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 IA, IL, IN, MN, and WI have increased plant population at the rate of 261 to 309 plants/A*yr (USDA-NASS, click here). 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 (USDA-ERS, click here). 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 (click here). This article 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% (Figure 1), 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.
|Figure 1. Corn seed survival across years in traditional and organic cropping systems. Data are derived from UW Corn Hybrid Performance Trials conducted between 2008 and 2018 (N= 12,036 plots).|
Table 1. Corn seed survival in traditional trials across locations and production zones in Wisconsin. Data are derived from UW Corn Hybrid Performance Trials from 2007 to 2018 (N= 12,036 plots).
The choice of seed company also had a significant effect on seed survival. In the traditional trials, one company had a seed survival rate of 82%, while another company had a survival rate of 97% for a range of 15% (data not shown). In the organic trials, one organic seed company had a seed survival rate of 72%, while another averaged 86% for a range of 14% among companies. This range in company performance is likely due to choice of seed treatment and seed quality effects.
There are numerous factors that influence corn seed survival including hybrid, soil type, seed treatment, tillage system, cropping system, planting date, and environment. Traditionally, we have used a survival rate of 90%. More recent data indicates that 90 to 92% is a reasonable survival rate. However, seed survival at some locations and years can be as high as 95% and would need to be taken into account in order to achieve the target plant density.