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