If you’ve attended any winter meetings the last couple of years, one of the biggest topics when it comes to increasing soybean yield potential is planting date. It is a popular topic for those wanting to raise an operation’s soybean yield potential. It is relatively easy to do since there is limited additional investment needed, just a change in thinking. Common thought is that soybean plants flower near the time of the summer solstice and there is not much that can be done to lengthen the flowering period. Higher yields are often driven by more seeds on a plant, and one easy way to get more seeds is to have more flowering sites or more nodes. An increase in nodes can be accomplished by lengthening the amount of time the soybean is growing. Earlierplanting starts the growing degree day (GDD) accumulation earlier, and an earlier planted soybean crop should begin to flower earlier than a later planted crop. A Purdue University study found that a set number of GDDs were required to reach R1 regardless of the planting date.1 This means an earlier-planted soybean plant spent more time in the R1 flowering stage versus a later-planted one, enabling more production sites for pods.
Forcing the flowering date earlier in the growing season should allow more time for the plant to grow and accumulate dry weight for the developing seeds. In studies conducted at the Monsanto Learning Center at Monmouth, Illinois, earlier planting dates have consistently shown an increase in yield potential versus earlier planting dates. In 2017, that advantage was 5.4 bushels/acre (Figure 1).
From a multiyear perspective spanning 2015 through 2017, the advantage to planting a soybean crop earlier has demonstrated a 4.0 bu/acre average increase and tends to be in line with other university studies (Figure 2). Is planting earlier a guarantee to potentially higher yields? Absolutely not, but the data supports the recommendation. In most years, an earlier-planted soybean crop may have the potential for increased yield. How early is dependent upon local growing conditions and each grower’s level of risk tolerance.
Agronomic considerations for planting earlier:
1Casteel, S. 2010-11. Soybean physiology: How well do you know soybeans? https://www.agry.purdue.edu/ext/soybean/Arrivals/10SoyDevt.pdf.
Effects of planting date on soybean yield. 2017. Agronomy Advice. Channel.com. http://www.channel.com/agronomics/Documents/AgronomicContentPDF/EffectsofPlantingDateonSoybean-Jan8-Channel-Corn.pdf.
Early soybean planting considerations. Agronomy Advice. Channel.com.https://monsanto.com/app/uploads/2017/05/fungicide-response-planting-date-soybean.pdf.
Effects of fungicide and planting date on soybean yield. 2017. Channel.com.http://www.channel.com/agronomics/Documents/AgronomicContentPDF/EffectsofFungicideandPlantingD-Jan9-Channel-Corn.pdf.