Growing Degree Days Through June 18

Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu

Corn planted on April 24th in Georgetown has just hit the V12 stage, close to the expected GDD of 870 (Table 1). We have observed a few fields of corn tasseling, which would fit the April 14th GDD in Sussex County. Any corn planted in late May has passed V6, and should have been sidedressed, while fields planted in early June are probably close or at V6.

Table 1: Accumulated growing degree-days based on planting dates through June 18th.

If you planted

Sussex Kent New Castle
14-Apr 1128 1084 1024
21-Apr 1038 992 938
28-Apr 956 917 858
5-May 856 836 786
12-May 755 738 696
19-May 685 673 636
26-May 545 537 502

V6 = 475 GDD, V12 = 870 GDD, VT = 1135 GDD, R1 = 1400 GDD

As we approach tasseling and pollination it is a good idea to start watching day and night temperatures (Figure 1). They have exceeded 92°F during the day and 72°F at night in the past few days, which could hamper pollination and set back yield. While you can’t change the weather, you can account for the effects when trying to determine if your management or weather were the deciding factor in the final yield.

Rainfall still has a steady, linear increase across the state (Figure 2). How it affects planting and field conditions depends on where you are at. Newark has pulled ahead in total rainfall since April 14th with 13.5 inches, while Delmar is the lowest with 11. The larger rainfall events from Harrington north in the last week may be slowing soybean planting on tilled fields.

Figure 1: Statewide temperatures since April 1st.

Figure 2: Statewide rainfall accumulation since April 1st.

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