The article shows for the first time the results of studies on the aftereffect of 4 years of a single use of dairy industry waste - cake as a fertilizer for crops in the crop rotation link: potatoes - spring wheat - potatoes - barley on productivity and product quality. In the spring of 2017, the experimental plot after harvesting the remains of perennial grasses was mechanically processed with a motor cultivator and divided into plots of 10 m2 with the following experimental options: 1. Control (without fertilizers); 2. Complex mineral fertilizer - azophoska with the content of plant nutrients N - 16%, P2O5 - 16%, K2O - 16% at the rate of 100 kg/ha; 3. Cake 3 kg/m2 (30 t/ha); 4. Cake 6 kg/m2 (60 t/ha); 5. Cake 9 kg a.i./m2 (90 t/ha). Variants of experiments were studied in six repetitions. The cake substance gradually mineralizes in the soil and supplies crops with nutrients throughout the growing season. The aftereffect of the cake was studied from 2018 to 2020, and for all the years of research, the maximum yield was observed in the variants with the introduction of cake. So, if in 2020 in the control variant the yield of barley was 2.13 t/ha, then in the variant with azofoska - 2.21 t/ha; in the option of 30 t/ha of cake - 2.41 t/ha; in the option of 60 t/ha of cake - 2.95 t/ha; in the variant 90 t/ha of cake - 3.10 t/ha (HCP05 = 0.22). The agrochemical properties of the soil in the variants with cake application improved significantly: the humus content in the control variant - 3.03%, in the variant with azofoska - 3.16%, in the variant 30 t/ha of cake - 3.22%, in the variant 60 t/ha ha of cake - 3.65%, in the option of 60 t/ha of cake - 3.60%. The content of plant-available forms of phosphorus and potassium in the soil also increased. The pH values of the exchangeable acidity increased to neutral values (6.59).