Vol. 15—1961 - NorthEastern Weed Science Society

On the basis of the rhizomes obtained from one square foot of soil per
plot on each sampling date, the yields of rhizomes and fructose per unit
area, as well as the concentration of total fructose, were determined. This
paper deals only with the main effects of and interaction between chemical
and cultural treatments on the fructose content of the quackgrass rhizomes.
RESULTSANDDISCUSSION
The main effects of both cultural and chemical treatment's, as well as
their interaction, resulted in significant differences in the rhizome reserves
at the one per cent level throughout the experiment.
Main effects of cultural treatments:
The main effects of the cultural treatments on the carbohydrate content
of quackgrass rhizomes are given in Table I.
Both spring ploWing and fallow resulted in rapid decreases of about
50 per cent in fructose content. The single spring ploWing treatment continued
to hold the rhizomes near this low level of carbohydrates until late
autumn, when sufficient regrowth had taken place to again accumulate photosynthate
in the underground organs. It still showed a 15 per cent reduction
over the uncultivated plots, but this difference was no longer significant.
The data from the final sampling the following spring showed the fructose
content from the plowed rhizomea to be almost equal to the uncultivated
rhizomes.
On the other hand, the continuous fallow treatment continued to deplete
the rhizomes of their stored food, resulting in depletions of about 70 per
cent toward fall of 1959 and 74 per cent by May 10, 1960.
The data on fructose content over all sampling dates show that the
fluctuations in the per cent fructose of normal untreated rhizomes are small,
with the reserves remaining at a high level from early' summer to late autumn.
Winter respiration and early spring regrowth, however, caused a decrease in
the fructose content of about 50 per cent as seen from the data of May 10,
1960.
Main effects of chemical treatments:
The main effects of the herbicides on the carbohydrate content of quackgrass
rhizomes are given in Table II.
Atrazine was most striking in its effect on the underground reserves,
not only based on its rate and extent of reduction but also on its permanency.
It resulted in a very sharp and early decrease of 71 per cent in the fructose
content at the first sampling date. Its effect continued to increase slowly
until the carbohydrates had been depleted by 83 per cent by late autumn and
-..' 90 per cent by the following spring.
The effect of Simazine on the fructose content was somewhat slower,
resulting in a decrease of 54 per cent on June IS, but was almost equal to
321.