The project focussed on phosphorus (P) and potassium (K) status of northern cropping soils.

Stores of P and K have been depleted by crop removal and limited fertiliser application, with depletion most significant in the subsoil. Soil testing strategies are confounded by slowly available mineral reserves with uncertain availability. We have assessed the utility of new soil tests to measure these reserves, quantified their availability to plants and undertaken a regional sampling strategy to identify areas of greatest P and K deficit. Fertiliser application strategies for P and K have been tested and the interactions between these and other nutrients determined in a large field program.