What are the major problems you'll have if you plant corn in soil that is too wet and too cold? "If you plant corn when soil conditions aren't good, you have to live with those mistakes all year," notes Roger Elmore, Iowa State University extension corn agronomist.
It's hard to get the seed established well, and you create soil compaction. Certainly, sidewall compaction is a big problem. "The roots don't grow out across the row as well, especially early in the growing season," he says. "That limits water and nutrient uptake."
It also inhibits the ability of the plant to stand well over the whole season. Unless we have a growing season with plenty of rainfall, the plant will have problems because those roots don't develop as well and don't go down as deep as they should."
How deep to plant corn?
Elmore has received questions from farmers this spring about planting depth for corn. Is it wise to reduce the depth, plant shallower than normal, if you're planting corn early? "One thing not to do is to plant shallower than normal when it is cold and wet like this," he says. "That's one of the worst things you can do. I'd put the corn in the ground about 1.5 to 2 inches deep, that's where I normally plant."
He cautions people against doing the damage when they decide to plant in conditions not favorable to getting a good seedbed. Soil temperatures come along once soil conditions are right for planting. Corn can be planted in Iowa anytime after April 15 that the soil is ready. The best date to start planting soybeans is around April 25 - if soils allow.
During the 2008-crop season, every Monday ISU Extension agronomists at Ames will hold a telephone conference with ISU Extension field agronomists across the state to get an update on current crop problems and concerns. The first weekly phone conference was last Monday.
Weeds and insects developing
ISU Extension field agronomists across the state don't see big problems with winterkill of alfalfa as the crop starts to green up this spring. But it will soon be time to start watching the crop for the presence of alfalfa weevil.
The ISU agronomists also talked about bean leaf beetle. Will this pest be a problem in soybeans this year? It's hard to say, but they sense that there will be areas of the state that will have infestations of this pest this year.
"The one thing we can be sure of is that weeds are coming up and beginning to grow in fields," says ISU Extension weed management specialist Mike Owen. "In the southern half of the state, the winter annuals are already out there. Even though you may not be able to see them from the road as you drive by your fields, they are there. If you are planting corn, you'd better be taking care of those annual weeds and there will be plenty of annual weeds, too."
Will killing frost hit in May?
ISU climatologist Elwynn Taylor says it's not very often that you expect to have a killing frost in May. That's why the ideal planting dates are in late April or early May.
He says 28 degrees F is the killing point for corn. When the thermometer drops to 28 or below, the cold temperature will kill the leaves of the corn plant first because the growing point is still underground. "Such cold temperatures will kill soybean plants if we have 28 degrees or below--if that low of a temperature touches the plant for more than a minute or two," he says. For example, if the temperature drops below 28 degrees overnight.
"So it's a definite danger. This year we can't say a late frost is a greater danger than usual. But we expect to have alternating cold and warm outbreaks," adds Taylor.
La Nina weather pattern to continue
La Nina is a weather event that encourages this type of weather. "We have mild weather when there is an El Nino going on," says Taylor. "We usually don't have record cold or record heat when there is an El Nino going on. But we often get both extremes of cold and hot when we have a La Nina going on. The La Nina is still going on currently, although it is weakening. But it is not in neutral territory yet, it is still moderately strong."
The latest forecast from the National Weather Service shows none of the 18 different scientific groups on their panel that makes calculations now expects the forecast to change to an El Nino this growing season. Half of the experts expect it to stay as a mild La Nina, and the other half expect it to be in neutral territory, but on the La Nina side.
Expect 2008 corn yields below trend
Either way, the current situation of widely fluctuating weather says the conditions are open for the weather to be extreme this year, says Taylor.
As he has explained in meetings this winter, Taylor still expects U.S. corn yield to be below the long-term trend this year. "At the moment, the preponderance of indicators are for below trend line yields in 2008," he says. "I think you should plan on prices that are a little better prices for corn and soybeans that you might have been thinking for the end of the season."