Reviewing the 2015 growing year
By LARRY KERSHNER
KANAWHA – After watching row crops struggle with stem canker and sudden death syndrome in soybeans, and northern corn leaf blight in corn, reviewing the 2015 growing season and a chance for insights planning 2016 attracted about 50 area farmers Sept. 3 to a field day in Kanawha.
Iowa State University Extension hosted the event at its Northern Research Farm, just south of Kanawha.
The event included four stops – an overview of soybeans, corn, a look at cover crops, and fall fertilizer applications.
Matthew Schnabel, farm superintendent, updated his audience that crops were 200 growing degree days behind the five-year average as of Sept. 3, while enduring 24 inches of rain this season, with August being the wettest month so far.
“But I expect with warmer weather coming, they (growing degree days) will catch up a little,” Schnabel said.
Daren Mueller, an ISU Extension plant pathologist, said the recent rise in sudden death syndrome is a result of the predominant corn and soybean rotation.
“We kind of selected for it,” Mueller said, “through this rotation.”
He continued saying that each time seed genetics or land practices are tweaked, “We’ll see something else happen.”
As an example, he said the switch to planting narrow-row soybeans as a weed control practice, can lead to more white mold in soybeans during cool, wet growing seasons.
When seeing yellowing in soybeans, he cautioned farmers to be sure what they are seeing.
“It could be SDS,” he said, “or it could be white mold, iron chlorosis, stem canker, or potassium deficiency.
“And if you are trying a new fungicide, start small. Sometimes a product can be the best choice, and sometimes it could be the worst.”
Stem canker, Mueller said, has made its reappearance in Iowa, and is the most common soybean disease in Indiana.
He said the symptoms look like brown stem rot, causes early death in plants and generally leaf-yellowing is seem in the lower canopy.
When planning to manage against SDS, Mueller reminded farmers they cannot defeat the pathogen just by planting corn the next year.
“It’ll still be there for the next bean year,” he said.
In the northern half of Iowa, northern corn leaf blight has been prevalent, said Paul Kassel, an ISU Extension agronomist.
And recently, some corn fields have shown to be dying from the top down, while the lower plant goes into natural firing from below.
That top-of-the-plant disease, he said, appears to be anthracnose top die back. That can be determined by pulling the tassel and examining the end that comes from the stalk.
A pinkish, glutinous appearance is the tell-tale sign of anthracnose.
Concerning NCLB, the break out in North Iowa came later in the season, which may have minimal effect on grain quality.
“If it shows up during pollination,” Kassel said, “it threatens grain quality.”
The fungus’ spores eat plant tissue and prevent the plant from filling the ear properly, he said.
Mueller said that each square-inch NCLB spot on a leaf, contains hundreds of thousands of spores.
If the lesions appear in the upper leaves, the infection came from a neighboring field.
If on lower leaves, the infection came from neighboring plants.
Kassel said it’s difficult to decide if a farmer should spray for NCLB since it is easily thwarted by dry, warm weather.
In addition, the efficacy of an early applications of fungicide can be questionable, Mueller said, because other factors will effect the fungicide’s mode of action including hybrid, application rate and plant population.
Farmers had a chance to wander through and pull plants from a cover crop demonstration plot, designed to show how well they grow and cover soil.
Angie Reick-Hinz, an ISU Extension agronomist, said cover crops are a major part of the practices recommended for keeping nitrate and phosphorus in fields and out of surface waters.
“We think that if we had cover crops on all row-cropped fields,” Reick-Hinz said, “Iowa could reduce nitrate (escapes through tile lines) by 31 percent.”
She said cover crops will take up and sequester nitrogen during the seven months fields lie otherwise bare between harvest and planting.
They also add organic material, increases the carbon and nitrogen pool in the field, and provide a more stable nitrogen source in the soil.
They also slow or stop surface water and wind erosion; while suppressing weeds and providing extra forage options for livestock.
Dean Stromer, of Klemme, examined a radish tap root. He said he uses strip-till practices on his farm and thinks cover crops are a good between-seasons practice.
“Anytime you can grow something to control water and wind erosion is good,” he said. ‘The challenge in North Iowa is being able to get it established early enough to make a difference.”
Dr. Antonio Mallarino, an ISU Extension soil fertility specialist, provided a reminder for farmers to have their fields soil tested.
He said in times of low market commodities the temptation is to cut on inputs.
“But don’t cut across-the-board,” he said. “Cut where (nutrients) are high or very high, but don’t cut where it’s low or very low.”
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