Soybean Planting Timing Decisions

Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu; Cory Whaley, Sussex Co. Extension Ag Agent; whaley@udel.edu and Alyssa Koehler, Extension Field Crops Pathologist; akoehler@udel.edu

At the Carvel research station, we have been examining planting date, yields, and nutrient uptake on soybeans with support from the Delaware Soybean Board. In 2020 our early planting date was restricted to May 8^th, but in 2021 we planted April 12^th, and have also planted this year on April 13^th. In both years we planted a 4-2 maturity group soybean.

In both 2020 and 2021 we saw no yield differences by planting from April 12^th up until June 4^th (Table 1). We did observe some stand issues in 2021 (Figure 1), where one of the row units had a bad spring and planted too deep. The same planter had no issues with later plantings though, so our untreated seeds probably succumned to cool temps, higher moisture, and a deeper seed placement.

We also noticed some differeces in nutrient uptake by planting date both years, where tissue samples were taken in late July (R2 growth stage). More Ca, S, and Fe have been taken up with earlier plantings (varies by year), while Mg, Zn, Mn, were all higher in soybean tissues planted later in May. All nutrients were within sufficiency ranges, however you can expect differences in tissue concentrations by planting date. Ealier planting both years had much higher concentrations of Al, which is toxic to plant roots and not an essential nutrient. This may be limiting yield in our region with earlier plantings, but more work should be done.

Overall, earlier planting has not increased yield, but has also not reduced yield, so this earlier planting may help spread out field work. However, these were all planted in an irrigated, sandy soil in southern DE, which may not reflect all conditions across the state.

Keep up with your regional conditions through DEOS (http://www.deos.udel.edu/).

Table 1. Soybean yields by planting date in 2020 and 2021.

Figure 1. Some rows did not emerge in our 2021 mid-April planting due to planting depth issues. Later planting didn’t cause the same issues.