Iowa State University Extension soybean agronomist Palle Pedersen notes that soils are already saturated in Iowa, and farmers may be planting into wetter-than- normal conditions this spring. You may be able to improve yield potential this year by planting bean seed that is treated with a fungicide, he says.
"That's one of several key considerations farmers need to be thinking about before they go to the field this spring," says Pedersen.
Be careful with seedbed preparation. Soil is already very wet. "We will have plenty of moisture," he says. "When you plant into a wet seedbed, you can get sidewall compaction and also seedling disease and germination issues."
Fungicide adds protection in wet soil
"This is a year to think about protecting soybeans with seed treatment, not only because of wet soils but also because we don't have the best seed quality in many cases this year. Fungicide seed treatment can protect the seed in a spring like this," says Pedersen.
Fungicide seed treatment in most cases will not increase yield—if you get your desired stand. But it will protect the stand, to help you get the desired plant population so you don't have to go out and replant, he adds. That is a key consideration in a wet spring.
What about using an insecticide treatment on seed to protect against bean leaf beetles this spring? "We've done considerable research on bean leaf beetles and insecticide seed treatment and we know it doesn't take a lot of beetles before you can get your money back by using an insecticide treatment on the seed," says Pedersen. "An important question is: Will bean leaf beetles be a problem this spring? Our ISU entomologists don't know yet about how many bean leaf beetles have survived the winter. It's been very cold this winter but we also had a lot of snow to help protect the overwintering population of bean leaf beetles."
Choosing a fungicide seed treatment
For sure, a fungicide seed treatment is something farmers should think about using, he says. If these wet soil conditions continue and you plant beans into wet soil, the fungicide seed treatment will help protect the seed.
Most of the seed treatments available are not very systemic, but a few of them are. However, even a nonsystemic fungicide will protect seeds when they are sitting in the ground and until they emerge. If you don't have the best seed quality, that fungicide treatment on the seed may be able to help you get a good enough, uniform stand, says Pedersen.
"Then you won't have to replant," he notes. "I think it could be worthwhile to use a fungicide seed treatment this year, especially to avoid having to replant. First of all, it could be that you can't get the seed you want for replanting. But also, when you replant you delay the crop. By delaying planting by two to four weeks, the yield potential drops. That's a consideration--can you afford to replant if it will drop your yield potential? Also, replanting is going to increase your cost of production. You'll have to buy more seed."
Best time to plant soybeans?
When is the ideal time to get out and work your field and get some soybeans planted? The key phrase is: "Work the field." When you have wet soil conditions early in spring and work that ground too early you'll create bad, cloddy seedbeds and soil compaction.
"Based on our ISU research in recent years, we say farmers should not start planting beans before April 25 in the southern two-thirds of Iowa, and May 1 for the northern one third of Iowa," says Pedersen. "Looking at soil conditions currently across the state, I don't think planting too early is going to be a problem this year. Farmers won't likely have to worry about planting beans too early this spring because they are not going to be able to get out there before these dates."
But when you are finally able to get into the field, be sure when you start planting that you don't mud-in the beans. "Last year was a good example," says Pedersen. "We don't have data to support this, but my gut feeling is the high level of Sudden Death Syndrome disease in soybeans in Iowa last year, a lot of that was related to poor seedbed conditions. A good share of Iowa's soybean acres in 2007 were "mudded-in" as seeds were planted in wet soils, and in addition, the crop went on to receive very heavy rainfall in August."
You want to avoid having to replant
You can make trouble by planting into soils that are too wet, creating problems the crop has to live with all season long, and the effects will show up as a disappointing yield at harvest.
"We don't have a shortage of soybean seed," adds Pedersen. "If we have to replant, there may be enough seed out there but we may not be able to get what we want and what we need. So every effort should be put into that first planting to make sure it's the only planting."
There are some issues with lower-than-normal seed quality this year. Pedersen has talked to a number of people this winter about soybean seed quality problems and lower-than-normal germination tests on some of the seed harvested last fall. In recent weeks, he's talked to more seed companies and this problem looks like it may be worse than first thought.
Most seed industry people this past winter thought Iowa would be okay, because most of the seed that was having problems with lower-than-normal seed quality was in maturity groups planted in areas south of Iowa. "But we are now finding test results showing some soybean seed in Iowa testing only 85% or less germination," he says. "I've heard as low as 70% for some seed. Be extremely careful this spring with the seeding rate you plant. You may need to adjust the number of seeds you plant per acre, depending on what the germination test shows on the seed bag's tag."