The aim of this diploma thesis was to find out the causes of low returns on chosen cereals (oat, wheat, rye, and spelled) in ecological agriculture based on evaluating information on growing procedures obtained via the method of questionnaires. Gradually, 21 ecologically farming companies controlled by the Abcert AB a Biokont CZ, s.r.o. organizations were chosen. Based on the analysis of growing procedures, the most frequent mistakes made by farmers were identified. Companies with lower returns apply mainly an inappropriate structure of crops grown, a high representation of cereals, and they do not respect crop rotation principles. Especially in favourble conditions, some farms are run without livestock production. Leguminosae representation is low in most companies, intercrops are used very seldom. In case of straw plow, the C:N ratio is not maintained using manure. Mineral manure is not used at all, liming very seldom. Vegetation is usually not fertilized during vegetation period. Cereal weed regulation is carried out, but not sufficiently. Using farm seed is quite frequent, which increases the growth of weed. Comparing returns on cereal among better and worse companies, it is obvious that respecting given principles may increase return on seed in 1.0 to 1.9 t/ha.