Aspects of phosphorous fertilisation in organic farming

Summary

Balanced fertilisation is essential for a considerate use of limited phosphorus (P) resources and for sustainability in organic farming. Plant available soil P levels will decrease and soil fertility will diminish when using P sources with limited P availability such as rock phosphates, bone and bone meals. An in situ digestion with a combination product of elemental S and rock phosphate enhanced significantly the solubility of non water-soluble P sources. In addition to the problem of insufficient solubility, mineral P sources can be contaminated with toxic heavy metals such as Cd 0.1–92.3 mg kg-1) and U (<LLD - 481 mg kg-1) from their source. Farmyard manure and slurry may contain up to 953/727 and 376/132 mg kg-1 Zn and Cu, respectively.