A series of processes that forms an integrated mechanism by which a cell or an organism detects the depletion of primary phosphorus source and then activates genes to scavenge the last traces of the primary phosphorus source and to transport and metabolize alternative phosphorus sources. The utilization process begins when the cell or organism detects phosphorus levels, includes the phosphorus-containing substances, and ends when phosphorus is incorporated into the cell or organism's metabolism. [ GOC:mlg GOC:mah ]