Flowering and seed production in meadow bromegrass

Meadow bromegrass (Bromus riparius Rehm.) is an important forage grass in western Canada. Economical seed production is critical to its use. Seed yield usually declines rapidly after two to three seed crops. Field and growth chamber experiments were conducted to determine the influence of (a) residue removal and N fertilization on tiller density and size, panicle density, silvertop incidence, seed yield and stand longevity, (b) filler size and stand age on panicle production, and (c) daylength and temperature during primary and secondary induction on panicle production. Removing residue after harvest and applying N (100 kg ha-1 ) increased yield from 200 to 450 kg ha-1 compared to not removing residue or adding N in the second seed crop. The difference between treated and untreated plots was only 30 to 90 kg ha-1 in the third seed crop. The increase was related to an increase in panicle production, however, the correlation between panicle number and seed yield was low. Silvertop incidence (% of panicles affected) increased as the stand aged, but removing residue after harvest reduced silvertop. In pot studies, the percentage of plants that produced panicles increased as tiller basal diameter increased from one mm to three mm, regardless of the age of the stand. However, fewer large tillers were observed in older stands. Large tillers from a four-yr-old stand produced fewer particles than large tillers from a two-yr-old stand indicating that tiller size alone is not responsible for the decline in panicle production. Panicle production increased as the temperature during primary induction decreased. However, daylength during primary induction had no effect on panicle production. Varying temperature or daylength during secondary induction had no effect on panicle production; panicles were produced in 85% of plants regardless of temperature, and 67 to 77% of the plants regardless of daylength. In conclusion, residue removal after harvest and N fertilization improve seed yield in young meadow bromegrass stands. However, these practices were not effective in prolonging seed yield beyond two to three seed crops. Drought, winter injury, competition amongst tillers and silvertop incidence all play a role in reducing seed production