Recent concerns over insufficient corn  and soybean  supplies for 2011 could intensify if Midwest weather proves unfavorable for corn and soybean production this spring or summer. Yet, the current La Niña weather system that has prevailed since April 2010, is likely to pose little threat to Midwestern corn and soybean yields this year, according to Harry Hillaker, Iowa state climatologist.
“The impact from a La Niña weather system on crop production in the Midwest varies quite a bit depending on their timing and how long they last,” says Hillaker. “This La Niña is very different than the one during 1988 that everyone thinks about as being associated with severe drought conditions.”
Cool Pacific water temperatures off the Peru coast dictate La Niña weather conditions that can impact temperature and rainfall patterns in many parts of the globe. “The current La Niña is likely to begin fading as we head into spring, and historically fading La Niña events have given no consistent signal for the type of Midwest growing season weather to expect,” says Hillaker. “Yet, there is a hint of a tendency for such events to favor a warmer- and drier-than-usual growing season for us.”
Still, the current La Niña has some similarities with another one that occurred only a few years ago, he adds. “The 2007-2008 La Niña is the most recent corollary to the La Niña we’re seeing now,” says Hillaker. “In 2008, Iowa had a ridiculously wet, late spring and early summer, which caused a lot of flooding issues. However, the rest of that year was fairly favorable for crop production.”
This year, Iowa and the northern Midwest states will likely be going into spring with plenty of subsoil moisture again, Hillaker points out. “The northern Corn Belt states have been really wet and snowy this fall and winter, in sharp contrast to the eastern Corn Belt and states west and south of Iowa, like Nebraska, Kansas and Missouri,” he says. “For Iowa, we’ve had four very wet years in a row, from 2007 to 2010; so, even a normal growing season would be quite a change for us.”
The current weather outlook for Iowa is that March will slightly favor cooler-than-normal weather and April will have stronger odds for wetter and warmer-than-normal weather, says Hillaker. “For the summer, we will likely see one unusually warm month,” he adds. “Yet, there are no strong tendencies for the summer as a whole.”
Corn and soybean growing areas in the northern Corn Belt will likely stay too cool, too long, for an early start to planting, however, says Drew Lerner, World Weather, Inc. , meteorologist and owner. “This spring, we’ll likely see colder-than-normal conditions prevail in the Upper Midwest and delays to spring planting,” he says. “Right now, the big snow deposits are in North Dakota, Minnesota, Wisconsin and northern Iowa. In these areas, it will likely be slow to warm up and for snow to melt come spring.”
Flooding could also be an issue for parts of the Corn Belt in 2011, he adds. “In the Upper Midwest, the flooding potential will probably come down to how quickly the snow melts,” says Lerner. “However, as we move toward spring, colder-than-normal weather is likely to remain in the northern Great Plains, while a wetter-than-normal weather pattern will likely evolve in the Ohio River Basin and northern Delta. Both areas will have a wetter-than-usual bias for a little while during spring, but neither is expected to persist into a serious problem.”
While the entire Corn Belt is likely to be slow to warm up this season, the southwestern Corn Belt won’t likely be nearly as wet as the Corn Belt as a whole, says Lerner. As a result, Midwestern “corn and soybean growers in the east and north may experience more of a delay in getting planting done than in the southwest,” he points out.
Unlike a fair number of other meteorologists who may have a different view, Lerner says he believes the current La Niña system will last throughout the entire 2011 growing season. “If that occurs, this will give us a warmer and drier bias during early summer, particularly in the southeast,” he says. “That dryness will work itself from the southeast into the northwest as the summer goes on. So, that warmer-than-usual and drier-biased weather will likely be coming into Wisconsin, Minnesota, Iowa and northwestern Illinois during late July and August.
“The bottom line to all of this is that if farmers in these areas are late in getting their crop in the ground this spring, their corn and soybeans will be more vulnerable to summer dryness, particularly in the northwestern Midwest,” adds Lerner.
Still, just how much La Niña will impact crop production comes down to timing, Hillaker notes. “We can talk about general tendencies of a La Niña with a fair amount of certainty, but the timing of when rains may come or when temperatures may change significantly is way beyond what we’re able to do right now,” he says. “It’s the timing of those events, and not so much the general tendencies, that can have the biggest impact on crop production.”
For more information about La Niña weather systems, visit the following Climate Prediction Center website .