Potential of the Productive Longevity of Legume–Bluegrass Mixture in the South of Western Siberia

Perennial legume–bluegrass herbaceous stands stabilize forage production for highly productive livestock farming and make a significant contribution to the nitrogen balance of agroecosystems in Western Siberia. The purpose of the research was to study the effect of mineral nutrition conditions on the growth, development, and dry matter yield of a mixture of goat’s rue and brome grass in the forest-steppe of Western Siberia. The research was carried out in 2000–2021 in a stationary field experiment on meadow-chernozem medium-deep medium-humus heavy loamy soil in the Omsk region. The experiment was carried out in a reserve field (8-field crop rotation: eastern galega, eastern galega + brome, spring barley, field pea, sweet sorghum, and alfalfa + brome, forage beans, and millet + rapeseed) according to the scheme providing for the study of the following variants: potassium fertilizer (factor A) (K0 and K60); nitrogen fertilizer (factor B) (N0, N30, and N60); soil supply with mobile phosphorus (factor C) is medium (according to F.V. Chirikov, 70–80 mg/kg, background 0), increased (120, background I, and 140 mg/kg, background II), and high (150–160 mg/kg, background III). The most balanced ratio of legume and bluegrass components was observed on the backgrounds with increased and high contents of mobile phosphorus in the soil. The competitive ability of goat’s rue increases without the addition of nitrogen fertilizers against these backgrounds, which is ecologically and economically effective. Against the background of irrigation, the yield of the grass mixture reaches 8–9 t/ha of dry mass in variants with a sufficient level of phosphorus (increased and high content) vs. 6.35 t/ha without fertilizers. In subsequent years, in the absence of irrigation, the picture changed towards a general decrease in yield to 5–6 t/ha of dry mass in fertilized variants vs. 3.60–4.81 t/ha in the variant without fertilizers. In the second decade, the average statistically significant value of yield growth is 0.49 t/ha in variants without nitrogen fertilizers in 2011–2015 and 0.99 t/ha in 2016–2021 as a result of an increase in the share of goat’s rue in the botanical composition.