With the cool weather we have been having farmers are concerned about stand establishment of corn. Over the last couple of weeks wide-spread areas of the state have been frosted a number of times. Although 26% of corn crop had been planted by May 1, only 1% had emerged so little damage should be expected to these fields due to frost. Field conditions in general have been fairly good. With a little warm weather the corn seed planted should make good progress emerging over the next few days.

Typically when seeding a corn field, extra seed (~10%) is dropped to allow for seed death due to predation, pest damage, soil crusting, problems with emergence, etc. Some agronomists question this practice because of the advances in seed treatment technology that have occurred over the past decade. Emergence of corn seed in Wisconsin is challenging because of the cool, wet soil conditions we typically experience at planting. This article summarizes the effect of planting date on corn seed survival.

During the growing seasons between 2000 and 2004, two hybrids were planted (full- and short-season) on different dates into a Plano silt loam soil at Arlington, WI. Each 8-row plot was over-seeded and at V6 the plants emerged were counted and then thinned back to a final harvest stand of about 30,000 plants/A. The number of plants that had emerged at V6 for each row was divided by the number of seeds planted for each row and multiplied by 100 to calculate percent survival.

In all years, planting date affected corn seed survival. April planting dates had seed survival ranging from 64 to 95% and averaged 79% (Table 1). Seed survival between May 1 and May 15 ranged from 62 to 92% (average = 83%), between May 16 and May 31 was 80 to 96% (average = 88%), and during June was 84 to 98% (average = 92%). April planting dates were riskier for survival than May planting dates, but often conditions could cause just as much plant death during May as April. In fact, during 2004 the lowest average seed survival occurred on May 20.

In 3 of 5 years hybrids differed for seed survival. In 2 of 5 years interactions between planting date and hybrid occurred where hybrids had different amounts of survival depending upon the planting date.

Some guidelines for corn seed survival as affected by planting date:

Over-seeding your target population by 10% is still a reasonable recommendation for Wisconsin farmers for all planting dates.
June planting dates have better seed survival than May dates followed by April dates. Although, good and poor survival can be seen on any planting date during April and May.
Seed treatments are important and may help when planting early, since there is inherently more stress in Wisconsin's cool, wet soils.

Table 1. Survival (%) of corn seed planted on different dates at Arlington, WI (n= 6 plots or 48 rows).
2004		2003		2002		2001		2000
Planting date	Seed Survival	Planting date	Seed Survival	Planting date	Seed Survival	Planting date	Seed Survival	Planting date	Seed Survival

April 12	85	April 15	83	April 15	66	April 18	79	April 18	70
April 30	95	May 3	62	April 30	64	May 1	91	April 28	86
May 12	91	May 13	80	May 10	83	May 15	92	May 15	80
May 20	80	May 19	88	May 20	96	June 1	91	June 9	93
June 1	98	June 2	90	May 31	92	June 14	84	June 19	91
June 15	94	June 13	90	June 10	89
Mean	91	Mean	82	Mean	82	Mean	87	Mean	84
LSD(0.05)	5	LSD(0.05)	5	LSD(0.05)	9	LSD(0.05)	3	LSD(0.05)	4