During my travels across Indiana and the Upper Midwest, I love looking at crop fields. But I often wonder why I don’t see different types of crops. The usual answer has to do with making money with commodities and producing bushels. However, on-farm research and practical experience from farmers have shown us time and again that more diverse crop rotations can improve yields, minimize risk and increase overall profitability of the system. So, are you and your crop rotation ready for a paradigm shift?
A field experiment running since 2002 at Iowa State University found that when a two-year crop rotation of corn and soybeans was compared with three- or four-year crop rotations, yields were maintained or increased in the longer rotations. These long-term field studies compared the standard two-year rotation with three-year rotations that had oats interseeded with clover, and four-year rotations with oats interseeded with alfalfa grown for an additional year.
Corn yields averaged 5% higher in the three- and four-year rotations; soybeans averaged 25% higher. Along with yields, net returns also increased.
Researchers also saw a reduction in soil erosion, and nitrogen and phosphorus runoff losses. ISU and the Leopold Center for Sustainable Agriculture found that a more diverse crop rotation, in conjunction with no-till and reduced-till practices, reduced soil losses by 91% on the most erodible soils.
Certainly, you’ve noticed those lighter-colored hilltops — that’s loss of topsoil and organic matter. Those eroded hilltops infiltrate and hold less water, so crops dry out quicker. Rills and gullies start in these areas, and they’re less productive overall.
That doesn’t have to be the case. Don’t you think 91% less soil loss on these areas could make a difference?
Similar long-term research from the University of Wisconsin has shown that extending the crop rotation even out to a three-year rotation of corn, soybeans and wheat improved the yields of all crops. However, the sequence in the rotation was the key factor. A comparison of the rotation found that all crop yields improved when the sequence was corn, then soybeans, then wheat and back to corn again. If the sequence was different, all crop yields improved less.
John Tooker and others from Penn State University published research in April comparing diverse crop rotations that use strategic Integrated Pest Management practices and only apply pesticides when necessary to low-diversity, two-year crop rotations that use conventional insecticide applications. They found that not only did the two systems have comparable yields, but also the increase in predatory insect diversity in the more complex rotation benefited the cropping system within three years.
Why do we only see corn-soybean rotations today? If you go back into the archives and look at data showing percentages of harvested corn and soybean crops over time, you would see that even in the 1970s, parts of the eastern and central Corn Belt had 70% to 90% of their harvested acres as corn and soybeans. There has been a big push to simplify and streamline cropping systems over the past 50 years.
The 2017 Census of Agriculture shows that the majority of farmers in the eastern and central Corn Belt fall into the 35-to-64-year-old age group. This is a large age span with varying levels of life experience to mesh into one group.
Some of these farmers were farming in the 1970s when more diverse crop rotations were around, while the younger end of this group has only been farming with a two-crop rotation as the norm. Some have forgotten, and others never had the chance to learn about crop rotations.
Why a paradigm shift now?
Farmers aren’t alone when they question how to be profitable in the current system. Diversity is making a comeback. Many farmers across the country are adding a third crop to their rotation. Here in Indiana, farmers have planted nearly 1 million acres of cover crops across the landscape every fall for the past five years, making cover crops the third most-planted crop in Indiana. Granted, most of these acres are in a two-year crop rotation, but cover crops are an excellent way to start adding diversity to a cropping system.
Farmers who focus on healthy soil understand that diversity is essential to a resilient farm. The four soil health principles are:
- minimizing soil disturbance
- maximizing soil cover
- maximizing biodiversity
- maximizing continuous living roots
Recently released soil health case studies from the American Farmland Trust found that when using soil health management systems, not only did farmers see an increase in yield, but they saw a decrease in their risk and input costs. They also saw an improvement in their profits, all while providing a benefit to their natural resources. These case studies can be found at farmland.org.
The learning curve may be steep when it comes to fully realizing the crop rotation paradigm shift, but farmers are more willing than ever to share what they’ve learned with other farmers. If you’ve been wondering if you and your crop rotation need an adjustment, take time to seek out others implementing these changes.
You can find these farmers on large web-based platforms across the country, but don’t forget to look in your own neighborhood. The proximity of a nearby mentor can really improve your learning and your success in shifting the rotation paradigm.
McLain is the state soil health specialist with the Natural Resources Conservation Service in Indiana. She writes on behalf of the Indiana Conservation Partnership.