We have observed a few ears of corn at black layer, while fields planted in late April have kernels with moisture contents around 30%. As of this week we have even observed a few fields across the state being harvested. Blacklayer needs around 2700 growing degree days, which most corn planted mid to late April has passed in Sussex County, and about to reach in New Castle County (Table 1). Most fields after that are probably a week or less behind with the heat we have seen.

While it has been cooler than July, day time temperatures have cycled between the upper 80s and low 90s, which may have caused a few grain fill issues in dryland fields. The steady rainfall observed north of Dover in July has tapered off, leading to some droughty dryland corn and soybean fields. Still, the region north of Harrington is still leading the state in total rainfall, as many storms continue to pass through the center or just south of Delaware this month.

Table 1: Accumulated growing degree-days based on planting dates through July 31^st

R1 = 1400 GDD, R5 (Dent) = 2190-2450, R6 (Blacklayer) = 2700

Jarrod Miller, Extension Agronomist, jarrod@udel.edu

Unless you planted corn later in June, and some people appear to have made that choice, cornfields across Delaware should be into the reproductive stages. The easiest reproductive stage to decipher is probably R5, which is the dent stage (Figure 1). As corn grains dry down, moisture loss causes a dent near the crown as the kernel shrinks a little. Prior to dent you must estimate liquid in the kernel to determine whether you are in blister, milk, or dough stages. A guide to grain fill stages can be found here: https://www.agry.purdue.edu/ext/corn/news/timeless/GrainFill.html.

Figure 1: Corn in dent stage planted on April 24th in Georgetown, DE.

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Jarrod Miller, Extension Agronomist, jarrod@udel.edu

With the warmer mid-April temperatures, there were some fields planted a little earlier than usual (or at least earlier than last year). It takes 120 growing degree-days (GDD) to see corn emergence. Anyone who planted by Sunday, April 14^th should already have seen 120 GDD in all three counties, although it took almost nine days to get there.

Around April 18^th we had a strong warming trend before temperatures cooled back off. Had the trend remained in place, it would only have taken about a week to hit 120 GDD. The weather outlook in Georgetown over the next week remains conducive for corn germination, while the northern end of the state may see a few nights below 50°F. However, soils are insulated so we can expect soil temperature to remain in the upper 50s to low 60s. With this weather, we can still expect to see germination and emergence within 7-9 days.