Soybeans: Plant Early or Plant Late?

Dan Davidson, Agronomist PhD, CCA

What does planting date mean to your soybean yield? Soybeans planted early can benefit more than early planted corn.

There has been a trend to planting both corn and soybeans early. As a kid growing up in Northeast Nebraska in the ’60s and ’70s, I recall that April was for tillage and sowing oats, May was for planting, and June was for weed control and haying. By 2000 we all knew that we could plant corn in April, and once corn was planted, soybean planting started immediately.

How things have change since 2000! Farms got bigger with more acres to plant, and growers started pushing planting earlier to the beginning of the crop insurance window, and even earlier on some acres. And seed treatments got better and become more commonplace. Corn seed has been treated for decades and now upwards of 90% of soybean seed is treated. We all began to realize that if the soil is fit and there is a good window of weather ahead, we can push the planting envelope even sooner.

Soybeans can be planted early, and as early as corn – something we have discovered the last few years and now everyone is promoting. Long-term research carried out by Emerson Nafziger at the University of Illinois shows that shows yield is at its highest when planting is in April. It begins to decline by May 1 and continues to decline through May and June. A June 20 planting date, which corresponds with double cropped soybean planting, shows a 25% reduction in yield.


Illinois Planting Date Studies, Emerson Nafziger, University of Illinois.

The practice has been to plant corn first and then plant soybeans. But that’s changing with farmers acquiring two planters and beginning to plant corn and soybeans at the same time. And savvy farmers are beginning to recognize that you can plant soybeans, but not corn, when the weather window is closing in. Corn seed sitting in the soil and waiting to germinate can’t tolerate a cold drink of water, while soybean seed – with its high oil content – can. If a storm is coming with cold weather and rain, and you want to get a few more acres planted, switch to soybeans.

But more recently we have realized that soybean yield can benefit more from earlier planting than corn. If you plant corn in the window from April 15 to May 5 into fit soil with normal weather conditions, yield potential is about the same, and late-planting yield penalties don’t begin to accumulate until after May 10. However, soybeans planted early build a bigger plant by summer solstice with more nodes, potential pod-bearing sites and canopy to support it, which improves potential yield at the end of the season. Though August rains will still have the final say!

Fortalis® is an essential crop input

Your soybean yields can also benefit from Fortalis®, an advanced crop enhancement foliar spray that works by mobilizing calcium already existing within plant tissues, resulting in higher pod retention. When applied as a tank mix, Fortalis® with a fungicide or insecticide contributes to better plant health and higher yield potential. It’s an essential crop input that you need to get the most out of your crop.

Dan Davidson is a PhD agronomist, part-time farmer and soybean expert from Nebraska who consults with soybean checkoff and industry on crop production, marketing, and product development projects.



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