Vol. 15—1961 - NorthEastern Weed Science Society

324.
Atrazine by September 10 when the carbohydrate depletion reached 79 per cent.
The effectiveness of Simazine~ however~ failed to persist~ and by May 10~
1960 the reduction in fructose content was only 43 per cent~ or less than
1/2 that of Atrazine. The difference between Atrazine and Simazine was never
s~gnificant until the final sampling period. However~ the fructose content
values resulting fram the action of both herbicides were significantly lower
at the one per cent level during the first four sampling dates than the
quackgrass receiving an application of Amitrol-T~ Fenac~ Dalapon or no
herbicide.
Treatment with Amitrol-T showed a small early decrease of 23 per cent
on June l5~ but it was significant only at the five per cent level. However~
its effect increased and resulted in carbohydrates ranging between 31 and 43
per cent lower than the untreated plots at the later sampling dates.
Applications of Fenac or Dalapon showed no significant effects on carbohydrate
content until fall. By September 10~ they resulted in decreases of
22 and 26 per cent~ respectively, which were significant only at the five
per cent level. Samples collected in late autumn 'showed only slightly
greater depletions which were highly significant compared to the quackgrass
receiving no herbicide. The effects of Fenac and Dalapon decreased slightly
during the winter and follOWing spring, shoWing significant differences only
at the five per cent level from the May 10~ 1960 data. Fenac and Dalapon
were never
significantly
two sampling
significantly different from each other.
lower fructose content
than Penac or
dates.
Interaction between cultural and chemical treatments:
Amitro1-T
Dalapon only
resulted
at the
in
first
Although the interaction between cultural and chemical treatments on
the fructose content of quackgrass rhizomes was highly significant at all
sampling periods and any trends throughout the season will be discussed~ the
data from only one period (November lO~ 1959) are presented in Table III.
An explanation for the significant interaction can be given by comparing
the effects of the various herbicides with each cultural treatment. The most
striking case is the treatment in which 'no cultivation was applied. The
greatest depletion of food reserves did not occur in the fallowed or plowed
quackgrass as might be expected. Atrazine actually enhanced the depletion
of carbohydrates when no disturbance of -the soil took place, though the
difference was not usually significant. With the exception of Atrazine, the
herbicides induced a relatively minor depletion throughout the season when
not followed by a cultural treatment. There was some indication toward the
end of the 1959 season that the S~azine application without cultivation was
equal or superior to the same application with cultivation. However~ by
May 10, 1960 the Simazine plots under no cultivation or single plOWing failed
to show significantly lower fructose content values than quackgrass receiving
no herbicide or cultivation. Until the May, 1960 sampling, the differences
between Atrazine and S~azine under the various cultural treatments were
never significant at the one per cent level, although they were always
significantly lower than the uncultivated check.