Soybean planting date considerations
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EmailConsistently higher yields have been achieved when planting soybeans earlier from mid-April to early-May, but certain risks with early planting need to be considered.
Much work has already been done to prepare for a successful soybean production season—seed dealers have been consulted and varieties/maturities/traits selected, fertilizers purchased and applications planned or made, crop protection chemicals purchased, planters maintained and many other steps. As we head into planting season, another set of management decisions needs to be made—tillage, planting date, seeding rate, possibly seed treatment application, fertilizer or other growth-promoting products applied with the planter, etc.
Various MSU specialists and educators have conducted research funded by the Michigan Soybean Committee (MSC) over the years to help with these decisions, and a quick search on the MSU Extension website and the MSC website will help you access those results. The Science for Success team of soybean specialists from around the country have identified planting date as one of the most important factors affecting soybean yield. This article will focus on planting date with MSC-funded research results from three sources: MSU’s cropping systems agronomist Manni Singh; Missy Bauer of B&M Crop Consulting; and the Michigan Soybean On-Farm\Research program.
In 2023, researchers with the Boots on the Ground benchmarking project, funded by the North Central Soybean Research Program (NCSRP), worked with USDA’s Risk Management Agency (RMA) to adjust the earliest soybean planting dates in many regions, including Michigan. Now most Michigan soybean farmers are able to plant as early as April 20 or 25, depending on location, and still opt for federal crop insurance (Fig. 1). The researchers found a 2–3 bu/ac decrease in yield potential occurs in Michigan with every week of planting delay past around April 25. Singh’s small-plot research has produced similar results with a smaller penalty found earlier in the season and increasing later in May (Fig. 2).
On-farm research results have shown the same trend of higher yields with earlier planting. Singh found 16 of 34 sites from 2019–2021 had significantly higher yields with earlier planting (roughly three weeks) and only two sites with significantly lower yields (Fig. 3).
Bauer found a 4.6 bu/ac advantage on average when planting in late April-early May compared with planting after May 15 from 2017–2019 with no sites having significantly lower yields with the earlier planting. In a separate study, she found a 4.1 bu/ac advantage on average of planting April 15 or 22 versus May 6 or 7 in 2023–2024. In the Michigan Soybean On-Farm Research program, 10 of 25 sites had significantly higher yields and only three sites had lower yields with earlier planting (2–3 weeks earlier than normal) from 2019-2023 (Fig. 4).
Planting early, although likely to result in higher yields, is not without risks. A key caveat is that none of the researchers recommend planting early unless soil conditions are right. Creating ruts, compaction/sidewall smearing and open seed trenches will likely cause problems that will more than negate any yield advantage of planting early. Soil temperatures should be approaching 50 degrees Fahrenheit and rising, and planting should be avoided if rainfall is expected within 24 hours with cold air temperatures to avoid seedling injury due to imbibitional chilling—that “first drink” for the seed being too cold.
If we have an early spring and all these conditions are right in the first half of April, ultra-early planting may be considered. Bauer’s research has found planting in the first half of April compared with planting in late April or early May resulted in higher yields 85% of the time and an average yield advantage of 1.7 bu/ac. Lower yields resulted when frost events were severe, and one field needed to be replanted. Just remember that federal crop insurance is not available with ultra-early planting.
One of the main risks to early planting is the increased risk of a frost/freeze event after seedlings have emerged. Unifoliate leaves or cotyledons subjected to 29–30 F temperatures are likely to experience injury while true trifoliates can be damaged at temperatures below 32 F. Also expect seeds to be in the ground for two weeks or longer with early planting, so consider using a fungicide seed treatment, perhaps a premium package with ultra-early planting. Including a product such as iLevo or Saltro in fields with known sudden death syndrome is also advised.
Thanks to Dr. Manni Singh and Missy Bauer for contributing to and reviewing this article. This article was produced by a partnership between MSU Extension and the Michigan Soybean Committee. The article was first published in the Michigan Soybean News magazine.
