The planting season of 2004 will be long remembered by farmers in the eastern half of Wisconsin. In fact, most farmers would like to forget it! If fields were not planted by the first week of May, they often didn't get planted until the end of June. In addition, the growing season was one of coolest on record with total GDU accumulation only slightly greater than 1992. What are some lessons we might learn as planting date is delayed, especially during a cool growing season?

At Arlington, two hybrids AgriGold A6333Bt (104 day RM) and NK Brand N32-L9 (94 day RM) were planted on various dates between April 12 and June 15. Planting date x hybrid interactions were measured for grain yield, forage yield and milk per ton (Table 1).

For both hybrids, the April 30 planting date produced the greatest grain yield. Grain yield decreased with later planting date, more so with A6333Bt than with N32-L9. Both hybrids produced similar grain yield on June 1, but A6333Bt was 8.4 points higher in moisture so that economically the time to switch hybrids occurred sometime after the May 12 planting date. The last planting date, June 15, did not produce adequate grain yield for either hybrid.

Forage dry matter yield was greatest for early planting dates, and then decreased 41 to 50% as planting was delayed to June 15. A6333Bt was had a greater decrease of forage yield than N32-L9. Forage yield of 5.0 to 5.4 T dry matter/A could be achieved with June 15 planting, which is comparable to other emergency forages that would be available. Forage quality estimated using Milk per ton was similar for most of the planting dates, except for the last planting date of the full-season hybrid (A6333Bt).

These data stress the importance of switching hybrids as the planting season progresses. They also illustrate the yield and forage quality impacts that can be seen in a cool growing season.

Table 1. Response of corn to planting date during 2004 at Arlington, WI.
	Grain yield (bu/A)		Forage dry matter yield (T/A)		Milk per ton (lbs milk/T)
Planting date	AgriGold A6333Bt	NK Brand N32-L9	AgriGold A6333Bt	NK Brand N32-L9	AgriGold A6333Bt	NK Brand N32-L9
April 12	219	177	9.9	8.1	3550	3400
April 30	234	189	9.6	9.1	3400	3370
May 12	192	172	8.4	8.5	3400	3320
May 20	173	160	8.0	7.9	3560	3370
June 1	147	142	7.9	7.4	3510	3530
June 15	19	39	5.0	5.4	3160	3500
LSD(0.10)	11		1		150