The true cost - or the opportunity cost - is the value of the extra output that could be produced if the nitrogen were used on another crop such as wheat.
The true cost - or the opportunity cost - is the value of the extra output that could be produced if the nitrogen were used on another crop such as wheat.
真正的成本，即机会成本，是如果把这些氮肥用于另一种作物，如小麦，所能得到的额外产量。