.2166/wst.2016.169