The paper presents the results of determining the content of coumarin and its derivatives in the melilot using nuclear magnetic resonance spectroscopy, including the study of the effect of fertilizers on the quantitative content of coumarin and its derivatives in the composition of the melilot treated by phases using the method of 1H and 13C nuclear magnetic resonance spectroscopy. Based on the results of the nuclear magnetic resonance spectroscopy, the possibility of qualitative and quantitative determination of the content of coumarin and its derivatives isolated from extracts of fertilized melilot was evaluated. The effect of eight preparations on the plant and its concentration in solution on the content of coumarin substances in the Altynbas yellow melilot variety was studied. It was shown that the preparations have a slight effect on the coumarin content in the melilot and, accordingly, on the quality of feed based on it. In the control variant (variant 9), the coumarin proton content was 9.85%, and the maximum coumarin proton content was observed in the variant where BioEnergy was used as fertilizer and amounted to 22.44%.