Phosphorus is finite natural resource and it is not viable, either economically or environmentally, to overfeed dairy cows with phosphorus. The surplus in the form of manure ends up on our arable land and leaks into rivers, lakes and oceans. A major part of the excess phosphorus as cows consume is excreted in faeces in the form of phosphates, which usually causes eutrophication more than other phosphorous compounds.
Maria Nordqvist has in her dissertation examined the extent of phosphorus overfeeding in dairy cows in organic and conventional production. Most of the cows in both organic and conventional herds were shown to have too much phosphorus in their feed. The degree of overfeeding was generally lower in organic herds.
Assuming that the 290 cows in the study are representative of all Swedish dairy cows, it would mean that Swedish cows each year are fed with approximately 1,800 tons unnecessary phosphorus. Both the total content of phosphorus and the soluble fraction of phosphates in faeces reflect the degree of phosphorus overfeeding.