Soybean seeding rates

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included

Recent research conducted in the North Central Corn Belt suggests that soybean planting populations may be able to be dialed back somewhat without compromising yield, or more importantly, profitability. Research conducted throughout the Midwest is showing that a final harvest population of 100,000 plants per acre is generally sufficient to achieve maximum yield. The challenge is in deciding what your seeding rate must be in order to achieve a final harvest population of 100,000 plants or higher.

What does this mean for Michigan soybean growers? With tighter profit margins expected for most crops in 2009 including soybeans, growers do not want to compromise yield. However, as mentioned above, recent Midwest studies clearly show that it is not necessary to continually increase soybean planting populations in order to obtain maximum yield. Unlike corn, soybean has a great propensity to compensate or flex when plant populations vary. Therefore, the optimal planting population range is wider for soybean than it is for corn. Determining the minimal scale of that optimal soybean planting population range will optimize profitability and still maintain yield. As a starting point, begin with a planting population of 175,000 seeds per acre for drilled systems and 130,000 seeds per acre for 30-inch rows and then adjust from there based upon field productivity and planting conditions. Low productivity fields require higher seeding rates to obtain maximum yield than do high productivity fields. Similarly, if forced to plant in less than optimal soil and planting conditions, adjust seeding rates upward to compensate for expected decreases in seedling emergence and survival.

Several things to consider when operating on the low end of the optimum planting population range include, managing in a manner that maximizes emergence and seedling survival. Calibrate your drill or planter to ensure that seed drop is adequate and uniform across all rows. This is important to do every year as seed size and planter mechanical efficiency and wear can vary from year-to-year. Avoid planting when soil conditions are less than optimal to facilitate good seed to soil contact and seedling germination. Inoculate soybean seed with Rhizobium bacteria regardless of field history. Finally, if planting early in the season, consider using fungicide-treated seed (Be sure it is labeled for use with your soybean inoculant.) to protect against soil borne root diseases.

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