David Moseley, LSU AgCenter Soybean Specialist

Article Highlights:

• Included in this article are the optimum planting timings for soybean in the Northeast, Central, and Southwest Louisiana regions based on a recent article from the Agronomy Journal.
• It is possible to achieve near full yield potential and reduce the risk of a severe weather event by planting soybean within a certain time frame.

Data from soybean trials conducted between the 2013 – 2020 seasons in the Northeast, Central, and Southwest regions of Louisiana were used to publish an article in Agronomy Journal called “Soybean planting dates and maturity groups: Maximizing yield potential and decreasing risk in Louisiana" (Moseley et al., 2024). The data in this article suggest there are planting windows in each region that 99 - 100% of the max yield potential can be achieved.

Northeast Region:

Even though there were varieties with different maturity groups in the Northeast Louisiana region, there was not a significant difference in yield according to maturity group. This does not mean there is not a most optimum maturity group in the Northeast Louisiana region, but there were not enough data points to separate the maturity groups using statistics.

Table 1. Most optimum planting date in the Northeast Louisiana region and the planting window to achieve 99% of yield from the most optimum planting date.

Central Region:

There were enough data points in the Central Louisiana region to suggest planting windows for 99% yield of the optimum planting date for maturity group sections of 3.0-4.4, 4.5-4.7, 4.8-4.9, and 5.4+.

Table 2. Most optimum planting date by maturity group section in the Central Louisiana region and the planting window to achieve 99% of yield from the most optimum planting date. This table is from Moseley et al. (2024).

Southwest Region:

There were enough data points in the Southwest Louisiana region to suggest planting windows for 99% of the optimum planting date for maturity group sections of 3.0-4.4, 4.5-4.7, 4.8-4.9, 5.0-5.3, and 5.4+.

Table 3. Most optimum planting date by maturity group section in the Southwest Louisiana region and the planting window to achieve 99% of yield from the most optimum planting date. This table is from Moseley et al. (2024).

The amount of yield loss when planting earlier or later than the optimum timing will depend on the environment of the growing season.

Last year there was an estimated economic damage of $23.7 million to the Louisiana soybean crop due to a prolong period of excessive rain including hurricane Francine between August 28 to September 12 (Guidry, 2024). Fields planted by April 16 at the Dean Lee Research and Extension Center were already harvested and fields planted on May 6 or later were not damaged by the extended rainy period. However, soybean plants that were planted at the Dean Lee Research and Extension center between April 17 – May 5 suffered extensive yield and quality loss.

Decreasing the risk of severe weather events by spreading out the planting dates may be one strategy to consider. Based on this data, the planting date for each region can be spread between the dates shown in tables 1, 2, and 3 and still achieve 99 - 100% of the yield of the optimum planting date.

Planting in March does come with the threat of freezing temperatures that can kill plants. The National Centers for Environmental Information shows a map of the expected last freeze across the United States. The map shows some areas in north Louisiana can have a last freeze between March 16 – 30.

Additional information can be found in the Moseley et al. (2024) article and in a Science For Success factsheet called The Best Soybean Planting Date.

References:

Conley, S., Holshouser, D., Inman, M., Lee, C., Lindsey, L., Licht, M., Kandel, H., Kleinjan, J., Knott, C., Naeve, S., Nafziger, E., Ross, J., Singh, M., Specht, J., Vann, R. The best soybean planting date. United Soybean Board. The Best Soybean Planting Date

Guidry, K. (2024). Estimates of the economic impacts on the Louisiana Agricultural Industry from Hurricane Francine. LSU AgCenter. Staff Report No: 2024 - 74

Moseley, D., Reis, A., Gentimis, T., Campos, P., Copes, J., Netterville, M., Egbedi, P., Harrell, D., Kongchum, M., Levy, R., Padgett, B., Soignier, S., Scroggs, D., Sanders, J., Pankey, J., & Fic, K. (2024). Soybean planting dates and maturity groups: Maximizing yield potential and decreasing risk in Louisiana. Agronomy Journal, 1–12. https://doi.org/10.1002/agj2.21626