Sun and warm temperatures this past week continued to boost Iowa's corn and soybean crops. Even though crop growth is stronger, corn plants are uneven in fields that were flooded and saturated with too much rain last month.
That's the message delivered by the weekly crop and weather report issued July 14 by Iowa Ag Statistics Service, the Iowa office of USDA's National Ag Statistics Service.
Corn is shorter than normal
Corn averaged 49 inches tall, 22 inches behind last year at this time and 17 inches behind the 5-year average. Both corn and soybean conditions are rated 58% good or excellent as of July 14. The previous week they were 57% good or excellent.
The report shows 35% of the state's soybean plants are blooming, 29% behind a year ago and 19% behind the 5-year average.
The first cutting of alfalfa is nearly complete at 97%. The second cutting is 16% complete--39% behind the 5-year average. Hay conditions are 63% good or excellent, 3% ahead of last week. Pastures are 68% good or excellent.
Iowa corn starting to tassel
Crops are looking better across the state, say Iowa State University agronomists and field staff who hold a telephone conference on crop conditions each Monday.
"At mid-summer, Iowa is actually doing ok with the corn and soybeans that survived all the weather problems the state had earlier this season," says Mike Owen, ISU Extension weed specialist at Ames who coordinates the weekly phone conference. "What kind of yields we get from corn and soybeans in 2008 still depends on what happens the rest of the growing season. But corn in particular has picked up a lot of color and some fields in Iowa have begun to tassel."
ISU Extension corn agronomist Roger Elmore predicts that in the next 7 to 10 days most of the state will have corn that's tasseling, which is good. "If the weather cooperates, we'll be okay," he says. "The nitrogen situation is questionable, as the heavy amount of rain we received across much of Iowa earlier this summer leached a lot of the nitrogen away. If we run out of nitrogen that's not a good thing. It could limit yield potential."
An early frost this fall?
The big issue is when will it frost this fall? "If the first killing frost comes early, then we'll have some problems. And if we have a late, very dry type of fall, we may not be as bad off with this year's crop as we once thought," says Elmore.
Elmore has looked at silking date and what could happen with corn yields. You add about 60 days to the silking date and that gives you the date when your corn will reach physiological maturity—which is when it is safe from frost.
If the corn starts silking on July 18 that would mean the maturity date is October 23 and we'll get about 96% of our yield potential—which would be good.
The silking date this year is going to vary because much of the crop was planted late. "One of the problems we have right now as we look at corn on corn is it is very uneven in it's growth, as compared to corn that follows soybeans in rotation," says Elmore. "The unevenness of that corn is going to affect silking date and pollination date."
So, looking across the state, if the corn in some fields starts to silk later, maturity dates are going to change a little bit and yield potential is going to go down.
Soybean crop also looks better
How about soybeans—how do they look now? "They are looking better," says Owen. "We are seeing some iron chlorosis starting to show up on soybean plants in northern Iowa, which is probably normal. Reports are it's not as bad as it's been in past years."
Also, foliar soybean diseases are starting to show up. But overall, the beans are growing. "One bit of good news this week is that soybean aphid populations are low this year," says Owen. "This year they seem to be down around the levels they were in 2004 which is the lowest population of this pest that we've had. So far, 2008 is tracking like a 2004 year for soybean aphid—so that's a good sign."
The potential downside is that since planting was late this year and soybeans are a photo-sensitive plant, when the day-length gets to be a certain time the bean plants start to flower. "So what we are generally seeing is a lot of Iowa's soybeans this year are now setting pods a little lower than normal on the plant. That'll make it interesting when farmers harvest the beans this fall," notes Owen.