In a series of studies across Maryland and Delaware, no yield benefit was observed from early planting of soybeans. However, there was also no yield penalty from early planting, providing Mid-Atlantic farmers with the confidence to plant early if they desire while tempering expectations of major yield impacts.
Mid-Atlantic Farmers are Curious about Planting Soybeans Early
Recommended soybean planting date in the Mid-Atlantic region is mid-April to late May. Prior to mid-April, the far western areas of the region are susceptible to late season frost, generally preventing some farmers from planting soybeans early.
However, data from other regions in the US, namely the South, demonstrate soybean yield increases with early planting and Mid-Atlantic farmers hypothesize they too could experience yield benefits from early planting.*
Common Questions about Early Planting
- Would more plant growth increase yield?
- Could earlier harvest = earlier cover crop planting and more financial incentives?
- Would planting early increase exposure to factors like wet, cold soil and slugs?
- How do I adjust other variables (seeding rate, maturity group) when planting early?
To Plant Early or Not? A Story in Three Studies
Researchers in the region evaluated the yield impacts of early planted soybeans through multiple trials to provide guidance to farmers interested in shifting planting dates.
Study 1: Planting Date (PD). This study focused only on planting date effects on yield.
Study 2: Variety Trials: PD x Maturity Group (MG). This study duplicated the University of Maryland variety trials for a wide range of varieties and maturity groups.
Study 3: PD x Seeding Rate x Limited MG: This study combined multiple management factors, including planting date, maturity group and seeding rate and their interactive effects on grain yield.
Study Results
Generally, the series of studies did not demonstrate a soybean yield benefit with early planting in the Mid-Atlantic. Yield increase with early planting was observed in one of the studies, but may be due to the number of observations within that study.
>> No yield benefit from early planting, but also no yield penalty from early planting.
The planting dates in the series of studies were not exceptionally early, and we struggled to plant soybeans even in early April in the region. This reflects the conditions facing Mid-Atlantic growers that tend to prevent soybean planting earlier than this date.
While our studies do not present a clear yield benefit from early planting, we did not demonstrate a yield penalty from early planting. These conclusions are important for Mid-Atlantic growers who are contemplating planting soybeans earlier. While they may not expect a yield benefit, they can ease fears of yield loss due to early planting, especially in the central and Eastern areas of MD and within DE.
Author: Nicole Fiorellino, University of Maryland. February 2025
References:
Bastidas, A.M., T.D. Setiyono, A. Dobermann, K.G. Cassman, R.W. Elmore, G. L. Graef, and J.E. Specht. (2008). Soybean Sowing Date: The Vegetative, Reproductive, and Agronomic Impacts. Crop Science, 48, 727–740. https://doi.org/10.2135/cropsci2006.05.0292
Egli, D.B. and P.L. Cornelius. (2009). A Regional Analysis of the Response of Soybean Yield to Planting Date. Agronomy Journal, 101, 330-335. https://doi.org/10.2134/agronj2008.0148
Hu, M. and P. Wiatrak. (2012). Effect of Plant Date on Soybean Growth, Yield, and Grain Quality: Review. Agronomy Journal, 104, 785-790. https://doi.org/10.2134/agronj2011.0382
