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Weather outlook 2018: Inversions, La Nina and growing degree days featured in Taylor’s presentation

-Messenger photo by Kriss Nelson
Chuck Amberg of Bird Island, MN and Randy Peltz of Ringsted visit with Elwynn Taylor after his presentation on the 2018 weather outlook at the Farm News Ag Show.

A packed room listened to Elwynn Taylor, Iowa State University climatologist, give his annual forecast Wednesday at the 16th annual Farm News Ag Show.

Presenting his thoughts on the weather outlook for 2018 and beyond, Taylor also provided producers with some tools to help better manage the risk for their crops.

Inversion

Inversion is an issue that was at the forefront of the 2017 growing season that is believed to have been behind a lot of off-target movement of herbicides, specifically dicamba, that caused damage to over 3.6 million acres of soybeans.

An inversion, Taylor said, could cause the chemicals that have been sprayed to hang in the air above the field and get secondary movement into the air, causing them to potentially be sent to a field that is untargeted.

-Messenger photo by Kriss Nelson
Jamie Hefley of Fort Dodge reaches out to catch a pancake tossed to him by Randy Fosburgh during the annual pancake breakfast at the Farm News Ag Show.

Those inversions that are at shoulder high or higher, Taylor added, are the ones producers should be concerned about.

“Labels have read that if the wind is less than five miles per hour you need to check to see if there’s an inversion,” he said. “I would say if the wind is measurable you don’t have an inversion, because we can’t measure wind under three miles per hour, typically.”

If the wind is very still, Taylor said there very well may be an inversion. In those conditions, he suggests paying attention to the herbicide’s label, but he said to remember the rule that if it is perfectly still there’s a high chance there is an inversion.

Producers and applicators need to be aware of that, he said.

“Assume if it is perfectly still and there is a blue sky, assume there is an inversion there,” he said.

Taylor said generally the inversion will start when the sun goes down.

“The last hour of sun in the evening is when the inversion will begin,” he said. “If it is a still evening and there is a clear sky, an inversion will persist all night long.”

Taylor suggests buying a tool that will help to measure wind.

“These are amazingly accurate if you keep them clean, and reasonable in cost,” he said.

La Nina

“Right now we have a La Nina in place,” he said, “and a La Nina is not our friend in this part of the U.S.”

Taylor said when there is a La Nina present, there is a 70 percent chance of a below trendline yield. This particular weather pattern, he said, affects the Corn Belt here the same way it affects the Corn Belt in South America.

“But they are not as sensitive to it as we are here because they have 5 percent more rain than they need,” he said. “We get exactly the amount of rain we need if we have an average year. If South America is 5 percent dryer than usual, that’s ideal. If we’re 5 percent dryer than normal, we have a problem.”

What effects could another weather tragedy such as in the Dust Bowl have on our crops?

“Remember in the Dust Bowl years, like 1936, the weather that would cut the yield in half then will cut the yield in half now,” he said. “Our crop is just as sensitive to weather now as it was then. The same weather will have the same effect on the crop.”

Taylor added that although there are now better yields — and that’s a great improvement and will be a lot better for the people and industries that depend on our corn and soybeans — a half of a crop is still a half of a crop.

The weather trends, Taylor said, have shown for centuries that we will experience 18 years of stability and 25 years of volatile times. We are now into those 25 years where we could experience volatile weather.

“Now is the time to prepare for that type of management — knowing we are going to have high volatility,” he said.

Another weather trend is showing on average every 89 years brings the worse year of a century. This trend has been shown for more than 600 years of records made from tree rings, according to Taylor.

Taylor said the peak of the Dust Bowl was 1936, which brought the worse year of that century.

In the previous century, 1847 was the worse year for areas like Iowa and Illinois of the 1800s.

“That’s 89 years apart,” he said. “If this continues, we can expect to have the worse year of this century in 2025. This is the time to start to manage your risk in production and marketing.”

Predicting trendline yields

Taylor recommends when trying to predict the outcome of a growing season, always consider the percent of the trend.

“Don’t’ think about bushels until you think about selling,” he said. “If you wanted to compare the yield of this year to the yields five years ago, don’t compare bushels from year to year — compare the percent of the trend.”

Taylor suggests using the county’s trendline yield to compare to yields on your farm and insure the one with the greater volatility.

“If your farm is real consistent, insure the county; if your farm is real volatile compared to the county, insure your farm,” he said. “You just as well make some money on that thing or at least not cost as much to have the insurance.”

Growing degree days

Taylor said paying attention to growing degree days can also help determine what type of yields to expect and help manage risks.

“If we got 100 growing degree days to 200 behind usual at silking date to dent date, we’re going to have much higher yields than people are expecting,” he said. “Getting behind on growing degree days stretches out the number of days the plants are in the sun gaining the weight we sell.”

This, Taylor said, compares to having a steer on finishing rations longer, because it is taking longer to get from silking to dent.

Putting more growing degree days into a growing season from silking to dent may not mean very good results.

“Whether we are ahead or behind growing degree days after silking, you’ll know the yield,” he said.

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