How Drought Kills Yield

How Drought Kills Yield

The promise - and limitations - of drought-tolerant seed technology

With an epic drought on everyone's mind, I met last week with David Warner, Pioneer Hi-Bred International's top man in drought tolerant seed technology.

In the back of my mind, I hoped he would share something that would give people a little hope for the future.

He did. But with a big caveat.

"There's definitely opportunities for tech gains in drought technology for the more common types of stresses we see," says Warner, "but in a year like this, when it's catastrophic with weeks without rain, no technology will make much impact. There is no technology for a cactus corn plant."

"Eighty million acres have some level of drought stress this year," says Dave Warner.

Warner joined Pioneer two years ago as program leader for agronomic traits. He manages the RD pipeline from early research to product strategy with special focus on nitrogen efficiencies and drought tolerance. Before joining Pioneer he spent 25 years working on drought tolerance research, primarily at DeKalb Genetics Corp., a Monsanto company.

So all-consuming is the dry weather, it's hard to remember that every year about 85% of U.S. corn acres are, at some point, impacted by yield-limiting water supplies, he says.

"Even in years with what seems to be adequate rainfall, there's room for improvement to handle those types of water stress," he says.

From a timing standpoint, drought that occurs as it did this year right around flowering can be devastating, because the corn plant is most sensitive during early stages of flower development to mid grain-fill, or the dough stage. "If the drought occurs right at flowering, we can lose up to 6 bushels per day," he says. "During grain-fill it's more like 3 bushels a day."

Drought stress at flowering can cause yield loss potential of 6 bu. per day.

Why? In a drought, ear silking slows dramatically, but the plant continues to develop its tassel and pollen shed; as a result, the plant sheds pollen on ears with little or no silk, so pollination drops to zero -- and so does yield.

"Farmers know ten days after flowering what they have in the field," says Warner. "If the ear has not produced silk and the plant is done shedding pollen, they're done – there won't be much yield."

Even farmers who have irrigation will see lower yields if they experienced extreme heat this summer. At higher temperatures plants transpire faster and go through more water.  "If you have 70-degree days combined with dry weather it's a lot better than 100-degree days and dry weather, because the plant does try to cool itself down through transpiration and needs more water to do that," he explains.

Drought-tolerant seed launched

After many years in the research pipeline – both traditional plant breeding and transgenic - the seed industry is now launching drought-tolerant seed on commercial farms.  About 250 farmers in the western Great Plains this spring were first to plant Monsanto's drought-tolerant corn, DroughtGard, on about 10,000 acres as part of on-farm trials.

DroughtGard, developed through transgenic research, was approved by USDA last December. According to USDA's Final Environmental Assessment, the seed may improve yields over conventional hybrids in moderate drought conditions by 2.76%.

Last year Pioneer put out 8,000 on-farm field trials of its drought-tolerant seed, AQUAmax, with five hybrids targeted for the western Corn Belt.  Those results were encouraging: at the 680 sites classified as drought stressed the hybrids showed about 7% yield advantage over other hybrids, says Warner, "but we're finding they also perform well in ideal conditions, too.  In the remaining non-stressed locations the hybrids showed a 3% advantage."

Aquamax hybrids were planted on 2 million acres this year and the company has launched an additional class of those hybrids to give growers more options on relative maturities.

Monsanto's line was developed using genetically modified technology while Pioneer's hybrids were developed using something the company calls "accelerated yield technologies," a suite of different tools that include native traits, gene markers, molecular breeding as well as managed stress field testing locations. Pioneer is also doing transgenic research, but Warner does not expect that drought-tolerant technology to be launched until sometime in the next decade.

I suspect drought-tolerant hybrids from both companies will attract a lot of attention this fall. Meanwhile, the 2012 drought is grinding far and wide into the Corn Belt.

"Eighty million acres have some level of drought stress this year," says Warner. "It's amazing. I've never seen a drought this bad in my entire career, and the thing is, it's really hitting the heart of the Corn Belt, from Kansas through Indiana."

No one wants to see another year like 2012, but researchers are planning for more years like this. Just don't expect miracles. There won't be a silver bullet GMO that suddenly saves us all from future droughts. The more likelihood is incremental gains using conventional plant breeding, native markers and possibly some GMOs.

"It takes several years to produce these products," says Warner. "We can't just turn on a light switch."

Keep up on the 2012 Drought by visit The site features a round up of key drought news from across the country and daily video updates from Farm Broadcaster Max Armstrong, Farm Futures Senior Editor Bryce Knorr, Agricultural Meteorologist Greg Soulje, and more.

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