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Interseeding alfalfa into corn silage shows promise

The system addresses issues in corn silage and alfalfa rotations, but it comes with challenges.

Fran O'Leary, Wisconsin Agriculturist Senior Editor

May 30, 2024

3 Min Read
Corn silage being harvested
CORN SILAGE FIRST: After corn silage is harvested, the aim is to have a robust stand of alfalfa to provide ground cover during fall and winter and to quickly reach full production the following spring. FRAN O’LEARY

Seeding alfalfa into corn silage initially may not seem like a good idea, but Mark Renz, professor and Extension weed specialist at the University of Wisconsin-Madison, says this method addresses several issues in corn silage and alfalfa rotations.

“Rotating corn silage and alfalfa is a common practice for providing livestock forage,” Renz says. “However, alfalfa yields less forage compared to corn silage, which leads farmers to grow it less often. Corn silage can yield about 10 tons of dry matter per acre, whereas alfalfa, once established, might yield about 6 tons per acre.”

This yield gap is particularly evident in alfalfa’s seeding year, he notes. “Producers plant alfalfa in spring after growing corn or other crops for a few years,” Renz explains. “However, spring-seeded alfalfa requires much of the season just to establish before it can be harvested.”

One significant issue with corn silage is the lack of ground cover after harvest. This can lead to soil and nutrient runoff when manure is spread.

“Nutrients like nitrogen and phosphorus are entering waterways, causing pollution and soil loss, which impacts future crop production,” Renz says.

In the interseeding system, corn and alfalfa are planted simultaneously. After corn silage is harvested, the aim is to have a robust stand of alfalfa to provide ground cover during fall and winter and to quickly reach full production the following spring.

How to establish alfalfa

Follow these steps to establish alfalfa:

  1. Select an appropriate field. Ensure the site is well-suited for alfalfa production.

  2. Choose suitable varieties. Use glyphosate-resistant or conventional varieties of alfalfa well-adapted to growing under corn.

  3. Interseed early. Interseed alfalfa shortly after planting corn. Ensure the seedbed is firm and alfalfa is planted at the correct depth. Select corn varieties that will be ready to harvest by Sept. 1.

  4. Manage pests as needed. Ensure good weed control for conventional alfalfa varieties due to limited herbicide options.

Yield expectations

Successfully establishing alfalfa under corn silage can double the alfalfa yields in the first production year compared to spring-seeded alfalfa. Regarding corn silage yields, Renz’s research indicates variable outcomes. Some years show little to no yield drag, while other years there can be up to an 8% yield reduction.

“Interseeded alfalfa can delay corn development by up to four days,” he says. “Farmers need to monitor corn dry matter closely to harvest at optimal moisture and maximize yield.”

The timing of planting corn and alfalfa is crucial. Early-season corn planting can result in yield drag due to cool conditions that favor alfalfa over corn. On the other hand, later-planted corn is more competitive and may experience less yield loss.

“Try not to harvest these fields when it is wet,” Renz says. “If we harvest fields when they are dry, we get no yield reduction.”

Fertilizer management

Proper fertilizer management is critical, as interseeded alfalfa competes with corn for nitrogen and other nutrients. Applying adequate nitrogen is essential to maximize corn yield with interseeded alfalfa.

Ongoing research aims to refine fertilizer management and optimize the timing and rates for applying plant protection products. Identifying hybrid characteristics that enhance the system’s reliability and profitability is also a focus.

By addressing these factors, the interseeding system can be fine-tuned to produce high yields of both corn silage and alfalfa, making it a viable and sustainable agricultural practice.

Benefits and concerns

If management recommendations are followed, Renz says this system offers the following benefits:

  • Yields of intercropped alfalfa will increase by up to 12%.

  • Nutritive values of intercropped corn and alfalfa will be similar.

  • Profitability should increase.

  • Environmental footprint will improve.

However, Renz notes, there are a few concerns:

  • High corn yields and wet growing conditions can cause failure.

  • Corn silage yield could be reduced by 8%.

  • It costs $50 more per acre and is more time consuming than a traditional system.

Renz says a number of UW-Madison scientists and researchers have been involved in this project.

“We have been working on this for over 10 years,” he says. “We think it is a viable option.”

For more information about interseeding alfalfa into corn silage, email Renz at [email protected].

Read more about:

AlfalfaCorn Silage

About the Author(s)

Fran O'Leary

Wisconsin Agriculturist Senior Editor, Farm Progress

Fran O’Leary lives in Brandon, Wis., and has been editor of Wisconsin Agriculturist since 2003. Even though O’Leary was born and raised on a farm in Illinois, she has spent most of her life in Wisconsin. She moved to the state when she was 18 years old and later graduated from the University of Wisconsin-Whitewater with a bachelor's degree in journalism.

Before becoming editor of Wisconsin Agriculturist, O’Leary worked at Johnson Hill Press in Fort Atkinson as a writer and editor of farm business publications and at the Janesville Gazette in Janesville as farm editor and a feature writer. Later, she signed on as a public relations associate at Bader Rutter in Brookfield, and served as managing editor and farm editor at The Reporter, a daily newspaper in Fond du Lac.

She has been a member of American Agricultural Editors’ Association (now Agricultural Communicators Network) since 2003.

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