Vol. 16—1962 - NorthEastern Weed Science Society

396
Third Year After Application (1961):
Observation of th~ P'l~t~' the' thiia ·yeal"-_,'af:t.e;rapplication!
(Table VIII) indicated only 10 to 30 per cent vegetation control
at the 10 pounds per acre rate; 10 to 60 percent control at the
16 pounds per acre rate; 20 to 90 per cent control at the 32 :
pounds per acre rate; and 10 to 80 per cent control at the 64
pounds per acre rate.
In general, most of the area which showed some degree of
below-plot injury to vegetation due to herbicidal transport the
first and second years Was recovered from the harmful effects by
the third year. (Table IX)
Most of· the areas which recovered from the effects of the
herbicides are now filled in with the species of grasses adjacent
to the area.
SUMMARY
In general there are a few main conclusions that can be
offered:
1) There was no long term significant difference due to
source of material under the conditions of this study; howeve!,?
the rate of active herbicide used was significant up to the third
year after application. It is doubtful that. ,any visible control
will be evident by the fourth year after application, even at the
highest rates. 1 ,
2) It would appear that the optimum vegetation control per
dollar of expenditure would be obtained at the 16 pounds per acre
active herbicide rate.
3) Type of soil (sandy soils used in tll.1s study) might pt'esumably
have some bearing upon the rate of vegetation recovery',
and upon the, extent of down-slope transport of the herbicide.
4) Prevention of concentrated water running over treated
areas would materially help to reduce down-slope transport of
herbicides. (There is no substitute of good construction and
sound run-off control.)
r .
5) Departmental experience with 6 to 8 year vegetation control
under guide rail fences after soil sterilization with herbicidesis
presumably the result of an adequate bitumen cover
applied immediately over the sterilized area? rather than to the
rate or kind of herbicidal soil sterilant Whlch was used. Thel
bitumen cover prevents re-entry of viable seed to the treated
soil, and materially helps to prevent down-slope transport of the
~homi~Q' i~~o'~_