From seed to harvest, corn faces many stresses
After a corn seed is planted, it is a wonder that the seed can survive and return 400 to 600 fold or more. If Wisconsin's cool, wet spring soils do not kill the plant through imbibitional chilling, then seed rotting pathogens or hungry insects can attack and kill the seed.
Once the plant emerges, it is subject to even more biotic and abiotic stresses that can often kill the plant. Even management operations like wheel traffic and cultivator blight can inflict significant harm. It is a wonder ...
I often get the question, "How much seed survives to produce grain yield?" The question is motivated by the fact that seed costs have risen dramatically in the bio-tech era of corn hybrid development (1996 to present). Some of the rising cost of seed is due to growers planting fields to higher plant densities.
Between 1982 and 2017, growers in Iowa, Illinois, Indiana, Minnesota and Wisconsin have increased plant population at the rate of 261 to 309 plants/A*yr . In our experiments, the corn plant density that produces maximum yield has been increasing over time at the rate of 260 plants/A*yr.
However, most of the rising seed cost is due to the use of bio-engineered traits in modern corn hybrids. In the 1990s, a high performing adapted corn hybrid cost about $25 to $30/A ($80 to $125 per 80K bag or $1.00 to $1.56 per 1000 seeds). Today, typical retail seed prices are $100 to $150/A ($250 to $350 per 80K bag or $3.13 to $4.34 per 1000 seeds).
Since both seed cost and field plant density are increasing, growers are increasingly concerned about how much seed actually survives to emerge and grow into a plant that produces grain yield. In a previous article I summarized the effects of planting date and environment on corn seed survival in a previous article that adds more data to the discussion and looks at recent trends in corn seed survival.
Prior to 2008, we planted corn hybrids in UW trials by over-seeding and hand-thinning back to a uniform plant density. In 2008, we purchased a precision plot planter and dropped a uniform 34,100 seeds/A at every test site during the 2008 to 2015 planting seasons. In the winter of 2015, we had the planter refurbished and upgraded with new software set to drop 34,850 seeds/A since then. At harvest, plant population was measured on ~10% of the plots. All data collected since 2008 (N= 12,036 plots) were used in the analysis.
Seed survival in the traditional corn hybrid trials where chemical seed treatments are used, averaged 91%, and depended upon environment (year and location), cropping system, and seed company. Seed survival during 2012 (drought) was lowest at 82%, while seed survival was highest at 95% during 2009 (wet spring).
In organic trials where conventional chemical seed treatments cannot be used, seed survival was lower averaging 83%. Seed survival was lowest at 68% during 2008, while seed survival was highest at 91% during 2009, 2014 and 2018.
Within the UW Corn Hybrid Evaluation program we have tested over 200 unique seed treatment combinations. However, there is no strong trend for seed survival improvement over time in the traditional trials, while there seems to be some improvement in the organic trials.
Joe Lauer is a corn agronomist for University of Wisconsin-Madison. Follow his blog at http://wisccorn.blogspot.com/2019/