Abstract |
- California brome (Bromus carinatus Hook & Arn), is
considered an important weed infesting wheat and grass seed
fields in the Willamette Valley of Oregon. Field and
greenhouse experiments were conducted to study some
biological aspects to develop more efficient management
strategies.
A field experiment was conducted to determine the
effect of depth (0 to 30 cm) and duration (1 to 11 months)
of burial on germination, viability, and soil longevity of
seed. Seed depletion was directly related to depth and
duration of seed burial. Surface-sown seed germinated
gradually, reaching 81% after 7 months. Buried seed
germinated rapidly. Less than 3% of the initial population
remained ungerminated after 1 month at all depths. Seed
loss at depths of 10 to 30 cm was primarily due to in situ
germination, with little effect from induced or enforced
dormancy. Persistence of surface-sown seed was due to both
enforced and induced dormancy, with enforced dormancy being
the more important mechanism of seed persistence. Highest
degree of enforced dormancy (34%) was at 1 month, decreasing
after 3 months. Properly timed tillage can be important for
effective control since tillage increases germination,
reducing soil persistence.
Greenhouse experiments were conducted to determine if
imbibed seed vernalization promoted plant flowering. In the
first experiment, cold treatment (5 C) of 10, 15, and 20
days reduced the vegetative phase. Flowering was absent in
plants from seed receiving 5 days of cold and in
unvernalized plants after 96 days, when this experiment was
terminated. Plants from seeds vernalized for 20 days
flowered within 36 days after transfer from cold treatment
to the greenhouse. Number of culms per plant and shoot dry
weight were highest on unvernalized plants and plants
vernalized as imbibed seed for 5 days. Lengthening the
vernalization period from 10 to 20 days decreased the total
seed dry weight from 18.78 to 15.02 g. The ratio of total
seed dry weight to total shoot dry matter was highest for
plants vernalized as imbibed seed for 20 days. In the
second experiment, only plants from seed vernalized for 20
days flowered within 109 days after transfer to the
greenhouse, whereas plants from seed vernalized for 0, 5,
10, and 15 days did not flower. There was not a statistical
difference for number of culms per plant. Plant height was
consistent in all treatments, with the exception of plants
vernalized for 20 days, which were taller than plants of the
other treatments. Highest total shoot dry weight was
observed on plants from seed vernalized for 15 or 20 days.
The effect of differential soil placement of
cinmethylin (exo-l-methyl -4-(methylethyl)-2-[(2-
methylphenyl)methoxy]-7oxabicyclo[2.2.1] heptane), diclofop
((±)-2-[4-(2,4-dichlorophenoxy)phenoxy]-propanoic acid),
triallate (S-(2,3,3-trichloro-2-propenyl) bis(1-
methylethyl)carbamothioate), and trifluralin (2,6-dinitro-
N,N-diprony1-4(trifluoromethyl) benzenamine) on California
brome control was measured in the greenhouse, at a rate of
0.93, 1.8, 1.34, and 1.07 ppm, respectively. Cinmethylin
had the greatest affect on plant height and plant weight,
reducing both significantly. California brome plant height
and dry weight were not affected by herbicide placement.
Seedlings treated with diclofop with shoot plus root
exposure differed in plant height from those treated only in
the shoot or root zone. Seedlings with shoot exposure to
triallate did not differ in height or dry weight from plants
treated in the root or shoot plus root zone. Root exposure
to trifluralin reduced height and dry weight less than did
shoot or shoot plus root exposure.
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