@inproceedings{orgprints9905, title = {Phosphorus Management on `Extensive' Organic Farms with Infertile Soils }, author = {P. S. Cornish}, year = {2007}, keywords = {phosphorus, Australia, soil fertility, grain, grazing}, url = {http://orgprints.org/9905/}, abstract = {Two case-study farms with negative P balances maintained acceptable productivity without fertilisers, apparently by ?mining? ?available? P reserves in surface and subsoil. The question for these organic farms is ?how long before fertiliser is needed?? With six farms on lower-fertility, weakly acidic to alkaline soils and modest rainfall (380-580 mm/yr), low productivity was related to P deficiency despite positive P balances from using allowable fertilisers. Useful supplies of compost or manure were unavailable. Until effective allowable fertilisers or microbial inoculants have been developed, there is a case for using soluble forms of P fertiliser on soils where soil-solution P is low and soil P-sorption is high, so that additions of soluble P ?feed the soil, not the plant?.} }