Although there was a 300% increase
in no-tillage acreage in the midwestern U.S. during the 1990’s,
vegetable growers have been reluctant to use no-tillage practices.
Weeds are a major problem in no-tillage vegetable production systems
and there are few herbicides available to control weeds in most vegetable
crops, as the use and number of herbicides available are dependent
on the specific vegetable grown. The adoption of no-tillage by commercial
vegetable growers has been limited and improved weed management practices
need to be developed before no-tillage systems in vegetable production
will be readily adopted.
Approximately 2500 acres of zucchini and yellow squash are grown in
Illinois. Growers apply preemergence herbicides regardless of whether
conventional tillage or no-tillage is used, and squash is transplanted
into herbicide-treated soil. Squash growers complain that harvesters
cannot locate fruit as easily on squash plants that are shaded by
weeds compared with those growing in a weed-free field, and this contributes
to reduced harvest efficiency and yield loss. Research has indicated
that when weeds are sufficiently controlled, squash grown in no-tillage
yield similarly to those grown in conventional tillage.
No-tillage, in conjunction with the use of winter cover crops, can
become an important part of vegetable production by reducing soil
erosion and aiding in weed control. Winter rye can suppress weed densities
in no-tillage production systems, however, small grain cover crops
(e.g. winter rye) must be killed to minimize competition with the
vegetable crop. Differences between winter rye cultivars have been
found for allelochemical levels, which could influence weed suppression.
‘Wheeler’ winter rye had higher levels of the allelochemical,
DIBOA [2,4- dihydroxy- 1,4- (2H) -benzoxazine- 3- one], compared with
several other cultivars. The objective of this study was to evaluate
the effectiveness of different winter rye cultivars (‘Wheeler’
as well as two others recommended for use in southern Illinois) along
with various pretransplant herbicide treatments for weed control in
no-tillage zucchini squash production.
‘Elbon’ or ‘Maton’ produced higher biomass,
greater soil coverage, and higher weed control compared with ‘Wheeler’.
Although winter rye alone did not provide sufficient weed control
(generally < 70%), it provided substantially greater redroot pigweed
(Amaranthus retroflexus) and smooth crabgrass (Digitaria ischaemum)
control (regardless of cultivar used) compared with no winter rye
at both 28 and 56 days after transplanting (DAT). No effect (P >0.05)
of winter rye cultivar on early or total squash yield was detected.
Although applying clomazone + ethalfluralin to winter rye residues
improved redroot pigweed control compared with no herbicide , the
level of control was generally not adequate (<85% control) by 56
DAT. Treatments that included halosulfuron provided greater control
of redroot pigweed than clomazone + ethalfluralin, and redroot pigweed
control from halosulfuron treatments was similar to the weed-free
control.
However, regardless of year or cover crop,any treatment with halosulfuron
caused unacceptable injury to zucchini squash plants which lead to
reduced squash yield (primarily early yields). Insignificant amounts
of squash injury (<10% due to stunting) resulted from clomazone
+ ethalfluralin in no-tillage plots during either year. Treatments
with clomazone + ethalfluralin had early and total yields that were
similar to those of the weed-free control, although this herbicide
combination provided less weed control compared with the weed-free
control.
