Should Soy Be Planted Before Corn? New Research Says Yes

If you follow mainstream wisdom on when to plant corn and soybeans, you may be missing out on the potential for a substantial soybean yield increase. New research indicates that flipping the script and getting soybeans in the ground earlier in the season could be the key to increasing yield.  

Should you plant soybeans or corn first? 

Experts are now saying you have more wiggle room regarding when to plant soybeans in relation to typical corn planting times to achieve maximum yield. Soybean yield is dependent on many factors, including field productivity, variety characteristics like temperature and pest tolerance, planting depth, length of growing season, and weather conditions. But the single most impactful factor in soybean yield is planting date. Data collected in a study of Xitavo® soybean seed across Iowa, Illinois, Indiana, and Ohio from 2016 to 2022 indicates that yield potential is reduced every day planting is delayed.¹ 

📸: BASF internal photograph/Featuring data on average Xitavo® soybean yield by planting date   

Following recommended soil condition guidelines to determine the proper planting time for your fields, as well as supporting your seeds with treatment protocols, can allow soybeans to thrive in less than ideal spring environments.  

Soybean planting dates: which month is best? 

Soy is typically planted after corn (after April 15 in the Midwest), but soybean planting dates by state and region may vary.² The recommended planting dates usually fall no earlier than 14 days before the historical last spring freeze date for your region.³  

These traditional timelines were originally established as a strategy to help reduce the impact of Soybean Sudden Death Syndrome (SDS), one of the most prevalent yield-limiting soybean diseases in North America. SDS infects young soybean roots shortly after germination, and the occurrence of SDS is more likely when cool, wet soil conditions slow seedling development.  

📸: Darcy Maulsby via iStock/Featuring soybean plant showing signs of SDS. 

Currently, however, research indicates that following conventional planting timelines isn't the only way to safeguard your crop against SDS and other early-season threats. Today, the most effective strategies for managing SDS to maximize soybean yield potential include choosing more tolerant soybean varieties as well as implementing seed treatment protocols.⁴  

In a nutshell, don't decide when to plant soybeans based exclusively on a specific date on the calendar. The calendar date matters much less than the actual conditions of the soil. Traditional soybean planting dates by state are all estimates based on the same set of factors, including soil temperature and soil moisture. Monitoring these levels is key to understanding when your soy will have the best chance of germination and growth. You can also run a cold germination test (where seeds are tested in a cold, damp environment replicating early-season soil) or cold saturated germination test (where seeds are tested on saturated soil) on each seed lot to get a good benchmark for which lots will germinate more successfully when faced with unfavorable planting conditions. 

Corn planting dates: which month is best? 

Both corn and soy require a soil temperature of at least 50 F for germination. The optimal soil temperature for soybean germination and emergence is 77 F and the optimal soil temperature for corn ranges from 60 F to 85 F, indicating that you can likely push your corn planting time out a bit further as temperatures rise.  

As with soy, monitoring soil conditions is important when determining corn planting times. In early April and beyond, soil temperature and soil workability are two of the major indicators to watch when deciding when to plant corn. Research from multiple universities revealed nearly equivalent yields for corn planted from mid-April to mid-May.⁵  

📸: @Oleksandr Yuchynskyi via Canva/Featuring a soybean field bordering corn in Spring.

However, past mid-May, corn yield begins to decline rapidly because crops aren’t able to withstand fall temperature drops to reach full maturity. This risk can be mitigated by planting earlier-maturing hybrid varieties that are more likely to mature before freezing fall temperatures hit.  

Though many factors can influence overall corn yield, research gathered from corn crops in Illinois and Minnesota concluded that the optimal final plant population for corn is not influenced by corn planting times.⁶ 

Early soybean planting benefits?  

A host of benefits connected to early planting contribute to the overall yield potential in soy crops. 

Main benefits of early planting of crops 

• Better use of available sunlight. Early-planted soybeans are better able to utilize solar radiation during the growing season because they typically produce a larger crop canopy earlier in the growing season. This crop canopy means less available sunlight will be wasted on bare soil, particularly during growth stages crucial for yield formation. 

📸: @Olha_Afanasieva via Canva & @saraTM via Canva/Featuring a comparison of scarce crop canopy vs. a large canopy in soybeans 

• Reduced moisture evaporation. By shading the soil surface, the larger crop canopy also reduces soil moisture loss due to evaporation. 

• Lengthened growth period and more pods per plant. Additionally, the earlier soybeans are planted, the longer the period of vegetative growth. The extension of this growth period increases nutrient and photosynthete accumulation, processes critical for pod and seed formation. This enables the crop to flower earlier and produce more vegetative nodes, increasing the potential for more pods per plant.⁷ 

📸: @Eny Purwanti via Canva & @Roman Budnyi via Canva/Featuring a comparison of soybean plant with low pod count vs. early-planted soybean plant with many pods. 

• Improved soybean weed control. Since early planting gives soybeans a head start in canopy growth, it also improves their competitive ability against weeds. Early canopy development is an effective management practice for limiting growth of early emerging weeds that could otherwise overtake a less mature crop.⁸ 

What soybean varieties work best for early planting? 

