On Expanded Corn Acreage: Less Crop Rotation, More Trait Rotation

Rotation of Seed Traits Encouraged in Corn-on-Corn Systems

GOLDEN VALLEY, Minn. - August 21, 2007 -- First it was crop rotation. Then it was herbicide rotation. Now, crop specialists are emphasizing trait rotation as farmers plant more corn-on-corn to keep up with the growing ethanol demand.

"We've witnessed a historic shift in the Midwest, with total corn acreage increasing by nearly 20 percent over 2006," says Tracy Mader, marketing manager for Agrisure® Corn Traits, Syngenta. "Many of these new corn acres were planted into last year's corn crop, which raises the importance of trait rotation to maintain yield potential while optimizing weed and insect control."

Cultivation is currently the only post-emergent control option for volunteer corn in conventional corn hybrids. Mader says that makes herbicide-tolerant varieties very desirable for second-year corn-not only for weed control, but also for convenience.

"Agrisure GT, for example, allows for glyphosate application to control non-GT volunteer corn, while Agrisure CB/LL allows for control of conventional or GT hybrid volunteer corn with LIBERTY® herbicide (glufosinate)," says Mader.

Like soybeans, corn can suffer significant yield loss through competition from volunteer corn. In a University of Illinois study, volunteer corn infestation reduced yield of GT and LibertyLink® (LL) corn by 42 percent and 60 percent at two Illinois test locations (Urbana and Dekalb) compared to GT corn plots treated with glyphosate and LL corn plots treated with glufosinate.

"Because the test plots were uniformly seeded with volunteer corn, these yield losses may be higher than what you might see under field conditions," points out Aaron Hager, University of Illinois extension weed specialist and coordinator of the study. "In the field, volunteer corn infestations usually include some combination of clump corn, which is not as competitive. But that doesn't change the take-home message, which is that volunteer corn must be controlled to prevent yield loss in corn-on-corn."

At the Dekalb facility, glyphosate provided complete control of volunteer corn in GT corn plots and yielded 219 bushels per acre. Glufosinate provided 90 to 92 percent control of volunteer corn in LL corn plots and yielded 205 bushels per acre.

"If your second-year corn follows a conventional hybrid, then you can use your choice of GT or LL corn to expand your weed control options," says Mader. "But when your second-year corn follows a herbicide-tolerant hybrid, trait rotation becomes essential."

Agrisure GT/CB/LL and Agrisure 3000GT (GT/CB/LL/RW) stacked traits combine glyphosate tolerance with glufosinate tolerance, leaving open the choice of over-the-top weed control. Mader says the combination gives growers the flexibility of using either glyphosate or glufosinate on volunteer corn based on the level of weed pressure and the previous year's corn traits.

Taking the lead in trait rotation, Syngenta is also emphasizing the importance of soybeans in the trait rotation equation. "Planting soybeans every third year gives you the agronomic advantages of crop rotation and provides an opportunity to clean up herbicide-tolerant volunteers with alternate chemistry," adds Mader. "It's a critical step in volunteer corn management."

In time for 2007 planting, the EPA approved Agrisure CB/LL/RW, a triple stack corn trait that combines glufosinate tolerance with industry leading rootworm and corn borer protection. The Agrisure RW trait, available individually and in stacks, is fully approved for planting in the U.S. Syngenta is taking all necessary steps to obtain Japanese export approvals for Agrisure RW as quickly as possible, and implemented a comprehensive grain marketing program for 2007 to direct the grain to domestic use markets such as livestock feed.

For 2008 planting, Syngenta will add Agrisure 3000GT, a quad stack that provides rootworm protection, control of European corn borer and tolerance to both glufosinate and glyphosate herbicides. In addition to these new stacks, Syngenta is currently developing additional traits to enhance corn-on-corn production, including broad lepidopteran control, drought tolerance, nitrogen utilization, second-generation corn rootworm resistance and amylase corn for enhanced ethanol production.