Crop rotation effects on the seed bank and population dynamics of annual bluegrass (Poa annua)

Graduation date: 1999Field studies were conducted to evaluate the effect of crop rotation on annual bluegrass\ud plant population dynamics, seed rain, and seed bank in 1996 and 1997 at two sites.\ud Growth-chamber studies were conducted to determine the influence of the mother plant\ud environment on annual bluegrass germination. The change in population, seed rain, seed\ud in seed bank and germination behavior of annual bluegrass at Site 1 was different from\ud those at Site 2. The highest population of annual bluegrass was observed in the\ud meadowfoam-perennial ryegrass rotation and the lowest population was observed in the\ud continuous perennial ryegrass and meadowfoam-spring wheat rotations at Site 1 in 1997,\ud whereas continuous perennial ryegrass and winter wheat-perennial ryegrass rotations had\ud the highest populations at Site 2 in 1997. Differences in the number of annual bluegrass\ud seed in the seed bank occurred at both sites. The greatest reduction of annual bluegrass\ud seed in the seed bank was observed over time in the meadowfoam-spring wheat rotation\ud at both sites. At both sites, most of the seed was deposited on the surface to 0 to 2.5 cm\ud soil depth and the number of seed decreased with soil depth. The mother plant\ud environment and the date of seed maturity had an effect on annual bluegrass germination.\ud At the seed collection date of 5/8/97, the annual bluegrass seed collected from the canopy\ud of continuous perennial ryegrass and from the seedling perennial ryegrass following\ud meadowfoam had the highest germination at 15/25 C at Site 1. Seed collected from\ud continuous perennial ryegrass on 5/6/97 and 5/22/97 had the highest germination among\ud all test temperatures regimes at Site 2. Seed collected from seedling perennial ryegrass\ud following meadowfoam at the second collection date of 5/28/97 at Site 1 and 5/22/97 at\ud Site 2 had the lowest germination at all temperature regimes except 5 C constant\ud temperature. The 15/25 C was the best temperature regime for germination of annual\ud bluegrass collected from any mother plant environment on any seed collection date at\ud Site 1 and Site 2