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| Herbicides that are typically used for weed control in food plots cannot be used in certified organic production systems. |
Interesting
questions arise from telephone calls and e-mails. One series of weed-control
questions came from a customer who had hunting rights on a certified organic
dairy. Herbicides that are typically used for weed control in food plots cannot
be used in certified organic production systems, and the customer needed guidance
on how to manage weeds without compromising the dairy's organic certification. This
is a unique and challenging question that closely parallels my area of research
in my full-time job.
This question is equally relevant when multi-species
forage blends are planted for food plots and the species have varying tolerance
to herbicides. In both examples, the panic-fueled question is the same: “How
are weeds managed without herbicides?”
Forage crop production practices that suppress
weeds and encourage crop growth are the foundation for any weed management system,
in any crop. In situations where herbicides are not an option, cultural weed control
transforms from a foundational practice to the primary means of weed control. A
cultural weed control practice commonly recommended is the use of stale
seedbeds, also called false seedbeds. A stale seedbed is a seedbed prepared
several weeks or months prior to seeding the forage. Stale seedbed weed control
works by stimulating the germination of non-dormant weed seed and
simultaneously controlling newly emerged weed seedlings before planting food
plots.
There are a finite number of weed seeds in the soil and those that
potentially infest crops are present in the upper two to three inches of the
soil. Granted, the number of weed seeds may be in the millions per acre and
there is no practical way to predict that number. Furthermore, weed seed
germination varies according to weed species, soil type, geographical location,
and current environmental conditions. As a general rule, repeated shallow
tillage of stale seedbeds will stimulate germination of a large portion of the
non-dormant weed seed in the upper two to three inches of the soil profile. Repeating
shallow tillage at two-week intervals will simultaneously control the emerged weed
seedlings and stimulate germination of a fresh batch of weed seed. Continuing
this cycle of intermittent shallow tillage of stale seedbeds during fallow
periods will reduce baseline weed densities before the forage blend is seeded.
This does not deplete all viable weed seeds in the soil since some are dormant
and located well below the depth of tillage. However, research has shown this
system of cultural weed control is a proven means to substantially lower the
baseline weed density.
Compared to the U. S., Europe has traditionally relied
more on cultural and mechanical weed control strategies than herbicides, and
much of the useful supporting research is European. Studies conducted in
Denmark showed that stale seedbed weed control reduced weed growth up to 84
percent compared to plantings that did not use stale seedbed weed control. It
should be obvious that stale seedbed weed control is not a stand-alone weed
control strategy. It is simply one tool in the weed control tool box that can
be used in virtually every food plot system — a crescent wrench of sorts.
There
are three critical characteristics of a successful stale seedbed weed control
program. First, start the process early, several weeks or months prior to
seeding the forage blend if possible. Second, shallow-till the seedbeds at
two-week intervals. Third, use an implement that thoroughly tills the top two
to three inches of the soil. The best implement is a PTO-tiller since it is a
shallow tillage implement that pulverizes the soil. However, two perpendicular
passes with a disk harrow is an acceptable alternative. Regardless of the
implement, repeat the process three or four times for maximum benefit.
A
variation on stale seedbed weed control is the use of a non-selective,
broad-spectrum herbicide such as glyphosate (Roundup and generics) to control
emerged weeds on the seedbed before planting forages. Glyphosate has basically
no soil-residual properties and will not affect forages when applied before
planting. The key to using glyphosate as a stale seedbed weed control tool is timing;
weeds need to be emerged and actively growing for optimum performance. In
addition, time is needed to allow glyphosate to translocate in the vascular
system of weeds to the roots for optimum performance; meaning that treated
weeds need to remain undisturbed for several days after treatment.
Glyphosate
for stale seedbed weed control is particularly useful where perennial weeds
(briars, bramble, Johnson grass, common Bermuda grass, quack grass, etc.)
infest the site. Seedbed tillage alone will not control perennial weeds
outright, but glyphosate can provide valuable control of perennial weeds. In
fact, the tandem system of stale seedbed tillage coupled with an application of
glyphosate is probably the best stale seedbed weed control system, with the
combination being synergistic to each component alone.
For the tangible
benefits of stale seedbed weed control, there are disadvantages that need to be
considered. Frequent and intense stale seedbed tillage in not a good soil
stewardship practice, particularly in areas where soil erosion is problematic.
When done correctly, stale seedbed tillage eliminates all vegetation (i.e.
weeds) short term and creates a condition for erosion. Secondly, stale seedbed tillage
alters soil physical structure and can cause soil compaction. The degree to
which this occurs varies according to tillage implement, frequency of tillage,
and soil type. These are unfortunate outcomes that cannot be overlooked.
In
professional agricultural circles, there are many advocates of no-tillage crop
production with a stated advantage of no-tillage being fewer weeds due to
non-disturbed soil and weed suppression by cover or smother crops. While
research data does not always support their position, they are repulsed by the
idea of repeated stale seedbed tillage. I will not use this article as a means
of refuting their contention. In fact, no-tillage advocates have legitimate
points.
So, we have a paradox; promote soil health and practice good soil stewardship
by reducing or eliminating seedbed tillage; or intensively till seedbeds before
planting forages to deplete weed seed. That is a tough choice. I have been beaten
senseless by my organic crop production customers with the same argument. My
response back to organic growers (and in our case customers who plant
multispecies forage blends in food plots): How will weeds be controlled if
tillage is removed? Pick your poison. When considered long-term, it makes sense
to me as someone who studies weeds and personally struggles with weed control
in food plots, that a system built around stale seedbed weed control does not
have to be a permanent production practice. It can be gradually transformed
into a minimum tillage system once baseline weed populations are reduced to a manageable
level.
This article began with a discussion about food plot management on a
certified organic dairy and the need to manage food plots without compromising
the owner’s organic certification. This real-world example parallels the
constraints of weed control in food plots planted to a blend of several forage
species. In both cases, the tools for successful weed control are limited and
selective herbicides are not always an option. Study the entire system of
forage crop production practices and focus on the weed control benefits that
they provide. Stale seedbed weed control is a useful and versatile weed control
strategy; a crescent wrench of sorts. While stale seedbed weed control is not
stand-alone and certainly has a down-side, consider it to be the ‘go-to’ method
to reduce weed populations and stay ahead of weeds in food plots.
