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Sink stressors with the seed

If you're looking to boost soybean yields, there's an easy way to do it. Plant early.

Iowa State University (ISU) research shows early planting can spike yields. If soils are fit, the optimum time to plant in central and southern Iowa is the last week of April. In northern Iowa, farmers may begin planting the first week of May. In ISU tests, yields slipped .40 to .90 bushels per acre per day for each day following these dates.

The downside is that early planting means farmers face wetter and colder soils. They aid diseases like pythium and rhizoctonia to thrive. Ditto for early-season insects like wireworms and seed corn maggots.

The good news is there's a way to deal with it. Seed treated with fungicides and/or insecticides can thwart such stressors.

"On soybeans, we've used a fungicide seed treatment for varieties we plant in late April or early May," says Andy Hortenstine, who farms with his brothers, Mark and Jake, near Ramsey, Illinois. "It's usually wetter when we start planting them, so we treat about half to three quarters of our beans."

Seed treatments also help ensure each seed you plant makes it to harvest. That's particularly important in light of rising seed costs that have prompted farmers to slice soybean seeding rates. From 2000 to 2006, U.S. farmers sliced seeding rates 9.2% on average, says Mark Jirak, crop manager for Syngenta.

"What you put in the ground, you want to come out of the ground," says Palle Pedersen, ISU Extension agronomist.

Seed treatments can also help you make every planting minute count. As farm size increases, timely planting is more important. That's particularly true for larger growers who have many acres to cover.

"They can't afford to spend time with replants," says Jeff Daniels, seed treatment specialist for Bayer CropScience.

There's a catch, though. Seed treatments add cost. Fungicide treatment costs revolve around $3.50, while insecticide and fungicide seed treatments typically cost between $10 and $14 per acre.

They don't always boost yields, either. Four years of University of Minnesota (U of M) fungicide trials at 28 data points showed significant yield spikes just six times.

"It is likely that the short active period for these fungicides, up to 14 days, is too short for very slow emerging soybean crops," says Seth Naeve, U of M Extension agronomist.

Thirteen ISU tests from 2005 to 2007 showed plant populations did increase an average 4,000 and 13,000 more plants per acre using a fungicide and a fungicide/insecticide seed treatment.

However, fungicide seed treatments didn't raise yields in the tests. Pedersen says as long as growers are able to achieve a uniform harvest stand of 100,000 plants per acre, fungicide seed treatments rarely raise yields.

It was a different story with the fungicide/insecticide combo, which boosted yields 3.6 bushels per acre on average above check tests.

"All of it was driven by bean leaf beetles," says Pedersen. The insecticide protected the seed from the overwintering generation of bean leaf beetles.

If you're looking to boost soybean yields, there's an easy way to do it. Plant early.

Besides controlling early-season insects, insecticide seed treatments provide some soybean aphid protection. Bayer CropScience officials say its seed insecticide, Gaucho, provides up to 65 days worth of soybean aphid protection.

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