SAARELA, I., A. JÄRVI, and H. HAKKOLA. 2004. “Phosphorus Status of Diverse Soils in Finland As Influenced by Long-Term P Fertilisation 2.Changes of Soil Test Values in Relation to P Balance With References to Incorporation Depth of Residual and Freshly Applied P”. Agricultural and Food Science 13 (3):276-94. https://doi.org/10.2137/1239099042643099.