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Make corn see the light

There’s a yield reward if you keep the shadows off your emerging corn.

Special traits may need special care – especially tight weed control – to milk the most benefit from the trait, according to new Canadian research at Ontario’s University of Guelph.

Built-in shade avoidance is the issue, as the coleoptile emerges into daylight. When an emerging shoot detects a change in 

lighting, it triggers internal changes to avoid competition. This is a one-way street that costs seedlings energy and contributes to a rapid loss in yield potential.

How It Works  

Professor Clarence Swanton published the groundbreaking study in 2010 in a peer-reviewed scientific journal and followed up in 2012 with further discovery. 

He found the change in light quality (shade) caused by nearby weeds produces stress with permanent yield impact. If a seedling in sunlight is shaded partially, intermittently, or for a couple hours, it can set back the yield potential by bushels per acre.

Weeks later, during the flowering period, stress from very dry growing conditions can sap yield potential up to 8% per day (some hybrids handle it better than others). Those drought-tolerance genetics are closely tied to the reproductive anthesis-silking interval (ASI). 

In 2011, Swanton wondered about possible connections between the drought-tolerance trait and weed-control timing. 

“Knowing that the simple presence of a weed at corn emergence can influence the root structure of a corn plant, we wanted to test whether there was a chance you could lose the benefit of this novel trait in drought-tolerant plants if you delayed your weed control,” he says. 

Without waiting for drought conditions, Swanton proposed to test whether stress from weed competition could influence the ASI.

Graduate student Andrew Reid tested two nearly identical lines of corn from Syngenta. One hybrid with Agrisure Artesian technology was able to maintain its yield longer in very dry conditions and had a short ASI. The other was a near-isoline, without the drought-tolerant genetics. 

In 2011 and 2012, Reid’s research at two locations included seven different timings for weed control. 

Increasing stress by delaying weed control affected both hybrids. However, the drought-tolerant hybrid maintained a shorter ASI, lower kernel number, and higher kernel weight than the nondrought-tolerant hybrid.

They concluded that the drought-tolerance trait is not a yield-reducing burden in good growing conditions.  

“The take-home for the grower is, if you are interested in having this novel technology, you need to be aware that the way you manage weeds can potentially influence the effectiveness of the trait,” Swanton says.

“Weed-control timing can influence the length of ASI. To fully benefit from a novel trait, early-season weed control is very important,” he says. “Any weed competition – from the day the corn coleoptile breaks ground – will rapidly reduce yield and may limit the effectiveness of drought-tolerance traits.” 

Although the connections have only been demonstrated in one corn hybrid, Swanton notes that it may apply to traits in other crops.

“The principle of early-season weed control is important across all cropping systems. Corn is the lead for novel-trait expression. If you need the novel trait to be present, it’s probably relevant in canola and soybeans, as well,” he says.

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