Will Corn Mature This Year? - Projected Silking Dates

Joe Lauer , Corn Agronomist

So far the 2004 corn growing season (May 1 to July 21) has been one of the coolest and wettest seasons on record at the Arlington and Marshfield Agricultural Research Stations (Figures 1 and 2). At Arlington a total of 1050 growing degree units have accumulated, which is the lowest total GDU accumulation for this period since records were kept beginning in 1962 (Table 1); it is the fourth wettest year. At Marshfield , the growing season between May 1 and July 21 has been the fourth coolest over the past 50 years and the sixth wettest.

A 105-110 d RM corn hybrid will silk after 1250 GDUs have accumulated. A 90-95 d RM corn hybrid will silk after 1150 GDUs have accumulated. We can predict when corn will silk for various planting dates at Arlington and Marshfield during 2004. We will assume that weather will be average beyond July 21 (highly unlikely).

Using a benchmark of 1250 GDUs at Arlington, corn planted April 15 should silk July 25; planted May 1, silk July 31; planted May 15, silk August 5; planted June 1, silk August 13; planted June 15, silk August 24; and planted July 1, silk August 31.

At Marshfield a 90-95 d RM hybrid requiring 1150 GDUs, planted April 15 would silk July 25; planted May 1, silk July 31; planted May 15, silk August 4; planted June 1, silk August 11; planted June 15, silk August 21; and planted July 1, silk August 30.

Next week I will provide projected dates for dent (R5), 50% kernel milk dates and (R5.5), and kernel maturity (R6 – black layer).

Table 1. Years with lowest total Growing degree units (modified method: base= 50 and maximum = 86) and greatest precipitation (inches) between May 1 and July 21.
Arlington (since 1962)   Marshfield (since 1955)
Year GDUs Year Precipitation   Year GDUs Year Precipitation
2004 1050 2000 20.6   1967 957 1984 18.1
1969 1138 1978 18.9   1958 976 1968 16.8
1967 1139 1993 18.1   1960 984 1993 16.6
1997 1164 2004 15.2   2004 986 1978 16.5
1968 1173 1994 15.0   1969 988 1973 15.2
1993 1178 1984 14.0   1979 1060 2004 14.2
1992 1178 1969 13.8   2003 1065 1969 14.0
1996 1190 2001 13.8   1968 1071 2002 13.8
1974 1198 1996 13.3   1965 1074 1957 13.8
2003 1199 1998 13.0   2000 1087 1991 13.6


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