It should be stressed that the calculation of the MPP does not involve dividing the difference between the yield at a given level of fertilizer and the base yield when no fertilizer is applied by the total amount of fertilizer used.

• 应该强调的是，边际产量的计算并非是用一定的肥料用量水平下的产量与不用肥料的情况下的产量之差除以总的肥料用量。