Corn and runner beans combined: Good for animal feed, good for insects

Corn and bean plants together in one field: A method that has been practiced in South America for 2000 years is being attempted by more and more farmers here in Germany. The benefits are obvious: more food for bees and up to two percent more protein in the silage. But in the end, it primarily comes down to the type of bean.

I always thought that the corn plant would really suffer if I planted beans under it,” says Friedrich-Wilhelm Klopp, a farmer in the Gifhorn district. But his doubts about mixed cultivation have proven to be unfounded. In strolling through his densely covered field, he finds fully formed corncobs. Land planted with corn alone produces a rank-and-file formation of stalks, but Klopp's corn-bean field resembles a jungle of intertwining plants – in part because the stable corn stalks support the winding, climbing beans.

Klopp has an agricultural and forestry operation with piglet and pork production. He also holds shares in a biogas plant. Starting this year, he has been testing how corn and runner beans work together. But the concept isn‘t a new one. Just the opposite, in fact: Farmers in Central and South America have cultivated their fields this way for more than 2000 years. Since then, corn has flourished “together with other plants such as beans, squash and Andean lupin,” explains former KWS corn breeder Walter Schmidt. “Through a number of trials, we have brought the system to its current status and can now offer a practical solution.”

Raising protein content thanks to beans

Many other farmers also see the benefits of the combined corn-bean cultivation as an alternative to corn cultivation alone. A critical point in the combination of eight corn plants and four bean plants to one square meter is the higher protein concentration of the silage. The protein content of corn silage alone is approximately seven percent; when combined with runner beans, it can be raised to up to nine percent. “Among other things, this allows farmers to save on imported soy meal that is added to feed," explains Benjamin Simon, regional consultant for corn and rapeseed at KWS.

Reduced risk of soil erosion

Another benefit: Runner beans provide shade for the soil, thus suppressing weeds, and reduce the risk of soil erosion. The seed breeding institute in Hohenheim is currently conducting trials on the properties of the bean, aimed at exploring whether the bean's ability to absorb atmospheric nitrogen – in a cultivation system with reduced mineral and organic fertilization – is especially beneficial.

More food for bees

Insects benefit greatly from the combined corn-runner bean planting since bees and bumblebees have access to a wider range of food for a longer period of time: While corn flowers for just a few days, runner beans flower later than corn and for several weeks. The mixed cultivation thus also contributes to a more varied agriculture and represents an alternative to monocultures in the fields.

Despite its many advantages, mixed cultivation has a few disadvantages as well. Some types of beans have a higher phasin content – a protein that is toxic for people and animals in higher concentrations. This is why beans are cooked before human consumption: Cooking denatures the phasin to make it nontoxic. However, there are few findings that show its impact on the health and performance of animals. “To play it safe, we looked for types with low phasin content,” explains Walter Schmidt, former corn breeder at KWS and now a consultant.

More than 250 types were tested at the Chair of Animal Nutrition in Weihenstephan. With success: The tests identified a suitable type of bean. It has "an extremely low content of less than five milligrams phasin per kilogram of organic dry matter," says Schmidt. Related trials at the Chair of Animal Nutrition in Weihenstephan demonstrated that the gastric liquids in cow bellies actually break down the phasin.

Corn-runner beans silage not a problem for biogas installations

Silage made from corn and an appropriate type of bean thus benefits animals as feed. And it is also entirely possible to produce regenerative energy with corn-runner bean silage. This is an important point for farmer Klopp and his biogas plant, which can easily be operated with corn-bean silage.

Klopp summarizes: “The bean and corn combination is a good alternative and it looks like it will establish itself here in the future."

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