Weak El Nino conditions are expected to persist at least into May and June, helping 2015 corn and soybean crops get off to a good start in the Midwest. "That will get us started, but we need the El Nino to persist through July for the U.S. to have a 70% chance of an above trend yield," says Elwynn Taylor, Iowa State University Extension climatologist.
His early corn yield forecast is based on the favorable El Nino outlook and generally good soil moisture conditions heading into planting season. His best guess is for the U.S. to average 165 bushels per acre in 2015, if we have normal weather.
Taylor is projecting a range of 164 to 166 bushels per acre, about 3 bushels above USDA's projected trend line yield of 162.3 for 2015. The trend line is based on USDA's annual estimated final harvested yields for the past 30 years.
El Nino is weak but may be strong enough to produce big crop
The summer El Nino outlook is usually more certain by April 15 when farmers are ready to plant, notes Taylor. "When an El Nino occurs, we have a better chance of a big U.S. crop than when we have a La Nina," he explains. "We currently have a weak El Nino, but it may be enough to produce favorable weather conditions for crops in Iowa and the Corn Belt this year."
El Nino weather conditions occur when surface waters of the Pacific Ocean near the equator become warmer than usual. La Nina weather occurs when the water is cooler. The current El Nino has been slow in developing and the warmer waters aren't in their usual location along the equator. The National Weather Service announced in early March that an El Nino, although weak, is now in place. It could possibly strengthen or it could weaken, too.
Above-average rain last fall disrupted harvest for some farmers, but it recharged soil moisture reserves and Iowa has a good supply of soil moisture going into the new growing season. About 80% of the sites checked in Iowa last fall had full soil moisture profiles, estimated at 10 to 12 inches of water in the top 5 feet of soil. Taylor says 25 inches of water is needed for optimal corn and soybean yields with normal summer temperatures.
Much of Midwest has good supply of reserve subsoil moisture
"We're in good shape in Iowa and much of the Midwest going into planting season, as we have about half the water we need for an average yield," he says. "With normal weather during the growing season, and timely rains, the odds favor having a good year. Rains need to be timely, however. It doesn't help if it all comes in one weekend. But the odds are improved of having a good year in 2015."
While this year's outlook is starting out favorable, long-term cycles suggest farmers are likely to experience more weather risk over the next two decades. "The weather is becoming much more volatile now compared to the last 20 years," says Taylor.
What kind of planting season weather will Iowa have? Taylor watches Arkansas during March for clues. A wet March in Arkansas means Iowa will likely be wet in April and May. In March 2015, Arkansas has had significantly more rain than normal.
Will Iowa have a wet or a dry planting season this spring?
"The weather in Arkansas, Louisiana and Tennessee has been really wet the past 30 days," notes Taylor, at the end of March. "Rainfall has been two to three times normal, all the way from south Texas, including Arkansas and up the Ohio River Valley. All of that area is wetter than usual. This greatly enhances the chance of having excess precipitation at planting time in Iowa."
However, there is a conflict in the atmosphere this year. Low pressure persists in the Gulf of Alaska, reducing the chance of precipitation in the area north of St. Louis and west of Chicago: that's Iowa and northern parts of Missouri and Illinois, and into Nebraska, Minnesota, the Dakotas and parts of Wisconsin. "If the low pressure area in the Gulf of Alaska persists, along with the chances of having very wet conditions coming into Iowa from Arkansas, we'll have to wait and see who wins," says Taylor. "Will it be wet or dry in Iowa this spring?"
Keep an eye on Gulf of Alaska to see if it offsets wet effect
When these two conflicting weather situations -- wet in Arkansas and low pressure in the Gulf of Alaska -- have occurred simultaneously in the past, who won? "It happened in 1988 and 1989 and Gulf of Alaska won," says Taylor. "We ended up with drought conditions for more than 12 weeks in Iowa in 1988 and it was a serious drought. In 1989, the drought was even more serious for farmers in western Iowa."
The drought of 1988 affected the eastern Corn Belt and reached into the eastern half of Iowa, ending at Interstate 35. The drought of 1989 was west of I-35 with Illinois, Indiana and Ohio recovering. Iowa had drought both years, but the drought of 1989 was concentrated in western Iowa and states west of Iowa.
Situation now is similar to 1988, uncertain about this spring
"The situation we have now is very similar to 1988," says Taylor. "It's uncertain what will happen this spring; will it be wet in Iowa in April and May or will it be dry? We'll have to watch that low pressure in the Gulf of Alaska to see if it persists. If it does, that would likely favor a drier-than-normal spring for planting. If the Alaskan low pressure doesn't persist, that would favor wetter-than-normal spring planting conditions in Iowa, as the wet month of March in Arkansas would indicate."
Summing up: Taylor says subsoil moisture is good in 80% or more of Iowa's fields this spring. Moisture reserves in the top 5 feet of soil are also good in Illinois, southern Minnesota and the eastern Corn Belt. The heart of the Corn Belt has good soil moisture and Indiana and Ohio are excessive because of the recent storms going up the Ohio River Valley.
Also, there's a weak El Nino occurring now. Although it is weak, the persistence counts. Thus, there's still a 70% chance the U.S. corn yield in 2015 will exceed the long-term trend. The trend is 162.3 bushels per acre this year, according to USDA.
For Elwynn Taylor's latest forecasts and weather commentary, you can follow him on Twitter at https://twitter.com/elwynntaylor, or Google search for "Elwynn Taylor talks 2015" on the Internet.