Vol. 15—1961 - NorthEastern Weed Science Society

326.
Another effect of Atrazine that should be pointed out is a characteristic
trend over all sampling dates under the superimposed cultural treatments.
Under continuous fallow, Atrazine resulted in a sharp and early decrease of
86 per cent on June 15. and showed little deviation from this value throughout
the season~ A decrea$e of 86 per cent was still maintained on November 10.
The single spring plowing follOWing treatment gave ,about the same early value,
showing 84 per cent depletion of fructose on June 15. 'Instead of remaining
constant or increasing in effect. the carbohydrate content increased slightly,
showing a reduction of only 78 per cent on November 10. When no cultivation
followed the application of Atrazine. samples collected on June 15 showed a
reduction of 85 per cent, indicating that essentially all of thiS early loss
of carbohydrates could be induced without any cultural treatment. However,
the fructose content of the uncultivated rhizomes continued to decrease
gradually throughout the season, resulting in abnost complete depletion of
98 per cent by November 10.
The effect of Simazine on the fructose content of uncultivated rhizomes
also tended to change from a 61 per cent to an 84 per cent reduction by
September 10, 1959. However, this effect was reduced sharply during the
winter and the following spring, shOWing only a 24 per cent decrease on May
10, 1960. Simazine plus spring plOWing gave an early sharp decrease of 87
per cent which dropped to 75 per cent by November 10, 1959 and 37 per cent
by May 10. 1960. Simazine plus fallow. on the other hand, tended to increase
the carbohydrate depletion and was always superior to the uncultivated
quackgrass treated with Simazine. showing a reduction of 92 per cent by
September 10.1959 which remained constant throughout the remainder of,the
experiment.
Applications of the other herbicides did not induce very large reductions
in the fructose content of rhizomes unless followed by tillage treatments.
Dalapon and Fenac with no cultivation showed early minor decreases of 24 and
23 per cent, respectively, but the carbohydrates gradually increased until
the rhizomes showed only 12 and 17 per cent lower fructose values on
November 10 than the untreated checks. By May 10, 1960 Fenac and Dalapon
under no cultivation showed fructose content values equal to or higher than
the quackgrass receiving no treatment. At no sampling date were these
differences significant .t the one per cent level.
Amitrol-T with plOWing or no cultivation gave significant reductions
over the untreated checks at all except the final sampling date. Without
cultivation. the reduction in fructose content amounted to 57 per cent by
August 5, 1959. However, the effect decreased toward the end of the season,
showing only a 28 per cent depletion on November 10, 1959 and May 10, 1960.
The fructose content values from Amitrol-T plus plOWing followed a similar
trend. decreasing to a depletion of 72 per cent by August 5, 1959. then
increasing again gradually to only a 30 per cent reduction by May 10. 1960.
The effectiveness of Dalapon or Fenac application on the carbohydrate
content of quackgrass rhizomes was considerably ,increased and prolonged when
accompanied by the single spring plowing. The·sprlng plOWing alone resulted
in an early rapid decline of 72 per cent in the fructose content. This
deficiency was replenished slowly to September 10. when a 50 per cent reduction