Formation of yielding ability and cold resistance of three red clover and alfalfa cultivars

The goal of this study was to investigate cold tolerance, morphological characteristics and productivity of alfalfa and red clover varieties, that differed in hardiness.. The following varieties of red clover lite, Mars, Barfolia and of alfalfa Karlu, WL 324 and Medina were used. Seeding year yielding ability was connected foremost with genetic qualities. The highest partial DM yield (cv. Mars-4.49 and WL 324-3.22 t hr(-1)) was obtained in the medium winter-hardiness varieties. Differences (P < 0.001) in total DM yield between cv. lite and other red clovers are caused by there heading types. In harvest year yielding ability of red clover and alfalfa increased up to 2.8 times and differences between varieties enlarged. After favourable over-wintering, the highest partial DM yield (10.46-10.60 t ha(-1)) was obtained in cv. Mars and WL 324 sward. Heavy winter damage resulted in degradation and diminishing yielding ability of cv. Medina. The most sensitive to cold were Barfolia red clover and Medina alfalfa (LT50 = -9.8 and -8.5 degrees C, respectively in 2003 and -8.8 degrees C in alfalfa in 2004). In the harvest year, red clover was infected by root rot. That additional biotic factor caused a large dispersion of LT50 data. Growing ability of the surviving plants (after freezing) was rather different and connected with freezing temperature. However, morphological features are important as well. There was a correlation between the diameter of taproot and regrowth (P < 0.05 in red clover and P < 0.001 in alfalfa).