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
¼	EEEX	90
½	EX	71
½	EEEXXX	69
¾	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)