Assessing Hail Damage in Corn

This past Tuesday evening, an intense storm with hail and high winds swept through northern Wisconsin. Some hail damage has been reported in western Wisconsin. Any corn knocked down by wind will likely recover since it is still early enough in the growing season and the stalk and leaves are still green.

Hail affects yields primarily by reducing stands and defoliating the plant. Defoliation causes most of the loses. Knowing how to recognize hail damage and assess probable loss is important for decision making.

The keys to storm related damage of crop fields are to: 1) be patient, 2) determine the crop growth stage, and 3) assess plant health accurately. Go ahead and view the damage, but do not make any assessments until 7-10 days have passed because it is difficult to distinguish living from dead tissue immediately after a storm, It will take that long for the corn plant to begin growing again if it can. For guidelines on assessing hail damage click here.

Hail adjusters use standard tables to calculate compensation for yield loss associated with hail. Four assessments are made on corn when hail occurs after silking (Vorst, 1990) including:

1. Determining yield loss due to stand reduction,
2. Determining yield loss due to defoliation,
3. Determining direct ear damage, and
4. Bruising and stalk damage.

It is important to work with your crop insurance adjuster before any final decisions are made. 

Further Reading

Lauer, J.G., G.W. Roth, and M.G. Bertram. 2004. Impact of Defoliation on Corn Forage Yield. Agron J 96:1459-1463.

Roth, G.W., and J.G. Lauer. 2008. Impact of Defoliation on Corn Forage Quality. Agron J 100:651-657.

Vorst, J.V. 1990. Assessing Hail Damage to Corn. National Corn Handbook NCH-1:4 pp.

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.

Will Corn Mature Before Frost?

The following article is a summary of a field day presentation for the Dodge/Fond du Lac County Corn Growers Association on July 24 at Lamartine, WI.  PDF. 

During cool growing seasons, especially when planting is delayed due to wet spring conditions, growers are concerned about whether their corn is vulnerable and will reach maturity before normal frost dates. Often the range in planting dates have implications at harvest time, especially for silage because grain and dairy producers often negotiate the sale of corn in fields that are borderline for development.

Most hybrids require about 55 to 60 days to develop from the silk stage to physiological maturity. Hybrid maturity differences in development time occur primarily from emergence to silking, not from silking to maturity.

Most concern exists when corn does not reach the silk stage (R1) until early August or later. Killing frosts can easily occur by late September, so corn silking in early August would not be safe from major yield reductions due to frost until early October.

Figures 1 and 2 describe typical development of corn silage yield and quality and of a corn kernel. At the dent stage (R5), corn has accumulated 75-85% of silage yield and 60-75% of grain yield and needs about 27-32 days to avoid significant yield reductions due to frost (Table 1). In order to avoid yield reductions caused by frost, corn intended for silage should be silking by late August, while corn intended for dry grain should reach the dent stage by September 1.

Figure 1. Corn silage yield and quality changes during development.

Figure 2. Typical corn kernel development in Wisconsin.

Table 1. The relationship between kernel growth stage and development.

Stage	Calendar days to maturity	GDUs to maturity	Percent of maximum yield  Grain                Silage		Moisture content (%) Grain                Silage
R1: Silking	55-60	1100-1200	0	45-50	---	80-85
R2: Blister	45-50	875-975	0-10	55-60	85-95	80-85
R3: Milk	35-40	750-850	10-30	60-65	70-85	80-85
R4: Dough	30-35	650-750	30-60	65-75	60-70	75-80
R5: Dent	27-32	425-525	60-75	75-85	50-55	70-75
R5.5: 50% Kernel milk	13-18	200-300	90-95	100	35-40	65-70
R6: Black layer	0	0	100	95-100	30-35	55-65

To predict whether corn will mature before frost note the hybrid maturity, planting date and tasseling (silking) date of the field. For silage, add 42-47 days on to this date to predict 50% kernel milk, while for grain, add 55-60 days to predict maturity. These dates are guidelines which will require further in-season decisions as the season unfolds.