Productivity of binary legume-grass mixtures with birdsfoot trefoil (Lotus corniculatus L.) and white clover (Trifolium repens L.) on acidic sod-podzolic soils

Field studies investigating the productivity of binary pasture grass swards were conducted in 2023–2025 at the experimental field station of the Russian State Agrarian University – Moscow Timiryazev Agricultural Academy. The study aimed to determine the yield and persistence of birdsfoot trefoil (Lotus corniculatus L.) and white clover (Trifolium repens L.) in two-component mixtures with festulolium ( × Festulolium Aschers. et Graebn.), perennial ryegrass (Lolium perenne L.), and meadow fescue (Festuca pratensis Huds.) under three- and four-cutting regimes on poorly improved sod-podzolic soil. It was established that by the third year of life, white clover and birdsfoot trefoil became the dominant components of the agrophytocenoses, accounting for 46.6–61.0% of the yield. In single-species grass swards, the proportion of forbs increased to 28.7–35.0% by the third year. While nitrogen fertilization of grass swards at a dose of N120 reduced forb infestation to 10.7–17.8%, the lowest proportion of forbs (3.7–8.0%) was observed in legume-grass swards. In the second year, the dry matter yield of legume-grass swards ranged from 5.08 to 7.46 t/ha, increasing to 6.67–8.49 t/ha in the third year. On average over the three-year period, increasing the cutting frequency from three to four resulted in a 10.4% decrease in total forage yield. Birdsfoot trefoil-grass swards outperformed white clover-grass swards by 10.9%, nitrogen-fertilized single-species grass swards by 15.7%, and non-fertilized grass swards by 2.2 times.