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Four steps to boosting your soybean yield

The first thing to know about maximizing soybean yields is that the two biggest profit makers are planting date and row spacing. That probably doesn't surprise many farmers. But there are a few facts to keep in mind in thinking about how to increase yields and profits.

Ohio State University Extension agronomist Jim Beuerlein shared the following facts in a recent edition of the C.O.R.N. Newsletter:

Yield potential starts to decrease in early May most years and by late May is just over a half bushel per acre per day.

A five day delay in planting the last week of May will reduce income by $30 per acre if soybean is worth $10 per bushel.

Switching to narrow rows will also increase yield and profit. On light colored soil, the row spacing should be as narrow as possible regardless of planting date. On dark colored soil, row spacings should no wider than 15 inches in May and as narrow as possible for June plantings. Yield increases about one-third bushel per acre as the row spacing is decreased from 30 inches to 7 inches.

What if you are already planting early in narrow rows? Beuerlein says there are two other very profitable practices: fungicide seed treatments and inoculation.

Fungicide seed treatments will ward off infection of the root rot diseases for two to three weeks allowing plants to get a head start on diseases and be better able to ward off the yield loss caused by disease.

He says that over time, the use of fungicide seed treatments in Ohio will increase yield three to eight bushels per acre depending on soil drainage, crop rotation, variety selection, and other factors.

The results of a 2003 fungicide seed treatment study Beuerlein conducted in Ohio are available here:

He says the take home message from the study is that fungicide seed treatments are very effective tools for improving plant stands and root system health. "Seed treatment fungicides should always be used on soybeans, regardless of variety, crop rotation, soil type, planting date, or tillage," he says.

As for inoculation, he says most producers can expect yield increases of three to eight bushels per acre depending on soil characteristics and yield potential. Results of Beuerlein's 2004 Ohio Soybean Inoculation Study are available here:

He says ten years of soybean inoculation evaluation consisting of 66 field trials and over 7000 research plots indicate that inoculating soybeans is a very profitable practice. The average yield increase over ten years has returned a profit of over 300 percent. For most inoculation products, a yield increase of half a bushel per acre is profitable and yield increases of 2 to 7 bu/acre have been common. Since 1995 the inoculation of soybean seed in Ohio has increased from a few thousand acres to over two million acres. The primary reason for the rapid increase in use of inoculation materials is that over time their use has been profitable.

When applying a fungicide or using fungicide treated seed, be sure the fungicide has dried before applying inoculation material to the seed. Inoculation products may be mixed with some fungicides and applied to the seed together. Be sure to check labels for compatibility. Work is underway to develop formulations of fungicides that can be premixed with inoculation materials and applied together.

More inoculation advice

Palle Pederson from ISU offers an information sheet about inoculation with advice about how to know whether you need to inoculate your fields. It includes the results of inoculation trials in Iowa. The Iowa researchers' conclusion is this:


"The decision on whether or not to inoculate is still dependent on whether the site has a recent history of healthy-looking soybeans. Iowa has a good population of B. japonicum in most soils, if soybean has been grown in recent years in the field. Because most cultivated fields include a rotation with soybean, the need to inoculate with more bacteria rarely exists. The practice of inoculating fields that have been out of soybeans for more than three to five years may still be a good insurance practice due to the inexpensive nature of the inoculant. Last year's data was inconclusive as to whether any of the new inoculants will consistently provide a higher yield in a corn-soybean rotation. More than a single year of data is needed before we can draw any final conclusions. The evaluation of soybean seed inoculants will therefore continue in 2005."

Pederson's current recommendations for Iowa are to inoculate the seed if:

The field has never been planted to soybean.

Soybeans have not been grown in the field in the past three to five years.

The soil pH is below 6.0.

The soil has a high sand content.

The field has been flooded for more than a week, creating anaerobic conditions.

See the results of the Iowa inoculation trials:

The first thing to know about maximizing soybean yields is that the two biggest profit makers are planting date and row spacing. That probably doesn't surprise many farmers. But there are a few facts to keep in mind in thinking about how to increase yields and profits.

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