Characteristics of growth and development of perennial grasses on the basis of meadow tetraploid clover

Perennial grasses are less dependent on weather and soil conditions than other crops due to their plasticity, low demand for growing conditions, and a large variety of species. In 2013-2017 in the conditions of the Udmurt Republic the biological properties of meadow tetraploid clover (Trifolium pratense L.), alfalfa changeable (Medicago x varia Martyn), birds-foot trefoil (Lotus corniculatus L.), eastern galega (Galéga orientális Lam.) and timothy grass (Phleum pratense L.) in double and triple agrocenoses were studied according to the age of the grass stand and the term of mowing. Plant density of perennial grasses in agrocenoses depended on the biological characteristics of the species, the age of grass stand and the term of mowing. In the first year of use of agrophytocenoses the density of stalk stand was at the level of 374-542 pcs /m2, in the second year of use it was a little higher (348-688 pcs /m2), in the third year of use – 240-594 pcs /m2. High density of meadow tetraploid clover in the grass stand was noted in the second year of use – 266-520 pcs/m2. The number of timothy grass stems (122-194 pcs/m2) in the grass mixture was high even in the first year of grass stand use, in the following years there was a further increase of this indicator to 196-412 pcs/m2. By the third year of use there was an increase in the number of stems of alfalfa changeable to 86-148 pcs/m2 and birds-foot trefoil – up to 108-200 pcs/m2. The plant density of the eastern galega in agrocenoses was low. The agrometeorological conditions of the year and the term of mowing affected the height and leafiness of perennial grass plants in agrocenoses. The leafiness of meadow tetraploid clover reached 64%, of the eastern galega – 74%. Timothy grass plants were less leafy – 23-38%. The height  of meadow clover plants was at the level of 51 cm, of timothy grass – 75-78 cm. Birds-foot trefoil was the shortest component of grass mixtures. High yield of dry mass of single-species sowing of meadow tetraploid clover was obtained in the first two years of use – 7.8 and 6.5 t/ha, respectively. By the third year of use, the productivity of clover decreased to 2.9 t/ha. The highest yields for the years of research were formed by the following agrocenoses: clover + alfalfa, clover + timothy, and clover + alfalfa + timothy – 5.9-6.3 t/ha.