The agricultural and environmental consequences of the change in the classification of phosphate categories are mapped in this project.
In the fourth Dutch action program within the framework of the Nitrates Directive, phosphorus use from fertilisers, manures and soil amendments depends of the phosphorus status of agricultural land. The phosphorus use standards in the action plan is differentiated according to soil P status wchich is divided into three classes, 'low', 'neutral' and 'high'. The boundaries between these classes are based policy considerations and phosphorus fertiliser recommendations based on soil testing. As part of the fifth action program the boundary between the class low and neutral might be set at a lower value in order to adapt with the classification of soil phosphorus in current fertiliser recommendations. The agricultural and environmental implications of lowering the limits of a soil P class for the area culture land involved, the implication and perspectives for an agronomic and environmentally sound use of manure and development of the soil phosphorus status on the long term are not sufficiently known. The goal of this project is to determine what the agricultural and environmental consequenes are of change of soil P classes by means of a number of scenarios for P management as function of soil P status of arable land.