The week of May 19 through May 26 was slightly cooler than average in Iowa. Favorable field conditions allowed corn and soybean planting to catch up. "Planters were rolling across much of the state last week and as a result almost all of Iowa's corn and most of the soybeans for 2008 are now in the ground," notes Bill Northey, Iowa Secretary of Agriculture.
The weekly weather and crop condition survey released May 27 by Iowa Ag Statistics Service shows Iowa had 93% of its corn acres and 72% of its soybean acres planted by May 25. Normally by this date Iowa has 97% of its corn planted and 79% of the soybeans planted. Those "normal" numbers are based on the average of the past 5 years.
Corn is 54% emerged, versus 81% normal
Oat seeding for 2008 was 97% complete as of May 25, about 13 days behind last year, according to the weekly government survey. Oats emerged was 77%, which lags last year's 98% and the 5-year average of 99%. For soybeans, 12% of the state's acreage is emerged versus 36% normally by this time.
Corn is now 54% emerged, which is 8 days behind last year and 9 days behind the 5-year average. Normally 81% of the state's corn acreage is emerged at this time. Fertilizer application is 97% complete, 1% behind last year and 2% behind the 5-year average.
Pasture condition in Iowa rates 1% very poor, 5% poor, 26% fair, 56% good and 12% excellent. Cattle have moved to permanent pasture.
Poor corn emergence, runaway weeds
Iowa State University Extension crop specialists from across the state held their weekly telephone conference on May 27. They say the major agronomic issues for the week in many areas includes watching for soil crusting that is interfering with crop emergence--especially soybean emergence, however light rain can be helpful in alleviating that problem.
Additionally, getting runaway weeds under control in some fields is a developing issue. The focus on planting this spring has understandably taken precedence over some weed management activity, and it goes without saying that big weeds are tougher to control than little ones.
Corn fields have emerged across the state, and 5% to 10% of soybean fields can now be rowed, particularly in western and central Iowa, say ISU agronomists.
Soybean planting is progressing
"Statewide, Iowa is about three-fourths done with soybean planting," notes Mike Owen, an ISU Extension weed management specialist. "A lot of farmers have been planting corn and beans around the wet spots in fields. Soybeans haven't been in the ground as long as corn has this spring. Hopefully, beans won't have the emergence problems farmers have experienced in Iowa with corn. These small rains we've been getting recently, if they soften up the soil crust, the emergence should be improved and put the bean crop in good shape."
Weed control has been a struggle this spring. It's been wet and difficult to get in and spray. Pressed for time due to wet weather and planting delays, farmers have been dedicating their time to getting the crops planted, and many farmers decided to go ahead and plant their corn and beans and skip the preemergence herbicide application. They're relying totally on postemergence treatments for weed control in 2008.
"As a result we're seeing weeds now that are a lot larger than they ought to be and they're going to be extremely difficult to control," says Owen.
Will post herbicides control big weeds?
What will happen with fields where farmers are relying totally on postemergence weed control and wet weather continues in both corn and beans? "In many fields they have glyphosate-resistant corn and soybean varieties," notes Owen. "Glyphosate herbicide is an excellent tool to use to control emerged weeds. But the concern is with wet weather the weeds will continue to grow before you can get in and spray, and weeds will get too big for glyphosate to be applied on a timely basis and the glyphosate won't do a good job of weed control."
Application timing is absolutely critical. "Get into your fields and spray the herbicide when you can," advises Owen. "We don't recommend reducing the application rate of glyphosate per acre. You should be applying full rates in most of these situations. Of course, the rate you need to apply depends on the type of weed you are trying to control and size of those weeds. However, this year we're already seeing some of the winter annuals and weeds like marestail, giant ragweed, etc., getting pretty large. Cutting the application rate is not going to work for farmers in most cases. They need to get in and apply the full rate."