So, the questions are: what happens when we only plant corn for
so long? How will it help to change things up now?
Crop rotation is important for farming because of its effect on
soil. While plants and crops are able to replenish some nutrients to
soil as they grow, replenishment diminishes over time if the same
crop is planted, as it draws on the same nutrients over and over,
draining the soil and reducing its quality.
Corn, for example, can be described as a very thirsty crop. Corn
draws a lot of water out of the soil, and it requires a lot of
fertilizer to maintain healthy growth. This is because corn also
requires a lot of nitrogen to grow. Planting more corn year after
year will require more fertilizer with higher nitrogen
concentration. Growing more corn also comes with a risk of depleting
phosphorus in the soil. This may not seem problematic in the short
term, but it should be monitored in the long term, as phosphorus is
especially helpful for corn crops in the early stages of planting.
Another problem for farmers that can be mitigated with crop rotation
is weed control. After continuous seasons of corn planting, some
weeds will become more difficult to control, as they have adapted to
the same conditions after multiple years.
Rotating crops creates a different environment for weeds, making it
harder for them to adapt to conditions. Additionally, rotating in a
new crop requires different herbicides and weed killers, which
provides an opportunity to remove old, stubborn weeds from previous
seasons. Rotating herbicides is useful in weed management, as it can
prevent a long-term problem of weed resistance.
A third reason to consider rotating crops is to prevent disease.
Continuous corn planting increases the amount of leftover corn
residue left behind in the fields. This residue is a haven for
pathogens and diseases that will wait for the next growing season to
latch on to corn crops. One of these diseases is Diplodia.
This year, Diplodia has proven to be a nuisance for Illinois
farmers. Figures from the University of Illinois indicate that
Stenocarpella maydis, the fungus that causes Diplodia, has been
sighted more frequently this year. Diplodia infects corn ears after
the beginning of the silking stage. Diplodia overwinters on leftover
corn debris, which means that it can survive cold temperatures and
reappear the next year.
What does this mean for farmers who find Diplodia in their crop?
Diplodia causes a straw-brown discoloration of the lower portions of
the ear. Stalks will begin to lose firmness, and small black dots
begin to appear on the kernels. As a result of these symptoms, corn
kernels and stalks become brittle and lose mass. Infected corn may
not harvest completely, breaking away during the process and
reducing the overall harvest size. A reduction in weight comes with
a reduction in nutritional value, which makes the corn harder to
sell. On top of that, grain elevators may discount what they pay out
to farmers because of the fungus.
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So what can the farmer do to prevent Diplodia in the future?
If Diplodia is an issue, corn can be harvested early to prevent
further spread of the fungus. Keep infected corn separated from
healthy corn in storage. There are fungicides available that treat
Diplodia, and tillage can help reduce the presence of the fungus in
the soil by breaking up leftover corn debris.
But the best way to treat Diplodia is to try and prevent it from
growing in the first place. The best way to prevent Diplodia is to
rotate crops away from corn after a year or two. Consider planting a
different crop for another year or so before returning to corn. This
gives the soil time to recover nutrients, prevents weeds from
developing resistances, and reduces the amount of corn debris that
could result in Diplodia infections.
Even at lower prices, many farmers stick with corn because of sheer
volume of harvests. But after years of continuous corn planting, we
are only now beginning to see the side effects of such a planting
strategy. When you combine falling prices with increased funguses
and a lower quality of soil, a question of investment arises. Is it
better to risk more investment in treating funguses and buying
fertilizer to grow more corn, or would it be worth the risk to
rotate to a different crop?
Despite the low prices on corn and the resulting glut of planting so
much of it in the last few years, rotating away from corn is still a
risky move, but so is the continuous planting of corn and nothing
“Best Management Practices for Corn-After-Corn Production.” Pioneer
“Diplodia Stalk and Ear Rots in Corn.”
“Disease Alert: Diplodia Ear Mold in 2016.”
University of Illinois Extension, 11 August, 2016