Crop Science Society of America
by Madeline Fisher
Organic farmers face quite a conundrum when it comes to controlling weeds. Fighting them with tillage instead of herbicides keeps chemical pollutants out of the environment. But tilling too much can damage the soil and hand-weeding is often prohibitively expensive, especially on larger farms.
What’s the best solution to this puzzle? Future answers could lie not only in new farm practices, but also in the crops themselves. Although still in its infancy, a movement is growing among U.S. plant breeders to develop crop varieties specifically for organic agriculture.
Crops like corn, soybean, and wheat have been bred for decades to thrive in production ag systems with chemical fertilizers and pesticides. Meanwhile, similar efforts on the organic side have been “quite limited,” says Bill Tracy, a University of Wisconsin-Madison sweet corn breeder. Organic farmers have learned to make do with conventional varieties of sweet corn and other crop plants, but the lack of alternatives raises a key question, Tracy says. “Are sweet corn hybrids or field corn hybrids that have been bred to grow with chemical inputs the best fit for organic agriculture?”
Tracy himself began considering that question only five years ago, after a grad student approached him about doing an organic breeding project. The new breeding program launched by the pair focused on the genetics of sweet corn’s ability to compete with weeds. It has since expanded to include many other traits as new students have come on board. “Like a lot of things in my research program, this was mostly student-driven,” Tracy says.
Besides being strong competitors against weeds, for instance, organic sweet corn varieties need to be naturally resistant to rust and other diseases, since combatting disease with chemicals isn’t an option. They also need to taste good (Tracy and his students are the flavor-testers), yield well, and possess strong stalks that won’t topple over in wind or rain.
Varieties that can germinate earlier in the year are also important. The sooner farmers can sow their corn in spring, the sooner they can bring it to market in summer—and the more money they can make. Sweet corn that goes for $5 per dozen in July, for example, may sell for $2 a dozen less in September when the market is glutted, Tracy explains. “So the first local corn is the most valuable.”
This is why Tracy’s students Adrienne Shelton and Tessa Peters are collaborating on a project with a Minnesota organic farmer named Martin Diffley. Their goal is to develop varieties that aren’t just flavorful and disease-resistant, but whose seeds germinate well in the chilly soils of early spring. And if that weren’t enough, Peters is also selecting for plants that tolerate crowding to try to boost sweet corn’s ability to suppress weeds.
“Weeds are such a big problem for organic farmers,” she says. “Every dollar they make on the organic premium is spent on manual labor—weeding.”
One issue she’s been running into, however, is that when corn plants grow closer together their ears get smaller. That’s because each plant gets less light and nutrients and thus has fewer resources to put into the ear. While field corn growers can make up for this size reduction by planting more plants and harvesting more ears, things are trickier in the sweet corn market. “The people who eat sweet corn don’t want the ear to get smaller,” Tracy says.
It’s this kind of hurdle that shows why it often takes years for breeders to create a new variety—and organic breeders have gotten a very late start. Still, the payoffs could be great, not only for farmers but also for the growing number of companies that depend on organic ingredients. Peters’ research, for example, is funded by a Seed Matters fellowship that’s supported by the Clif Bar Family Foundation. “So, private industry that benefits from organic is also starting to see that [organic breeding] can be really helpful to their end products,” Peters says.
As a long-time university plant breeder, Tracy sees yet another benefit. Unable to compete with the resource-rich breeding programs at private companies, public plant breeding programs at universities have been declining. Now, perhaps, organic breeding could offer a new niche, Tracy says. “Public plant breeders are looking for places where they can fit in, and I think organic breeding is one of those places.”
Shelton and Peters participate each year in the Student Organic Seed Symposium, a gathering aimed at fostering dialogue between students, researchers and industry professionals . For more information, visit: https://sites.google.com/site/studentorganicseedsymposium (this site seems to be down, apologies).