The paper studies agricultural crops’ yield depending on quality of entering of mineral fertilizers. It is established that determining  average productivity, under square-law dependence of yield on a dose, there is not necessity to set  the law of fertilizers distribution across the field and will be sufficient to know  expected value  D and standard deviation sD. The paper considers approaches to economic-mathematical model of optimization of fertilizers’ doses at the differentiated entering. The produced result provides a new approach to the quality control in technological process of fertilizers application. Also, it allows formulating requirements to perspective technical means used for entering of mineral fertilizers.