First, you need to determine what the key nutrient is in the mineral mix. For example, if your main interest is supplying phosphorus, then the easiest calculation is to determine the cost per unit of phosphorus (typically per pound of phosphorus). This is calculated by taking the cost of the mineral mix per ton times the phosphorus content, giving the pounds of phosphorus that a mineral mix supplies. Then divide the cost per ton by the pounds of phosphorus in the mineral mix. Table 1 gives an illustration of how three minerals might be compared.
Table 1. Varying mineral mix prices with the cost/lb of phosphorus.
Mineral mix Cost/ton Phos. Content Cost/lb Phos.
A $400 12% $1.67
B $300 8% $1.87
C $250 8% $1.56
