Friday, August 9, 2013

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.

Wednesday, August 7, 2013

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.

Planting dates
April 10-June 15
April 14-June 18
April 13-June 17
March 28-June 15
GDUs (May 1-July 15)
GDUs (July 15-Oct 1)

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 
Aug 16-Sep 21 
Aug 18-Sep 14
Aug 10-Sep 9
R5.5: 50% Kernel milk date (DAS)
Sep 20-DNM
Sep 2- Oct 11
Sep 6-Oct 10
Aug 31-Sep 28
Forage yield (T DM/A)
Grain yield (bu/A)
Grain moisture (%)

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
Aug 18-Sep 18
Aug 20  Sep 12
R5.5: 50% Kernel milk date (DAS)
Sep 18-DNM
Aug 30-Oct 12
Sep 4-Oct 7 
Grain yield (bu/A)
Grain moisture (%)
† 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.