Reaching the target soil phosphorus concentration zone for optimum crop
yields and limited P losses to water
Amery Fien1,Vandecasteele Bart1
1
Institute for Agricultural and Fisheries Research
Plant Sciences Unit - Crop husbandry and environment
Burg. van Gansberghelaan 109, Merelbeke, Belgium
Fien.Amery@ilvo.vlaanderen.be
A review study aimed to merge knowledge and legislation on phosphorus (P) in Europe in order to
distill guidelines for measures to reduce phosphorus losses from agriculture to surface waters.
Phosphorus (P) concentrations in European surface waters generally exceed ecological thresholds.
The Nitrates Directive and the Water Framework Directive ask of the Member states to tackle this
phosphorus problem. Resulting monitoring networks and P concentration standards differ, however,
widely between Member states. Since agriculture is considered to have a large impact on the surface
water P concentrations, the diffuse P losses from soils with high P contents are targeted. It is
attempted to reduce the soil P concentration under the threshold above which P losses increase
exponentially (dashed line in figure 1). However, also agro-economical interests should be taken into
account. Farmers are reluctant to reduce P fertilization since they fear reduced soil P concentrations
resulting in reduced crop yields and quality (solid line in figure 1). A target zone of soil P
concentrations with optimum crop yields and limited P losses can be defined (grey zone in figure 1).
In order to reach or stay in this target zone, fertilisation recommendations should be adapted to also
include the risk for P losses. Soil P application standards are ideally differentiated to soil P
concentrations. In this way, soils with large P concentrations must receive less P in order to reduce
the P losses (movement from the right-hand side of figure 1 towards the target zone) and soils with
small P concentrations can receive more P to ensure satisfactory crop yields (movement from the
left-hand side of figure 1 towards the target zone).
Figure 1
Crop yield (solid line) and soil P loss (dashed line) vary with increasing soil P concentration. A
target zone with optimum yields and limited P losses is defined.