Iowa State University Extension and Outreach

East-Central and Southeast Iowa Crop Information

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May 9, 2005

May 9, 2005

CORN
Frost Recovery

While most corn fields should now be recovering well from the frost, a few fields have extensive areas where it is questionable if thrifty plants will survive at acceptable populations.

Healthy plants should all be now showing good new growth.  In areas where the soils were dry and where temperatures were very cold, some growing points were killed and are now soft, mushy, and brown.  Apparently the dry soils allowed the soils to freeze to the depth where the growing points were.  Tilled soils seem to have been more prone to this.  In addition, injured tissues may be susceptible to bacterial soft rot, which may injure or kill the growing points, again resulting in soft, mushy tissue at the growing points, with the tissue taking on a brownish color as the tissue dies.  I have received a report of growing points that appear healthy but with a rounded tip as opposed to a normal arrow-shaped tip; it is very questionable if such plants will develop into normal plants.

In fields with considerable damage to growing points, what is a keeper stand?  This, of course, depends on the stand population and uniformity of stand.  Table 1 shows the effects of stand density and planting date, assuming uniform stands.  Table 2 shows the effect of missing plants.  Remember to consider both all of the costs of re-planting and the loss of yield due to later planting.  Also, what if the new stand has a less-than-perfect population and uniformity?

 

 

Table 1.  Influence of planting date and plant population on corn grain yields

Stand X 1,000

April 20 - May 5

May 13 - May 19

May 26 - June 1

June 10 - June 16

June 24 - June 28

28 32

100

99

90

68

52

24

94

93

85

64

49

20

81

80

73

55

42

16

74

73

67

50

38

12

68

67

61

46

35



Table 2.  Effect of stand loss (missing plants) on corn grain yield

Proportion of Missing Plants

Reduced Stand

% of Maximum Yield

EEEX

90

EX

71

EEEXXX

69

EXXX

49

The "Reduced Stand" column represents the pattern of missing plants, with E representing a surviving plant and X representing a missing plant.

For more information, see:

Pm-1885 "Corn Planting Guide" (source of Table 1 above - Table 7 on page 6 of Pm-1885)

 

NCR 244 "Uneven Emergence in Corn" (source of Table 2 above - Table 4 on page 3 NCR 344)

 

 

If you have any questions, please feel free to contact the Iowa State University Extension Office.
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Last Update: May 9, 2005
Contact: Virgil Schmitt vschmitt@iastate.edu


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