|
 Before deciding whether it
is worth it to plant a cover crop, it is important to find out what
is beneficial. Producers should examine what cover crops actually do
for the soil and what cover crops will work best. Some of what is
being promoted is not actually that effective in central Illinois,
so that is one aspect that should be considered.
The costs for planting cover crops are another factor to consider.
Earlier this year, the Environmental Quality Incentives Program (EQIP)
offered financial assistance to those wanting to implement
conservation practices to address concerns such as soil erosion.
A look at the extensive research on cover crops can help determine
whether or not cover crops can be beneficial for you.
Selecting the right seeding program
With cover crops, choosing the right seeding program is important.
An article by the Rodale Institute says, “Farmers sometimes choose
to plant different cover crops based on their root structures.” To
“help prevent runoff and soil erosion,” use cover crops such as
rapeseed that have wider roots.
Other types of root structures provide different benefits. For
aiding in aeration, the Rodale Institute says it is better to choose
cover crops like oats and radishes with “narrower, longer root
structures.” Soil compaction can be bolstered by cover crops like
wheat and cereal rye, which have “denser root structures.” Finally,
“covers with lighter roots like barley and winter pea support water
filtration.”
In “Consider Cover Crops this Fall,” Nick Frillman says, “[utilize]
common cover crop seed for fall and winter including oats, field
pea, hairy vetch, various kinds of clover, winter kale, winter rye,
and more. If you are worried as you have never done this before or
new to cover cropping; a field pea and oats mix is a sturdy,
reliable pair of plants to start with.”
A U of I Extension article “Let plants do the work, it's time to
plant fall cover crops” says the combination of oats and field peas
“offer high rates of success regardless of a farm’s experience with
cover crops. Both oats and field pea are quick to germinate in most
soil conditions and grow quickly to establish a living mat of
organic matter that suppresses weeds.”
In cornfields, winter cereal rye can be a good cover crop to plant
in the late fall because it can survive winter, grow in a variety of
soils and fight weeds.
Letting cover crops die
For cover crops to be beneficial to the soil, it is best to choose
ones that die on their own like Daikon radishes. When the radishes
die off, it helps soften the soil.
Cover crops like oats may die from the cold temperatures. However,
the dead oats still protect the soil.
There are additional benefits from allowing cover crops to die
naturally. Frillman says, “cold season cover crops like hairy vetch
and winter rye will grow in the fall, die back to the roots for
winter, and regrow in spring from roots.” The outcome is “improved
spring weed suppression and high amounts of biomass that will break
down into organic matter later.”
What is promoted that may not be beneficial in Central Illinois
Though cover crops are often seen as a way to improve soil health,
some research shows they may not always work as well as intended.
In two studies led by Nakian Kim, a doctoral graduate from the
Department of Crop Sciences at the University of Illinois, Kim
discovered “short-term use of cover crops can’t undo decades of soil
microbial dynamics in response to continuous corn and heavy nitrogen
fertilizer use.” Kim says, “In the Midwest, our soils are healthy
and resilient, but we shouldn’t overestimate them. A soil under
unsustainable practices for too long might reach an irreversible
threshold,”
In one study published in Agronomy, Kim analyzed “microbial
communities at the genus level.” This level of study helped Kim see
how “a soil and its microbial community are responding to soil
management practices.”
One discovery Kim made in this study is “both long-term
fertilization and cover crops favored microbes that could increase
the risk of nitrous oxide emissions.”
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A second study by Kim
published in Frontiers in Microbiology, “focused on nitrogen cycling
by identifying microbial functional genes in soil, rather than
characterizing microbes themselves.” Kim says this study showed
“[a]pplying a lot of nitrogen fertilizers definitely disrupted
nitrogen cycling communities.”
Among the negative aspects of
cover crops Kim discovered, he also found some positives. For
example, he points out, “cover crops also enhanced soil
biodiversity, as microbes with more diverse niches and functions
were associated with this practice.” As Kim says, “Details like
these – especially that cover crops can have both positive and
negative effects on soil microbes – may have been missed with the
broader microbial analyses of the past.”
Benefits of cover crops
For María Villamil, a researcher at the University of Illinois and
an American Society of Agronomy member, the benefits of cover crops
outweigh the drawbacks. In “Choosing the right cover crops to
protect the soil,” Villamil says you should choose cover crops “that
can survive the winter, grow a lot in the spring, and hold onto soil
that whole time.” While “some cover crops might slightly decrease
future crop yields,” Villamil says “in the long-term, protecting our
soil is worth it.”
Certain strategies need to be followed to reap the benefits of cover
crops. Villamil says “If we want to see benefits from cover crops,
we need to focus on managing our cropping systems for cover crops,
giving them room to grow, and using them strategically following
corn crops, or silage corn or even wheat, if we are lucky to have
this crop in the rotation.” To Villamil, the main goal with cover
crops “should be protecting the soil and leaving the soil nutrients
in place.”
Positive effects on soil are a significant benefit of planting cover
crops. An article on the Cover Crop Project from the University of
Illinois National Center for Supercomputing Applications says, “To
date, extensive research has found that adopting cover crops in the
fallow season of commercial row crop production can improve soil
health by, among other things, improving soil organic matter,
carbon, as well as water retention and some weed suppression.”
In deciding whether to plant cover crops, exploring and considering
both advantages and disadvantages is important. If carefully
managed, it seems the benefits may outweigh the drawbacks.
[Angela Reiners]
Resources:
Cover Crops: What Are They and How Do They
Work?
Let plants do the work, it's time to plant fall cover crops:
University of Illinois Extension
Consider cover crops this fall - University of
Illinois
Cover crops not enough to improve soil after
decades of continuous corn
Welcome to the Cover Crop Project
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