New Soybean Seeding Rate Recommendations in Iowa

Palle Pedersen, Faculty, Agronomy


There are two ways to improve soybean growers bottom line either by increasing yields or decreasing production costs. Yield is of greatest interest because much of the production cost is fixed (land and equipment) and cannot be easily changed. Soybean production costs on the other hand have continued to rise due to improved technologies. Based on this situation a large project was initiated in 2003 to identify how we can cut our production costs without losing profitability. The previous soybean seeding rates were challenged. Prior to the development of glyphosate tolerant soybean, plant populations were often used as a tool to manage weeds. That is not necessary anymore since we have improved our post-emergence weed management programs. Soybean plant can compensate for space and yield doesnt correlate with plant population as long as a minimum number of plants have been reached, which is 100,000 plants per acre. The growers will therefore be able to cut their seeding rate without losing productivity as long as they manage the weeds properly.


The objective of the educational effort was to provide awareness that the soybean plant can compensate for space.


A major educational effort was implemented by ISU Extension through the soybean extension and research program in the Department of Agronomy to increase the awareness of Iowa farmers and agribusiness personnel of the issues related to soybean seeding rate recommendations and how it can help growers to increase their profitability. During this time, I had hundreds of phone calls on soybean seeding rates, one television interview, 14 radio interviews, dozens of interviews with reporters from newspapers or farm magazines, and 39 presentations with a total of 4,600 attendees.   


As a result of extensive information deliveries from the soybean extension and research program at ISU, many soybean farmers went to meetings and evaluated information from our research across the state. The economic impact is astounding. Based on just 3 years of data our results were so consistent that a new recommendation for seeding rate was proposed to the growers in January 2006 that will save the Iowa farmer approximately 55 million dollars each year. Without this information from ISU extension growers would have continued to use the old seeding recommendations that are too high today despite using new technologies, such as the glyphosate tolerant seeds.

September 2006

142 Integrated Pest and Crop Management

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