Formation of single-crop and mixed agrocoenoses of tall fescue under the conditions of Western Siberia

An increase in the cultivation of perennial of leguminous grasses and their combination with grasses is of crucial importance for the development of fodder production in Siberia. Long-term research has been carried out in the southern forest-steppe zone of the Omsk Region on meadow-chernozem soil. It has been established that grass mixtures with tall fescue and leguminous grasses are more productive than mixtures with grasses and single-crop seedings. Among the fallow grass mixtures, the highest yield (6.46 t/ha of dry matter) is represented by alfalfa + tall fescue, with an increase of 171% if compared to the control sample. The introduction of melilot and brome in the grass mixtures increases the yield, yet the substitution of leguminous grasses from the herbage is more active in mixtures with brome than in the ones without it. During the first free years the basic yield of grass mixtures is composed by leguminous grasses (65-87%), during the following years by grasses. Under the conditions of Siberia, mixtures with leguminous grasses and tall fescue actively use symbiotic nitrogen ( k fix = 0.62-0.71), the consumption of which depends on their composition and presence of leguminous grasses, while forming their yield. The highest consumption is observed in high-yielding grass mixtures with an increased content of leguminous grasses, tall fescue and alfalfa. The consumption of atmospheric nitrogen amounts to 140 kg/ha or 21.7 kg/t of dry mass, while k fix equals 0.7. Increasing the composition of grass mixture up to six species does not ensure an increase in productivity and nitrogen fixation if compared to two-crop mixtures.