Iowa Public Television


Chance of La Nina Rising

posted on June 24, 2010

Widespread thunderstorms rumbled through most of the Grain Belt again this week, but forecasters are finally calling for drier and cooler weather over the next week to 10 days.

And while Will Rogers once joked that "everyone complains about the weather but no one does anything about it..." a couple from "south of the border" might beg to differ.

They're known as El Nino and La Nina, and experts say they play a major role in shaping U.S. weather conditions. Market to Market got a primer on the two patterns this week from one of the nation's leading climatologists. And as Laurel Bower Burgmaier explains, the weather guru said it appears El Nino could be yielding to his sister... La Nina.

Aaron Saeugling, Field Agronomist: "Weather's always a concern in corn and soybean production. It doesn't matter what part of the country you're in."

One weather pattern that has a lot of people talking is El Nino. But what exactly is it? And what can it mean for farmers in the Corn Belt?

El Nino is a weather pattern associated with warmer ocean currents off the west coast of South America and along the equator. Atmospheric pressure changes combined with warmer waters in the Pacific Ocean cause evaporation to accelerate. The phenomenon can fuel dramatic changes in normal weather patterns.

Aaron Saeugling is an Iowa State Field Agronomist at the Armstrong Research Farm in southwest Iowa.

Aaron Saeugling, Field Agronomist: "Crops across the Midwest are variable. I think most growers would say corn planting season started off with a bang. Then we got in a lull period in the tail part of April and the beginning of May when rain turned out in varying degrees across the Midwest. Some missed it the rains. Others like south central Iowa have been wet the whole season with areas still not planted."

Elwynn Taylor, an Iowa State University Climatologist, says just like everything else, El Nino has an opposite –a phenomenon called La Nina. Often, an El Nino can bring drier weather to the western Pacific and wetter weather in the East. La Nina can create harmful hot, dry weather conditions extending into the U.S. Midwest grain belt.

Elwynn Taylor, Climatologist: "During the past 30 days, we've seen a change from neutral conditions to .6 standard deviations on what we call the positive side of neutral. When it reaches 8 tenths, we have La Nina. We've gone two-thirds, three quarters of the way to a La Nina in 30 days. That's about as fast as we've ever seen things change."

The timing of La Nina's arrival is important regarding the risk it poses for row crops. Adequate moisture in July is critical for corn yields, while soybeans are more dependent on August rainfall. If La Nina conditions are reached in June, the likelihood of diminished corn yields becomes greater.

Elwynn Taylor, Climatologist: "When the La Nina occurs during the growing season, there's a 70% chance that the trend line will not be met by the yield. There's a 70% chance of a below trend crop yield in the Corn Belt. When there's an El Nino, there's about a 70% chance the crop will have an above trend line. When we have neutral conditions, it's close to 50/50."

Saeugling works with farmers from Interstate 35 to Nebraska and from Interstate 80 to Missouri. He says the main concern for producers is root establishment after the wet spring.

Aaron Saeugling, Field Agronomist: "A concern most producers might have into July and August are these roots substantial enough to carry these corn plants when we get into grain production? As root systems go, this is when we're going to make grain with this. It's going to have access to nutrients we've applied during the growing season. Here's an example of where nitrogen probably won't help this corn plant. He's just had too much water."

Despite ample moisture the past six months in much of the Midwest, history and emerging weather patterns indicate the faucet could suddenly shut off. Taylor says he is seeing a similarity between this spring and summer's weather with that of 1983.

Elwynn Taylor, Climatologist: "In 1983, we switched rapidly from an El Nino condition in the winter to La Nina in the summer giving us one of the worst droughts that we've had since the 1950s. It greatly reduced yields across the Corn Belt because we went from a wet spring to by the middle of July, the rain stops totally across the Corn Belt and we have a disastrous drought across the country."

Aaron Saeugling, Field Agronomist: "Right now, we're cooler and more moist than normal. So if we go the other direction and it gets hot and dry, those shallow roots are not going to provide moisture that the corn plant needs at a critical time. Beans tend to tolerate dry weather better, but on the negative side, they are under excessive moisture now."

Saeugling points out the hybrids used by farmers today compared to those used in 1983 have better stress tolerance. And he says many producers are changing the tassling and reproductive time of their crops, usually in hot, dry July, by planting much earlier.

Elwynn Taylor, Climatologist: "Farm management has greatly improved over the years. And the crops themselves have improved with science and plant breeding. So our yields have gone up. What we haven't changed is the variability in the crop yield during certain changes in weather."

While La Nina is associated with dry conditions in the Corn Belt, that doesn't mean a drought is imminent. With rivers currently brimming at their banks and water standing in fields all across the Midwest, it's a concept that many farmers find hard to believe.

Taylor says climatologists are paying close attention to the areas that are getting soaked by above normal rainfall. He thinks this could be a clue as to what may happen. He says the wet weather pattern usually moves up to the U.S.-Canadian border by June. But he also points out that it's currently being held down in the U.S. indicating perhaps a full-fledged La Nina soon.

And Taylor maintains while not every La Nina brings a drought, every drought occurs during La Nina.

Elwynn Taylor, Climatologist: "Since it's happened before and 1983 being the example, the answer is yes it may happen. It's happened 30 percent of the time. So, one third of the time that we switch from El Nino to La Nina in June, we do have stressful conditions, more stressful than average develop for the crops in the summer."

For Market to Market, I'm Laurel Bower Burgmaier.


Tags: agriculture crops news storms weather