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THE TRADITIONAL “Corn is King” mindset has most farmers in the Midwest prioritizing corn planting in the spring and treating soybeans as a secondary crop. But switching the order can offer benefits such as higher yields, spreading out the workload in the spring and an improved opportunity to get cover crops established in the fall.
Planting date studies conducted by the University of Illinois from 2007 to 2018 looked at yields of both corn and soybeans planted on five dates between April 10 and May 30.
The results showed soybean yields were highest with the April 10 planting and began to decline with each successive date, concluding with a 15.8% drop by the end of May. Corn also showed a drop in yields, but it started later and was more gradual, showing only a 13.4% decline with the final planting (see Figure 1).
EARLY DOES IT. Research from the University of Illinois showed that soybean yields began declining with each successive planting after April 10, ultimately falling by 15.8% with the May 30 planting date. Corn had a more gradual decline beginning after April 20 and falling by 13.4% with the May 30 planting.
Studies by Michigan State University, on the other hand, have shown that soybeans had no yield decrease if planted by May 1, but after that yields declined, according to Manni Singh. “There’s about a half a bushel decline in yield for each planting after May 1,” says…