Vol. 15—1961 - NorthEastern Weed Science Society

304.
b) Seed tolerance trials
Plots 6r x 20' (120 sq. ft.) were laid out in a newly fitted
area. Dry and liquid materials were applied as in the preemergence
trials. One foot wide rows of different grasses
were seeded the following day and at intervals of one, two
and four weeks. Half of each plot was raked lightly before
and after seeding. No mulch was used, but irrigation was
available and was used as needed to keep the soil surface damp.
"
c) Seedling tolerance trials
Strips ,- x lOOt (500 sq. ft.) were seeded to pure stands of
Seaside berrtgrass , Kentucky bluegrass, Chewings fescue, perennial
ryegrass and smooth crabgrasses and \1Ihite Dutch c'lover , At two
time intervals after sprouting, l8-inch bands of chemical were
applied across these strips with a 6ftinch check strip left
between each treated band. Dry' formulations were weighFd out
in advance and applied by hand. Sprayed materials were mixed
in the equivalent of 180 gpaof water and applied with a single
nozzle backpack sp::ayer. No mulch was used, but irrigation was
available and was used as needed to keep the soil surface damp.
Observations
a) Pre-emergence crabgrass trials
On June 1" August 15 and Septeniber 30, visual estimates were
made of the proportion of each plot infested with crabgrass.
The nine check plots were averaged and taken as the standard.
The three replications of each treatment were averaged and
compared to the standard to determine the percent crabgrass .
control produced by each treatment. These resu1ts are reported
in Table I.
b) Seed tolerance trials
On July 8 and August 25, visual estimates were made of the stand
of grasses in each plot. The stand of grasses in the check plots
was rated as "10" and stands in treated plots were related to
this. A rating of flO" indicates complete inhibition of seed
growth. Resu1ts are reported in Table II.
c) Seedling tolerance trials
On June 6 and July 8" visual estimates were made of the injury
and/or reduced stand of each species of seedling grass. The
stand of grasses in the check rows was rated as "10" and stands
in treated rows were related to this. A rating of flO" indicates
complete post-emergence kill of seedling grasses. A rating of
"7" or less indicates objectionable injury. Results are reported
in Table III ..