Regrowth of Bromegrass Species, a Bromegrass Interspecific Hybrid, and Meadow Foxtail in a Short-Season Environment

Regrovrth in pastures is critical to economic production in short-season areas. This study compared regrowth characteristics among three Bromus genotypes and meadow foxtail (Alopecurus pratensis L.) during late summer and fall. Growth analyses were conducted and yield components were determined in ‘Carlton’ smooth bromegrass (B. inermis Leyss.), ‘Regar’ meadow bromegrass (B. riparius Rhem.), an experimental strain (S9044) derived from F₂ plants of a smooth ✕ meadow bromegrass cross, and common meadow foxtail. Seven weeks of plant regrowth after severe defoliation were characterized during 1985 and 1986 at Lacombe, AB, Canada (52° 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 bromegrass consistently yielded less dry matter (DM) and had lower crop growth rates (CGR) than the other genotypes. Smooth bromegrass seemed limited most by a slowly developing leaf area index (LAI) as a result of a low and slowly developing tiller density. S9044 was improved over smooth 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 rate than in smooth bromegrass. Meadow bromegrass had CGR and DM yield similar to S9044, but the average LAI for meadow bromegrass was only 71% of that for S9044. Meadow bromegrass compensated for a small LAI with a specific leaf weight that was 1.4-fold higher than S9044. When soil water was adequate, meadow foxtail produced regrowth equal to S9044 and meadow bromegrass through rapid development of leaf area of moderate specific leaf weight and a relatively large tiller size, given a high tiller density. As exhibited by meadow bromegrass, high specific leaf weight combined with rapid tiller development are traits associated with regrowth yield that may be worth exploiting in developing germplasm for short-season areas where small LAI may be the norm. Submitted as Scientific Paper no. 768, Agric. Canada, Res. Branch, Lacombe Res. Stn., Bag Service 5000, Lacombe, AB TOC ISO, Canada.