Growing Degree Days (GDD) and Rainfall Through August 7th

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

Later planted fields (mid-June) should be undergoing pollination, but temperatures this week are in the low 90s, possibly affecting pollination. Most fields planted in late May were pollinating during ideal conditions, although weather and soil moisture could certainly vary across the state. If you have good records of when you have planted, take a look in a week or two and check for tip-back or aborted kernels along the ear. Fields planted in early April may be in blacklayer within the next week to ten days, if we keep getting about 30 growing degrees per day. Let us know if you see anything sooner. In the last week we have actually seen lighter rainfall every few days, instead of intense storms or extended drought. It is still a good idea to check soil moisture levels and irrigate if necessary.

VT: 1135 GDD – Pollination can begin
R1: 1400 GDD – Silking, pollination
R6: 2700 – Blacklayer

Table 1: Accumulated growing degree days based on planting dates through August 7th.

If you planted

Sussex Kent New Castle
22-Apr 2374 2329 2250
29-Apr 2322 2282 2216
6-May 2214 2172 2118
13-May 2110 2067 2021
20-May 1998 1960 1927
27-May 1841 1801 1779
3-Jun 1688 1649 1628
10-Jun 1565 1532 1514
17-Jun 1429 1405 1386

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