Technological features of cultivation of tilled crops, including potatoes, lead to a strong mineralization of humus, so the fertilizer system of crops includes the introduction of organic fertilizers. In order to achieve a deficit-free balance of humus in soils of Russia, 800 million tons of organic fertilizers, or 6–8 tons per hectare, per year, are required to be transferred to bedded manure. In Mari El, it is necessary to make at least 10 tons of semi-overgrown manure of cattle per hectare of sod-podzolic soils. The actual use of organic fertilizers does not exceed 10–12 %. The deficit of organic fertilizers can partly be solved by utilizing the chicken manure and using it in agriculture. The aim of the research is to establish the optimal preplant dose of granulated organic fertilizer on the basis of bird droppings while cultivating potatoes to increase the yield of tubers. Field experiments were laid on the territory of the Republic of Mari El. The soil cover of the experimental site is represented by a soddy-weakly podzolic low-humus medium loamy soil on the cover clay. The object of the study is the early root potato of the Crown variety. Granulated organic fertilizer (GOF), based on fermented bird droppings, was added manually when planted in each well ac-cording to the experimental design: 1) no fertilizer, 2) GOF 0,5 t/ha (10 g per well), 3) GOF 1,0 t/ha (20 g per well); 4) GOF 1,5 t/ha (30 g per well); 5) GOF 2,0 t/ha. The planting rate of potatoes is 50 thousand pieces / ha (5 pcs./m2). Repetition of the experiment is 3-fold. Placing options in the expe-rience is systematic. As a result of the research it was established that The use of granulated organic fertilizer increases the interphase periods of plant development, thereby extending the entire growing season of potatoes. The potato yield increases by 8,5–44,0 %, depending on the fertilizer dose. The most effective dose is 2,0 t/ha of GOF. It also increases the mass of tubers from one plant, while the average weight of the club and the mass of the fraction of large and medium potatoes increase significantly.