Botanical composition dynamics in fodder agrophytocenoses based on legume-cereal herbs

Various ecological and biological factors, including the composition of grass mixtures in crop rotation, affect the state of agrophytocenosis. The purpose of the research was to reveal the regularities of changes in the botanical composition of crops in forage agrophytocenoses depending on the duration of perennial legume-cereal grasses cultivation. The experiment was conducted according to B. A. Dospekhov’s “Methods of field research” on the experimental field of the Mari Research Institute of Agriculture, a branch of the FSBSI “Federal Agricultural Research Center of the North-East” in 2013–2018. In a two-factor field experiment, we studied the botanical composition dynamics in three six-field grain-grass crop rotations and goat-rump grass mixture (Factor A) with and without nitrogen fertilizing against the background of phosphorus-potassium fertilizers (Factor B). Soil of the experimental plots – sod-podzolic mid loamy. The meteorological conditions of the growing seasons were often unfavorable; therefore, the crops were strongly suppressed. The most drought-resistant species (sunflower, winter rye, alfalfa and barley with a mass fraction of 55 %, 97 %, 20 % and 96 %, respectively) had an advantage over weeds in grass mixtures by weight in the spring-summer period during the third rotation of the studied crop rotations. Plants of red clover and white mustard in the catch crop were strongly suppressed by drought. The clover-alfalfa-timothy grass mixture was replaced by forbs from 36 % in mass in the first year of use with a step of 23 % in subsequent years. After the 15-year usage, the second component in the grass mixture monocrop (Galega orientalis Lam. + Bromus inermis Leyss) completely dropped out. Non-sown grasses faster replaced the crop components of the herbage on the fields without nitrogen fertilizing. Thus, the crop rotation fields with the richly diverse crops composition and the nitrogen application were infested with fewer weeds (4.0–10.6 % by mass).