Weather issues topic of discussion a Northwest Research Farm field day
By By Nancy Vander Schaaf
nanrvs@gmail.com
Date Modified: 07/29/2010 9:47 AM
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CALUMET, Iowa — The recent field day at Iowa State University's Northwest Research Farm near Calumet included a farm tour and discussions on timely crop topics.
"Evaluate what your corn is doing, and what its symptoms are," says Joel DeJong, ISU field agronomist.
DeJong showed his audience what to look for in cornfields including seed depth, compaction and rootworm damage.
"I want corn at 1 1/2 inch to 2 inches," said DeJong.
Otherwise, the nodal root system will be shallow. When planting, he advises going across the whole width of the planter to make sure a unit isn't planting too shallow.
He peeled roots back to show the effects of sidewall compaction.
"The best time to check for rootworm damage is the middle of July," said DeJong. "Then they'll be close to pupating, and the roots will not have regrown yet to hide the damage. You should be out there in your fields."
"Take your spade in your soybean fields, too," he said. "Look for nodulation and look for cysts."
With the recent wet weather there could be more disease risk in soybeans, said DeJong. Fusarium and phytophthora are concerns in flooded areas.
He showed the audience brown spot and bacterial blight on beans.
"No-till beans had less soil to splash, so they have less bacterial blight," said DeJong.
Erin Hodgson, ISU Extension entomologist, spoke about aphid management.
"So far in 2010, soybean aphid has been detected at very low levels in northern Iowa," Hodgson said.
She recommends scouting fields weekly.
"The threshold is 250 aphids per plant on 80 percent of plants and populations increasing," said Hodgson.
Extensive research has been conducted at the Northwest Iowa Experimental Farm regarding phosphorus and potassium placement.
"This is our 16th year of research," saids Antonio Mallarino, ISU Extension soil fertility and nutrient management specialist, who gave an update on P and K placement. "The placement method of phosphorus does not matter. For potassium, we recommend deep placement with ridge-till. We recommend deep banding for no-till. However, you will not see the benefits every year."
When he began his research, he had expected to find stratification of phosphorus near the surface. Due to the expense, they had initially considered dropping potassium from the research, but they ended up finding a response to potassium placement and not to phosphorus placement.
"You need to adjust to yields on your farm," said Mallarino. "There are still people out there applying the same rate as they did 22 years ago. They need to wake up. If you remove more, you need to apply more."