Fall 2016 Logan County
Farm Outlook Magazine

The benefits of crop rotation
By Derek Hurley

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[November 03, 2016]  In the last few years, farmers across the country have continued to plant corn in the fields. For years, corn made more money for farmers because of relatively high prices per yield when compared to other crops, such as soybeans. Due to lower prices on corn and higher prices on beans, many farmers could be looking into crop rotation.

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 more.

Works cited:

Butzen, Steve. “Best Management Practices for Corn-After-Corn Production.” Pioneer

“Diplodia Stalk and Ear Rots in Corn.” AgAnyTime

Peltier, Angie. “Disease Alert: Diplodia Ear Mold in 2016.” University of Illinois Extension, 11 August, 2016


Read all the articles in our new
Fall 2016 Logan County
Farm Outlook Magazine

Year in Review 4
Sustaining the farm 6
On-farm storage helps with profitability in 2016 10
How commodity prices and profits are affecting equipment sales 15
Agricultural science and technology:  Have we gone too far? 15
The benefits of crop rotation 22
Finding some profit:  The benefits of growing organic corn and soybeans 26
Growing alternative crops for more profit 32
Is the Illinois Nutrient Reduction Strategy counter intuitive to profits? 41

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