REGROWTH OF BROMEGRASS SPECIES, A BROMEGRASS INTERSPECIFIC HYBRID, AND MEADOW FOXTAIL IN A SHORT-SEASON ENVIRONMENT

Regrowth in pastures is critical to economic production in short-seaso n areas. This study compared regrowth characteristics among three Brom us genotypes and meadow foxtail (Alopecurus pratensis L,) during late summer and fall, Growth analyses were conducted and yield components w ere determined in 'Carlton' smooth bromegrass (B. inermis Leyss.), 'Re gar' meadow bromegrass (B. riparius Rhem.), an experimental strain (S9 044) derived from F-2 plants of a smooth x meadow bromegrass cross, an d common meadow foxtail. Seven weeks of plant regrowth after severe de foliation were characterized during 1985 and 1986 at Lacombe, AB, Cana da (52 degrees 28' N lat), The variation among the three grass species and the interspecific hybrid that was most critical to regrowth yield occurred during the first 21 to 28 d after defoliation, Smooth bromeg rass consistently yielded less dry matter (DM) and had lower crop grow th rates (CGR) than the other genotypes. Smooth bromegrass seemed limi ted most by a slowly developing leaf area index (LAI) as a result of a low and slowly developing tiller density, S9044 was improved over smo oth bromegrass for regrowth yield and traits related to rapid regrowth , S9044 approached equilibrium tiller density quickly and had a large leaf area per tiller, which resulted in a higher leaf area expansion r ate than in smooth bromegrass. Meadow bromegrass had CGR and DM yield similar to S9044, but the average LAI for meadow bromegrass was only 7 1% of that for S9044. Meadow bromegrass compensated for a small LAI wi th a specific leaf weight that was 1.4-fold higher than S9044, When so il mater was adequate, meadow foxtail produced regrowth equal to S9044 and meadow bromegrass through rapid development of leaf area of moder ate specific leaf weight and a relatively large tiller size, given a h igh tiller density. As exhibited by meadow bromegrass, high specific l eaf weight combined with rapid tiller development are traits associate d with regrowth yield that may be worth exploiting in developing germp lasm for short-season areas where small LAI may be the norm.