Planting Date Effects on Soybean Growth & Yield in the Southern U.S.

Early Soybean Production System

• As soybean production has increased in the Southern U.S. over the past 20 years, the range of planting dates has expanded as well, extending from late March through late June.
• The Early Soybean Production System (ESPS), developed primarily in the southern states of Arkansas, Mississippi, and Louisiana, is a system that utilizes mid- to late-Maturity Group (MG) 4 soybean varieties planted in mid- to late-April to maximize yields.

Yield Potential

• With the ESPS, soybean flowering and early grain fill occur in cooler parts of the summer when water use efficiency is higher, thereby escaping detrimental effects of heat stress later in the summer (Figure 1).
• Perhaps more important is the fact that flowering and pod set occurs during the longest days of the year, generally resulting in higher pod counts.

Lodging Risk

• Much of the soybean production in the Southern U.S. has shifted to productive silt loam soils once reserved for cotton production. Soybeans grown on these soils are often prone to lodging, especially if soybean is planted in single wide rows and following a highly fertilized corn crop.
• It is important to employ strategies that reduce the likelihood of lodging when growing soybeans on these soil types.
• Later-planted soybeans in this region tend to grow taller, which increases their risk of lodging on highly productive soils.
• Timely planting of soybeans can help maximize yield potential, as well as harvestable yield by reducing the risk of lodging.

Mississippi State Study

• A 2-year Mississippi State University field study evaluated planting date effects on growth and yield of two soybean varieties (MG 4 and 5) at two locations.
• Planting dates in the study spanned from late March through mid-July.
• Final plant height increased with later planting for planting dates extending through early June (Figure 2).
• Soybeans planted in late March reached an average height of 32 inches, while those planted in early June were around 10 inches taller.
• Final plant height declined for planting dates after early June, with soybeans planted at the latest timing in mid-July averaging only 23 inches.

• Soybean yield was maximized with planting around April 20 and declined with successively later planting after that point (Figure 3).
• Soybeans planted around April 20 reached an average yield of over 70 bu/acre, while those planted a month later averaged around 60 bu/acre.

Pioneer Study

• Pioneer agronomists conducted a field study to evaluate the impact of planting date on yield and lodging of two indeterminate Pioneer^® brand soybean varieties (MG 4.7 and 4.9) grown on productive soils in the Mississippi Delta.
• Planting dates in this study were April 9, April 23, May 10, and May 24.

• Soybean yield of both varieties was greatest with the April 23 planting date (Figure 4).
• Soybean lodging was significantly reduced for both varieties with April planting dates compared to May planting (Figure 5).

• Results of both the Mississippi State study and the Pioneer study showed that timely planting can increase soybean yield potential, while also reducing the risk of lodging.

• Bateman, N.R., A.L. Catchot, J. Gore, D.R. Cook, F.R. Musser, and J.T. Irby. 2020. Effects of Planting Date for Soybean Growth, Development, and Yield in the Southern USA. Agronomy. 10, 596.
• Poston, D., B. Blessitt, and J. Hollowell. 2014. Planting Date and Seeding Rate Effects on Soybean Lodging and Yield. Pioneer Agronomy Research Update. Vol. 4. No. 35. Corteva Agriscience. Johnston, IA.
• Poston, D. and M. Jeschke. 2015. Optimizing Soybean Maturity Group by Planting Date Interactions in Kentucky. Pioneer Field Facts. Vol. 15. No. 1. Corteva Agriscience. Johnston, IA.