Accumulated Heat Units are Pushing Corn Along

Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu; Cory Whaley, Sussex Co. Extension Ag Agent, whaley@udel.edu; James Adkins, Irrigation Engineer, adkins@udel.edu, Jake Jones, Extension Agriculture Agent, Kent County, jgjones@udel.edu; Dan Severson, Agriculture Agent, New Castle County, severson@udel.edu

Corn at the research station planted in late April has begun to show kernels at R5 (dent stage, 2190 to 2450 GDD) and is rapidly approaching blacklayer (2700 GDD). Due to the cooler weather in late April, most mid-May fields are not very far behind (Table 1, Figure 1). Temperatures have stabilized somewhat since the beginning of August, with fewer days above 87°F, particularly in New Castle County. Since mid-July, Sussex county has had at least 11 nights with temperatures greater than 72°F, which may also have slowed corn growth and grain production.

At this time last year, we had accumulated 21, 20, and 16 inches of rainfall in Newark, Dover, and Georgetown, respectively. This year we have accumulated 11, 24, and 16 inches in those same parts of the state (Figure 2). Until the recent tropical storm, Kent only had 16 inches, so much of the recent rainfall has probably runoff the field rather than infiltrated. Growers should continue to irrigate their fields until blacklayer is reached.

Table 1. Accumulated Growing Degree Days Based on Planting Date

Figure 1. Growing degree day accumulation since April 15^th.

Figure 2. Statewide rainfall accumulation since April 15^th.