Does Herbicide Tolerance Mean Higher Yielding Hybrids?
When evaluating corn hybrids, how concerned should growers be that herbicide tolerant hybrids were actually treated with the appropriate herbicide?
When trying to
assess the impact that a herbicide program has on corn yield, there are a number
of factors that a producer needs to keep in mind. Here is our list in order
of importance:
1) On Target: a herbicide program needs to be well suited for the weed spectrum
in the field.
2) On Time: herbicides need to be applied in a timely fashion so that weeds
are brought under control early; by the time the corn plant has 3 leaves, your
program better have weeds under control or yield may start to evaporate.
3) Crop Safety: herbicides should put minimal stress on the crop.
4) Smooth Harvest: herbicide programs provide control such that harvesting problems
and/or weed seed returns are kept to a minimum.
In reviewing this list, it is apparent that herbicide tolerant hybrids and their
associated weed control programs can have an influence on the way we view each
of these four factors. When working with broad-spectrum, non-selective herbicides
such as Liberty or Roundup, being on target has become less of an issue. In
conventional herbicide programs, growers need to be more aware of the weed spectrum
they have in their fields and be sure to select programs that meet those specific
needs.
Weed researchers and the crop production industry have done a good job of defining
the need for weed control to be ‘on time’. For the most part this
has meant understanding the period of time within the crop’s life cycle
where it is absolutely critical that weeds are not allowed to compete with the
crop. In most cases this has translated into an increased concern over herbicide
applications that are made later than the ideal time. With conventional chemistry,
if you applied the product late you were often left with enough weed escapes
to remind you right up until harvest that your untimely weed control probably
cost you significant yield. Herbicide tolerant systems have changed that perspective
somewhat. You can still apply the herbicide too late, your corn will still suffer
from too much early weed competition, and yields will still be reduced. However,
now when you come back into the field to harvest, it is absolutely weed-free
because that 8-leaf stage application of glyphosate cleaned up everything! The
need for on-time weed control with herbicide tolerant hybrids is still very
important even if it is not as obvious.
Crop safety has also been looked at differently as the result of hybrids that
have been genetically engineered to be tolerant of specific herbicides. Here
is the key question raised on this issue: Do conventional herbicides cause more
crop injury and yield loss than if that hybrid was managed under the applicable
herbicide tolerant program? The answer here is a resounding – Maybe! Are
you a producer who is stretching time and equipment as thin as possible and
therefore spraying a lot of post-emerge herbicides in less than ideal conditions
or at less than the ideal crop stage? If so, then yield loss from crop injury
is a risk to deal with. Planting some of your crop with herbicide tolerant hybrids
may be a good strategy to deal with part of this risk. If however, you successfully
lay down a balanced attack of soil-applied herbicides and on-time post-emerge
products, the possibility of boosting yields just because you switch to a herbicide
tolerant program is minimal.
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Herbicide
tolerant hybrids or not, weed control
timing is critical! |