<p></p><p>It is estimated that in the
United States, agronomic weeds are responsible for about 50% of crop yield
loss, costing nearly $27 billion each year. As interest in cover crops across
the Midwest increases, so does the need to understand when to terminate cover
crops for maximum weed control while still maintaining crop yield. Field
experiments were conducted in 2017 and 2018 in Indiana to evaluate the effect
of cover crop termination timings on weed control, and corn and soybean yield.
Cereal rye (<i>Secale cereale </i>L.) and
canola (<i>Brassica napus </i>L.) were
subjected to early- or late- termination utilizing glyphosate-, saflufenacil-
or glufosinate-based burndown herbicide programs. In corn, cereal rye and
canola reduced early season weed biomass by 58 to 67% compared to fallow (no
cover crop) plots. Cereal rye and canola reduced horseweed (<i>Erigeron canadensis </i>L.) and giant
ragweed (<i>Ambrosia trifida </i>L.)
emergence by 42 to 50% compared to fallow plots. Early- and late- terminated
cereal rye reduced corn yields by 55 to 67% (5,173 to 7,116 kg ha<sup>-1</sup>)
compared to canola or fallow plots. In soybean, cereal rye and canola reduced
early season weed biomass by 73 to 88% compared to fallow plots. Cereal rye and
canola reduced horseweed emergence in 2017 and 2018 by 16 to 67 % compared to
fallow plots. In 2017, both cover crop and termination timing influenced giant
ragweed emergence. Early- and late- terminated cover crop plots reduced giant
ragweed emergence by 50 to 76% compared to fallow plots. In 2018, cover crop
termination timing influenced soybean yield. Late-terminated plots reduced
yields by 48% compared to early-terminated plots. Results from this study
suggest that cereal rye and canola planted at these rates can be effective for
weed suppression prior to corn and soybeans, however, yield loss in both corn
and soybean is expected. </p><p>Reports
from Indiana in 2015 suggested that growers planting canola as a cover crop
were experiencing difficulties when terminating with glyphosate prior to corn
and soybean production. This suggests the utilization of inadequate herbicide
programs, or perhaps a seed contamination event containing glyphosate resistant
canola. Field experiments were conducted in 2016 and 2017 to determine the most
effective herbicide treatment for terminating glyphosate resistant canola in
Indiana, and to quantify how these herbicide programs influence corn yield.
Canola was planted in early September and herbicide treatments were applied in
the spring three weeks before corn planting. Visual ratings of control and
above-ground biomass reduction were collected 21 days after treatment (DAT).
The highest control of canola occurred following the application of paraquat +
saflufenacil + 2,4-D or metribuzin, resulting in 88 to 94% control. These
control ratings are supported by applications with paraquat + saflufenacil +
2,4-D or metribuzin resulting in 88 to 97% biomass reduction. Auxin herbicides
alone provided very poor control, less than 41% at both locations. In general,
saflufenacil-containing herbicide treatments provided the highest control of
canola compared to mesotrione or atrazine. Herbicide treatments had no effect
on corn grain yield.</p><br><p></p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/8026367 |
| Date | 14 May 2019 |
| Creators | Stephanie A DeSimini (6596888) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/Evaluation_of_Weed_Suppression_and_Termination_Timings_of_Cereal_Rye_i_Secale_cereale_i_L_and_Canola_i_Brassica_napus_i_L_as_Winter_Cover_Crops_in_Indiana/8026367 |
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