Background, aim, and scope Phosphorus loss from terrestrial
to the aquatic ecosystems contributes to eutrophication of
surface waters. To maintain the world's vital freshwater
ecosystems, the reduction of eutrophication is crucial. This
needs the prevention of overfertilization of agricultural soils
with phosphorus. However, the methods of risk assessment
for the P loss potential from soils lack uniformity and
are difficult for routine analysis. Therefore, the efficient
detection of areas with a high risk of P loss requires a simple
and universal soil test method that is cost effective and
applicable in both industrialized and developing countries.
Materials and methods Soils from areas which varied
highly in land use and soil type were investigated regarding
the degree of P saturation (DPS) as well as the equilibrium
P concentration (EPC0) and water-soluble P (WSP) as
indicators for the potential of P loss. The parameters DPS
and EPC0 were determined from P sorption isotherms.
Results Our investigation of more than 400 soil samples
revealed coherent relationships between DPS and EPC0 as
well as WSP. The complex parameter DPS, characterizing
the actual P status of soil, is accessible from a simple
standard measurement of WSP based on the equation
DPSð%Þ ¼ 1
Discussion The parameter WSP in this equation is a
function of remaining phosphorous sorption capacity/total
accumulated phosphorous (SP/TP). This quotient is independent
of soil type due to the mutual compensation of the
factors SP and TP. Thus, the relationship between DPS and
WSP is also independent of soil type.
Conclusions The degree of P saturation, which reflects the
actual state of P fertilization of soil, can be calculated from the
easily accessible parameter WSP. Due to the independence
from soil type and land use, the relation is valid for all soils.
Values of WSP, which exceed 5 mg P/kg soil, signalize a
P saturation between 70% and 80% and thus a high risk of P
loss from soil.
Recommendations and perspectives These results reveal a
new approach of risk assessment for P loss from soils to
surface and ground waters. The consequent application of
this method may globally help to save the vital resources of
our terrestrial and aquatic ecosystems.