Soil Temperatures and Growing Degree Days

Jarrod O. Miller, Extension Agronomist,

Minimum soil temperatures for planting are 50°F to obtain good germination and emergence from corn and soybeans. Based on DEOS (, soil temperatures were above 60°F across most of the region on April 17th (Figure 1a). Based on average soil temperatures for the second half of April in 2023, we can expect conditions to stay ideal (Figure 1b).

Jarrod Soil Temperatures 4-18-2024 Corn Planting

Figure 1: Current soil temperatures across the region (a) compared to average soil temperatures during the last two weeks of April in 2023 (b).

GDD Time for Delaware 4-18-2024 Jarrod Miller

Figure 2: Growing degree day accumulation in the last half of April 2023 (a) and the April 2024 rainfall totals through the 17th (b).

Based on past growing degree information for Delaware ( , corn emergence may occur anywhere from 84-150 GDD, with an average of 109 GDD. A more nationally recognized value for corn emergence is about 120 GDD for 50% of your stand. During the second half of April in 2023 (Figure 2a), Sussex County met this threshold. Any corn planting done this week should emerge by May 1st, but northern parts of the state can expect delays in emergence. However, due to the excessive rainfall that has also occurred further north (Figure 2b), field conditions may be too poor to plant in New Castle and northern Kent County.