%A P. S. Cornish
%T Phosphorus Management on ?Extensive' Organic Farms with Infertile Soils


%X 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?.
%D 2007
%K phosphorus, Australia, soil fertility, grain, grazing
%L orgprints9905