Productive longevity of different alfalfa varieties in the Central non-Chernozem region

摘要

Productive longevity of different alfalfa varieties depends on soil fertility, weather conditions, intensity of use and disease incidence. The pasture-type alfalfa (Medicago varia Martyn.) variety Pastbischnaya 88 was tested for long-term persistence onwell cultivated soils. In the 5th and 6th years of use 36-72 plants were left per 1 m2 and dry matter yields reached 5-7 Mg ha~(-1). Thinning of the swards was recorded both after unfavourable winter conditions and due to the diseases in the summer period. By the 15-17* year of use the productivity of alfalfa-based swards declined to 2.8-3.12 Mg ha~(-1). Being well provided withP and K on the sod-podzolic soil, alfalfa persisted in the mixtures with smooth brome even in its 18th year of use. Presence of1-7 alfalfa plants per 1 m2 provided significantly higher yields than pure grass stands. Smooth brome is a good companion grass in alfalfa-grass mixtures for long-term twice-a-season use. This species considerably resisted dandelion invasions and did not suppress alfalfa. The key condition of smooth brome persistence in mixtures with other gramineous grasses is annual application of N_(90) Without mineral nitrogen fertilization the swards were invaded by wild grasses and dandelion, and the share of smooth brome decreased to 10-18%. On moderately rich soils serious thinning of alfalfa-timothy swards was already recorded in the 4th year after sowing. Their productivity declined to a level of 1.58-2.92 Mg ha~(-1). Productivity of alfalfa-grass mixtures exceeded that of the single-species timothy crop by 1.8-2.0 times.