Plant Soybeans Early
With the wet weather we have been having, you probably think you will be lucky if soybeans are planted by the middle of May. Research shows you may want to consider planting soybeans earlier, before you are done planting corn. Research funded by the Nebraska Soybean Board and conducted at the University of Nebraska-Lincoln (UNL) indicates soybean yields decrease when planting is delayed after May 1st. This research was conducted at the research farm at UNL’s East Campus in 2003 and 2004. Results of this study show a yield decline can range from (0.25) bu/ac to (0.625) bu/ac for each day planting is delayed after May 1st.
In terms of production and economics, if soybean planting is delayed to May 20th, soybean yields could decline as little as 5 bu/ac (20 x 0.25) or as much as 12.5 bu/ac (20 x 0.625). At today’s soybean prices ($12.00/bu) this is a potential loss of $60.00 - $150.00 per acre in gross revenue. Dr. James Specht, who conducted this research, indicated that soybean plants add one main stem node every 3.7 days after the first trifoliate appears until seed development begins. The node is where the flowers, then pods and seeds in those pods are produced. As a producer, you want enough seasonal time to produce as many main stem nodes as possible. For soybeans planted on May 20th, your crop could potentially lose 5 less nodes on the main stem, which is a significant number of soybeans.
The benefit of earlier planted soybeans is they collect as much sunlight as they can during the growing season, which translates into potentially more soybeans and higher yields. The canopy closes earlier so rather than having sunlight fall on the ground, it is intercepted by the leaves. This also reduces the amount of soil water loss by evaporation so it goes to the soybeans. These factors all contribute to higher yield potential.
There are other environmental factors that also influence soybean yields, such as insects, diseases and rainfall. Early planted soybeans will be susceptible to bean leaf beetles that have over wintered, especially if they are the first soybeans planted in the area. Heat and drought stress can also have a major impact on soybean yields and could influence earlier planted more than late planted soybeans. As you begin planting corn, you may also want to consider planting soybeans around May 1st as part of your planting strategy if you are not doing this already. Much of this information is from the April 4, 2008 issue of CropWatch. For the whole article and photos of different planting dates go to: http://cropwatch.unl.edu/archives/2008/crop5/soybean_planting.htm. If you have questions about this article or other issues in agronomy, feel free to contact me at the Nemaha County Extension office at the courthouse in Auburn (402) 274-4755.
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