Vol. 16—1962 - NorthEastern Weed Science Society

so11 per plot at each sampling date., the yield of l!",~omes and their fo04 reserve
content were determined. The yield of fructose p~l&l1it area was subsequently
calculated as the product of these two determinations.
291
Results
and Di,cussion
Main effects of cultural trea~~t,:
\
The main effects of cultural treatments on the' yield of quackgrass rhizomes
are given in Table I. Both the plowing and fallow treatments resulted in an
early decrease in the yield of.,J:l:a:f.'l:lIDes
about, 4PJpercent. The effect Df the
single spring ploWing tended to a~~ease throughoutlthe experiment as regrowth
of foliage occurred, although it continued to show lower yields than the uncultivated
quackgrass. The effect of continuous fallow, on the other hand, increased
and resulted in a decrease of a\)o,~$, 7S per cent infhizome yields by late autumn.
'"
J
The depletion of total carbohydrate yield due to cultural treatments was
especially severe as shown in Table II. The dataabow that the first plowing is
by far the most important s1ng1e)c~l~ural treatmenti'resulting in an earl, and
rapid decline of over 70 per cent' ~n the fructos."eld. Where no further
tillage was appl1l!d, however, tlHtfood reserves weregraduaUy replenished. By
late autumn the plowed plots were no longer significantly lower than the uncultivated
plots, and by the following spring the re~~don of total carbobY'lt:ate
was only 24 per cent. The fallowereatment continu.d a gradual depletion of
fructose yield to 94 per cent by late autumn, which 'persisted to the next spring.
Main effects of chemical treaem,~.ts:
The effect of herbicides onthe'dry weight yieids of rhizomes was always
significant throughout the experim£\~t, as seen in Tab,le III. AU of the :urbicides
with the exception of DalapOn caused an early and marked decrease in rhizome
yielda. Although only Atrazine.bowed a significant reduction of about SOper
cent by the first sampling date" tbe rhizome yield;teductions from Sfmazine,
Amitrol-T and Penac ranged betWeeri.~S and 39 per c~t. Throughout the remainder
of the experiment, Atrazine, Sfmazlne, and Amitrol continued showing,gradual
decreases in rhizome yields, resulting in eventual declines of 88, 76, and 68
per cent, respectively, at the f.l~,~ aampUng date'Jl Thes,e three herbicide,s
resulted in consistently lower survival of rhizomes than Penac or Dalapon. While
Penac showed only minor changes from the initial decrease of 35 per cent throughout
the remainder of the experi~nt, the effect of ntilapon was gradual and·
continuous throughout the growing ~aon resulting. in a 56 per cent lOBS of
rhizomes by late autumn. However, lta effect decre.sed during the winter and
early spring, showing a reduction 01 ,only 31 per cent by May 10,1960.
Since the herbicides generally, caused simultan.£lous reductions of both
rhizome yields and fructose content, the effects of chemical applications on the
total carbohydrate yields were considerably accentuated, as shown in Table IV.
Atrazine gave a very sharp and~arly,decrea.e in Ir~tOBe yield of 88 per ~ent
by the first sampling date one mOnt~:after application. Thia carbohydrate
depletion increaaed slowly throullloUtthe year to 97 per cent by autumn and 99
per cent by May 10, 1960. Simazine showed similar results although it reacted
slower, with an initial reduction of 72 per cent, and a 94 per cent reduction by
late summer. However, its effect decreased during the winter and early spring,