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Corn+Soybean Digest

Inoculation And Soybean Seeding Rates

Careful incorporation of inoculants, fungicide seed treatments and reduced seeding rates into a crop production program may give soybean farmers a boost in yield and extra money in their pockets at the end of the growing season.

A seven-year culmination of Ohio State University soybean inoculation evaluations consisting of 40 field trials and over 2,600 plots throughout the state have suggested that yearly seed inoculation can produce profits of 400-500%. A yield increase of one-third bushel per acre is profitable and, for many products, a 2-5 bu/acre increase is common.

An inoculant is a naturally occurring bacterium that maintains a symbiotic relationship with the soybean plant. The organism, which grows on the plant roots, converts nitrogen gas into nitrate, which the plant needs for growth.

"The soybean plant nourishes the bacterium and the bacterium helps the plant to grow," says Jim Beuerlein, an Ohio State agronomist. "It's a pretty unique relationship and can be profitable for the farmer."

The 2001 soybean inoculation trials evaluated 14 different products at six sites and showed an average yield increase of over 6.5%. Profit generated ranged anywhere between $5-12/acre.

Improving a crop's health through the use of fungicide seed treatment is another way a farmer can increase profits.

"Farmers need to pay special attention to the diseases they have in their fields and then choose a fungicide package to control diseases for the varieties that may not be resistant to them," says Beuerlein.

Phytophthora, Pythium and Rhizoctonia are three root rot diseases that can cause major crop losses if not adequately controlled.

"Proper variety selection and proper seed treatment can eliminate those diseases as a potential problem," says Beuerlein. Adding fungicide treatment to the inoculated seeds generated additional profits as high as $15/acre. Results of the inoculation and fungicide performance trials are located at

Another way a farmer can save money is to reduce the seeding rate. An Ohio State seeding rate study conducted in 2001 indicated that reducing the seeding rate by 50,000 seeds/acre could potentially save a farmer up to $10/acre. Study results showed that maximum soybean yields were produced with seeding rates ranging between 150,000-175,000 seeds/acre.

"Farmers tend to plant 25% more seed than they need to. Some of that is to compensate for poor equipment or lack of calibration. Some of it is just habit, but some producers feel that the high seeding rates are needed for better weed control," says Beuerlein. "Most people can reduce seeding rate by 25% without affecting either weed control or yield and therefore increase profits."

Beuerlein says that proper calibration of equipment to achieve the desired number of seeds planted per acre, or the number of seeds per foot of row, is a very important step in reducing production cost.

For more information on calculating soybean seeding rate, log onto

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