Greater soybean yields overall typically occur when early planting schedules are paired with very full-season varieties (+0.5 maturity group (MG)). However, to achieve this yield boost, your soybeans must be planted by the first week of May. Any yield advantage of longer-than-adapted varieties is lost if you plant in mid-May or after.  

While long-season varieties have greater yield potential, they also can have a greater yield penalty if planted late. When planted early, long-season varieties win the overall yield battle compared to shorter-season varieties (-0.5 MG). However, mid- to late-May planting dates produce yields similar for both long- and short-season varieties.⁹  

Planting the latest-maturing variety adapted for your region is also key to preventing early-planted soy from maturing too quickly in the fall. If the crop is already past the R6 growth stage when late-season rain hits, the rain will not produce the yield increase that it would for soybean plants in earlier growth stages. Late-maturing varieties also help extend the reproductive period of the crop; if early-planted soybeans encounter unseasonably warm weather after planting, plants can emerge and flower significantly earlier than usual, which will negatively impact overall yield.¹⁰ 

Because the environment changes from year to year, it is important to assess variety yield stability across multiple locations and over the course of several years. Varieties found to consistently top the charts in yield for most locations and growing seasons typically will have the best likelihood of high yields going forward.¹¹ 

Can you plant soybeans too early? 

If you are aiming to plant soybeans early so your planting time doesn't clash with corn planting, it is important to find the middle ground between planting soybeans early enough, but not too early.  

Early season conditions to watch out for 

You should avoid planting soy if you are experiencing the following conditions: 

• Low temperatures. Planting soybeans when soil temperatures are still below 50 °F is not recommended due to the increased risk it poses related to seed and seedling infection, rot, and mortality. 

• Wet seedbeds. If your seedbeds are saturated with moisture after tillage, this can create soil crusting and compaction, which is a detriment to stand establishment.

• Ultra-early planting. Planting soy as early as February in southern regions and March in northern regions is considered ultra early¹² and is not recommended due to the combination of weather and temperature risks typically present during these time frames. \\

📸: @fotokostic via Canva/Featuring compacted soil in soybean field.

Yield penalties for planting soy too late

On the other hand, if you plan your planting schedule based on the ideal soil temperature for soybean germination and emergence (77 °F), you will likely find yourself waiting until late May or early June to reach these levels. By that time, you will be imposing a significant yield penalty.  

While early planting of soybeans in colder, damper soil can affect the rate of emergence, it likely will not affect growth to such an extent that overall yield will suffer.  

How to mitigate risks of early planting of crops 

At two inches of soil depth and 50 F soil temperatures, soybeans can easily germinate. However, it is not uncommon for emergence to take as long as three weeks for soybeans to germinate at these kinds of temperatures.¹³  

This prolonged exposure to cold, damp soil conditions means soybeans planted early are at greater risk for disease as they sit in the soil for a longer period of time, and the wet soil and cold temperatures slow their emergence.  

Practices to manage early planting threats to crops 

With modern risk-management strategies to mitigate and control early-season threats, you no longer need to sacrifice your maximum soybean yield potential.  

• Implement seed treatment protocols. Cold soil temperatures also slow root development and make the crop more susceptible to soil-borne root-rotting pathogens, including Phytophthora, Pythium, Rhizoctonia, or Fusarium.¹⁴ If there is a history of these root rots in your field, using a fungicide treatment such as Obvius® Plus, which guards against seedling disease and promotes early-season stress tolerance, is recommended. 

• Combat the risk of inclement conditions by increasing seedling rates to offset mortality or putting seed treatment protocols in place, such as ILEVO® Seed Treatment, which helps protect seeds from SDS and Soybean Cyst Nematode (SCN) infections.  

• Early-season insect pressures can cause additional stand loss and early injury to seedling soybeans. Applying a broad-spectrum seed treatment insecticide that provides protection immediately, like Poncho® Votivo® Precise reduces the risk ofi nsect damage above and below ground. Additionally, biological components in Poncho® Votivo® Precise can help increase plant growth and yield by creating a biological shield against nematode damage well into the growing season.  

• Safeguard root systems. Vault® IP Plus provides added early disease protection with a rhizobia strain that increases overall nodulation while maximizing nitrogen fixation potential, proven to outperform native populations on early symbiosis and nitrogen fixation on root. Additionally, this dual-strain biofungicide helps increase nutrient and water uptake for stronger plants.  

• Use vertical tillage. Tillage practices can help improve seedbed conditions for early planting. Vertical tillage tools with straight tracking blades that break the soil open at 2” to 3” depth help create soil conditions that can dry and warm faster. This allows soybeans to emerge and create a full canopy sooner, even when planted in wet, cold conditions.15  

• Check the details of your crop insurance coverage. Additionally, if you decide to try your hand at planting soybeans early, make sure your new planting schedule doesn't impact your crop insurance policies. Crops planted prior to your policy's specified earliest planting date will not be eligible for replanting payments,¹⁶ so it is important to confirm the earliest soybean planting dates with crop insurance agents and proceed accordingly, planting at or after the Risk Management Agency (RMA) replant crop insurance dates start. 

