Corn Kernel Development During 2009-2012

Due to late-planting dates, the 2013 growing season is shaping up to be one of the most uneven seasons for plant  development. Nearly 30% of our corn was planted during June and many fields were finally planted the week of July 4 (Figure 1). As we near harvest, corn from these fields will likely be sold as silage to dairy farmers. In a previous article we talked about the theory of late planted corn on kernel maturity and the implications for yield and quality. In this article I would like to present field data of kernel development from experiments conducted at Arlington, WI.

Figure 1. Wisconsin corn planting progress (Data source: USDA-NASS).

These experiments had five planting dates involving different maturities of corn. Corn development stages were determined for each plot by noting the first date each reproductive growth stage was achieved (Table 1). Data from the first and last planting date is shown in Table 1. The growing season of 2009 was characterized as cool and wet, while 2012 was hot and dry. The number of days to get from silking (R1) to the denting stage (R5) was 28-45 days depending upon year, planting date and hybrid maturity. For kernels to develop from silking to 50% kernel milk required 45-62 days.

Table 1. Kernel development of full- and shorter-season corn hybrids at Arlington, WI.

	2009	2010	2011	2012
Planting dates	April 10-June 15	April 14-June 18	April 13-June 17	March 28-June 15
GDUs (May 1-July 15)	932	1156	1038	1253
GDUs (July 15-Oct 1)	1069	1327	1264	1309
Full-season Hybrid	Pioneer 35F40	Pioneer 35F40	Pioneer 35F44	Pioneer 35F48AM1
Relative Maturity (days)	105 d RM	105 d RM	105 d RM	105 d RM
R1: Silking date	July 24-Aug 16	July 16-Aug 11	July 20-Aug 9	July 9-Aug 6
R5: Denting date (DAS) †	Sep 3-Sep 28  (41-43)	Aug 16-Sep 21  (31-41)	Aug 18-Sep 14  (29-36)	Aug 10-Sep 9  (32-34)
R5.5: 50% Kernel milk date (DAS)	Sep 20-DNM  (57-DNM‡)	Sep 2- Oct 11  (48-61)	Sep 6-Oct 10  (48-62)	Aug 31-Sep 28  (48-53)
Forage yield (T DM/A)	11.0-7.2	10.0-7.5	10.1-7.2	8.7-7.3
Grain yield (bu/A)	224-118	255-51	224-155	236-106
Grain moisture (%)	24-40	15-40	17-29	19-50
Shorter-season hybrid	Jung 7426VT3	Jung 7426VT3	Dekalb DKC48-37	---
Relative Maturity (days)	96 d RM	96 d RM	98 d RM	---
R1: Silking date	July 25-Aug 17	July 16-Aug 12	July 19-Aug 7	---
R5: Denting date (DAS) †	Aug 31-Oct 1  (38-45)	Aug 18-Sep 18  (33-38)	Aug 20  Sep 12  (28-36)	---
R5.5: 50% Kernel milk date (DAS)	Sep 18-DNM  (54-DNM)	Aug 30-Oct 12  (45-61)	Sep 4-Oct 7  (48-61)	---
Grain yield (bu/A)	271-144	235-138	231-177	---
Grain moisture (%)	20-41	13-39	15-27	---

† DAS= Days after silking; ‡ DNM= Did not measure

As planting date is delayed the number of days required to reach various reproductive stages increased. To predict whether corn will mature before frost note the hybrid maturity, planting date and tasseling (silking) date of the field. For silage planted early, add 42-47 days on to this date to predict 50% kernel milk, while for grain, add 55-60 days to predict maturity. For later planting dates an additional 7-10 days may be required. These dates are guidelines which will require further in-season decisions as the season unfolds.