While reading the Nation Corn Growers Association Yield Contest results, I was struck by the plant populations at planting and harvest. The average planting population of all entrants in the contest was 33,616 plants/A, while state winners averaged 34,821 plants/A, and national winners averaged 39,166 plants/A. The average harvest population for all entrants was 32,160 plants/A, while state winners averaged 33,833 plants/A, and national winners averaged 39,222 plants/A. If we assume that the initial plant population was the planter setting that reflects the number of seeds dropped, then seed survival for all entrants was 96%, while for state winners it was 97% survival, and for national winners it was 100% survival.

I was curious about corn seed survival in Wisconsin. We have traditionally figured that90% of the seed planted survives to produce a harvestable plant. So to establish a field at 30,000 plants/A, you would need to drop seed at 33,333 plants/A.

Corn seed treatments are required in most planting situations. These treatments protect the plant through the first four- to six-weeks of the corn life cycle. In the past the dominant seed treatment was Captan. Since 2005, we have been tracking the use of seed treatments in the UW corn hybrid performance trials and to date we have had 164 different combinations of seed treatments entered. The question that many growers have asked is,"Has corn seed survival improved in modern production systems?"

Since 2008, the UW hybrid evaluation program has used a precision planter to establish plots. The seeding rate for every plot planted in this program is 34,100 plants/A. At harvest we count the number of plants that survived in 10% of the plots. Various seed treatment combinations are used on hybrids, however, no chemical seed treatments are used in the organic trials.

Where seed treatments are used, corn seed survival averaged 91-92% and was similar in the Early, Late and Specialtytrials (Table 1). The organic trials where no seed treatments are used had 82% seed survival. The most challenging location in the program with the lowest seed survival was Seymour where survival was 84%. Other locations that had lower seed survival included Coleman, Lancaster and Marshfield. These sites ranged from 86 to 87% survival. The location with the highest seed survival was Fond du Lac at 95%.

Table 1. Corn seed survival in the UW Corn Hybrid Trials. Since 2008, all plots have been seeded at 34,100 plants/A.

Trial	N	Harvest population (plants x 1000/A)	Seed survival (%)
Early	114	31.2	91
Late	100	31.3	92
Organic	37	27.9	82
Specialty	45	31.0	91
LSD (0.05)		0.5	2

Data derived from reports available at http://corn.agronomy.wisc.edu/HT/ (Table 5 or 6).

Another study where we routinely measure seed survival is a planting date experiment at Arlington (Table 2). In this study a known quantity of seed is planted and then emerged plants are counted at V5-V6. The optimum time to seed corn at this farm is May 1. Yet, seeding around May 1 does not always result in the best corn seed survival. For example, during 2010 seed survival was 85% in early May with dates before and after where survival was 95% or greater. In most years planting during April decreased seed survival. So to achieve a target harvested population, seeding rate adjustments would need to be made and changed as the planting season progressed.

Table 2. Corn seed survival(%) at Arlington, WI.

Planting date	2013	2012	2011	2010	2009
March 26 - April 26	88	76	76	95	87
April 30 - May 8	89	86	97	85	91
May 16 - May 21	88	92	96	97	94
May 31 - June 4	90	91	95	95	98
June 15 - June 18	92	86	99	84	96
LSD (0.10)	2	5	3	3	2

Data derived fromhttp://corn.agronomy.wisc.edu/Research/under "03 Date of Planting."

Corn seed survival likely varies by field. The more challenging fields in our program are in northern Wisconsin. One exception is Lancaster where aggressive tillage is used to prepare the seedbed with soil crusting resulting in some years. Average corn seed survival seems higher than the 90% level we have traditionally used. We should probably be using 92 to 95% seed survival. However, there are numerous exceptions due to seed quality, planting date, tillage system, seed treatment and hybrid.