📸: @fotokostic via Canva/Featuring a beautiful and productive soybean field.

Maximize soy yield this season with early planting of crop 

Even though early planting requires additional management to minimize early-season risks, proper proactive management of those threats can produce significantly positive results. Employing effective seed treatment protocols and proper variety selection techniques and implementing seedbed monitoring practices can ensure you are providing the best conditions for successful germination and growth, so you can reap the rewards of higher yields from early planting.  

Learn more at Grow Smart® Live: 

View our checklist for planting soybeans early and explore how to select the right soybean varieties for your situation:  

• Early Soybean Planting Checklist

• Selecting next year's soybean varieties

• Soybeans and day length

Experts are available to help you make your decisions. Reach out to your seed retailer, a nearby extension office agent, or a seed company professional like your regional BASF representative. 

________________________________________________ 

Endnotes 

1. Backhaus, Bill. "Early Soybean Planting Checklist." Grow Smart Live, 20 Feb. 2023, www.growsmartlive.com/news/5260. Accessed 7 Dec. 2023. 
2. Brooks, Rhonda. "Are 100-Bushel Soybean Yield Averages On The Horizon?" Ag Web, 8 Nov. 2023, www.agweb.com/news/crops/soybeans/are-100-bushel-soybean-yield-averages-horizon. Accessed 13 Dec. 2023. 
3. Specht, James E., and Angela Bastidas. "Planting Soybeans Early Crucial to Optimizing Soybean Nodes and Yield." CropWatch, 22 July 2019, cropwatch.unl.edu/planting-soybeans-early-crucial-optimizing-soybean-nodes-and-yield. Accessed 13 Dec. 2023. 
4. Conley, Shawn, et al. "The Best Soybean Planting Date." Soybean Research and Information Network - SRIN, soybeanresearchinfo.com/wp-content/uploads/2022/01/2700-003-23_Planting-Date-V1.pdf. Accessed 7 Dec. 2023. 
5. Simmons, Bill. "Corn hybrid relative maturity." Grow Smart Live, 4 Dec. 2023, www.growsmartlive.com/news/5466. Accessed 7 Dec. 2023. 
6. Coulter, Jeff. "Planting Date Considerations for Corn." Extension at the University of Minnesota, 2021, extension.umn.edu/corn-planting/planting-date-considerations-corn. Accessed 6 Dec. 2023. 
7. Staton, Michael. "Planting Soybeans Early Offers Many Benefits." MSU Extension, 18 Mar. 2011, www.canr.msu.edu/news/planting_soybeans_early_offers_many_benefits. Accessed 6 Dec. 2023. 
8. Everman, Wesley. "Weed Management." NC State Extension Publications, 6 Jan. 2022, content.ces.ncsu.edu/north-carolina-soybean-production-guide/soybean-weed-management. Accessed 13 Dec. 2023. 
9. Naeve, Seth. "When and How to Plant Soybean." Extension at the University of Minnesota, 2018, extension.umn.edu/soybean-planting/when-and-how-plant-soybean. Accessed 5 Dec. 2023. 
10. Staton, Michael. "Identifying and Mitigating the Risks of Ultra-early Soybean Planting." Michigan State University, 20 Feb. 2020, www.canr.msu.edu/news/risks-of-ultra-early-soybean-planting. Accessed 7 Dec. 2023. 
11. Carleo, Jenny, et al. "Keys to Success: Choosing the Right Soybean Variety." Soybean Research and Information Network - SRIN, soybeanresearchinfo.com/wp-content/uploads/2023/02/20230124_Factsheet_VarietySelection_V2.pdf. Accessed 5 Dec. 2023. 
12. Conley, Shawn, et al. "The Best Soybean Planting Date." Soybean Research and Information Network - SRIN, soybeanresearchinfo.com/wp-content/uploads/2022/01/2700-003-23_Planting-Date-V1.pdf. Accessed 7 Dec. 2023. 
13. "Soybean Planting Date Can Have a Significant Impact on Yield." Integrated Crop Management, crops.extension.iastate.edu/encyclopedia/soybean-planting-date-can-have-significant-impact-yield. Accessed 7 Dec. 2023. 
14. Malvick, Dean. "Soybean Seed and Seedling Diseases." Extension at the University of Minnesota, 2018, extension.umn.edu/soybean-pest-management/soybean-seed-and-seedling-diseases. Accessed 7 Dec. 2023. 
15. Rossman, Dan. "Vertical Tillage: Does It Fit Your Operation?" MSU Extension, 3 Mar. 2011, www.canr.msu.edu/news/vertical_tillage_does_it_fit_your_operation. Accessed 7 Dec. 2023. 
16. Mitchell, Paul, and Katie L. Wantoch. "Crop Insurance Changes for 2023." Farm Management, 2023, farms.extension.wisc.edu/articles/crop-insurance-changes-for-2023/. Accessed 6 Dec. 2023. 

Always read and follow label directions. Grow Smart, Obvius, ILEVO, Poncho, Votivo, and Vault are registered trademarks of BASF. is a trademark of BASF. Copyright 2024 BASF Corporation. All rights reserved.