Corn Seeding Rate Considerations
Crop Insights written by Steve Butzen1, Agronomy Information Consultant
- Each year, DuPont Pioneer evaluates corn plant population responses in research trials that span the Corn Belt of North America.
- Growers can use the multi-year and multi-location results to identify the best potential planting rates specific to their hybrid, location, and management practices.
- In studies conducted from 2009 to 2014, the seeding rate that generated the most income ranged from about 31,000 seeds/acre at the 150 bu/acre yield level to over 39,000 seeds/acre at the 240 bu/acre yield level.
- According to a 2015 Pioneer survey regarding seeding rates on corn acres in the U.S. and Canada:
– almost 10% are now planted at 36,000+ seeds/acre – one third are planted at 33,000 to 36,000 seeds/acre – one-third are planted at 30,000 to 33,000 seeds/acre
- In challenging emergence environments, growers may need to increase rates. See seeding rate tips in this article or contact your local Pioneer sales professional for help.
Hybrid improvements in stress tolerance have led to higher populations and increased yield potential over the years. Since 1985, average corn seeding rates used by growers in the U.S. and Canada have increased by about 300 seeds/acre per year, while U.S. average yields have increased by almost 2 bu/acre per year (Figure 1).
Figure 1. Average corn seeding rates reported by growers in the U.S. and Canada (Pioneer Brand Concentration Survey, 2015), and average U.S. corn yields (USDA/NASS).
Introductions of new traits and technologies as well as continual breeding improvements may change the relationship between plant density increases and yield gains. Thus, DuPont Pioneer scientists continue to evaluate corn population responses in research trials that span the Corn Belt of North America (Figure 2).
Figure 2. DuPont Pioneer plant population test locations in North America, 2011-2015.
These studies test for complex G x E x M (genetics x environment x management) interactions, which frequently play a key role in maximizing yield potential and reducing risk. Researchers target representative environments based on maturity zone, expected yield (high or low), specific stresses (drought, pest pressure, high residue, early planting, etc.) and other unique location characteristics that could result in repeatable hybrid x population responses.
Additionally, hundreds of on-farm Pioneer® GrowingPoint® agronomy seeding rate trials are conducted each year comparing multiple corn products at up to four seeding rates at each location (Figure 3.)
Figure 3. Pioneer® GrowingPoint® agronomy on-farm seeding rate trials at 1,378 locations in North America in 2015.
Growers can use the multi-year and multi-location results to identify the best potential planting rates specific to their hybrid, location, and management practices.
Corn Seeding Rate Trends
Each year, Pioneer documents seeding rate trends by surveying farmers regarding the rates currently used on their farms (Figure 4.)
Figure 4. Distribution of reported U.S. and Canada corn seeding rates, Pioneer Brand Concentration Survey, 2015.
This survey shows that in both 2014 and 2015, the percent of corn acres planted between 33,000 and 36,000 seeds/acre was equal to the percent planted between 30,000 and 33,000 seeds/acre. Fully two-thirds of all corn acres in North America fell within those 2 ranges. Corn acres seeded above 36,000 seeds/acre continued to increase, while acres seeded below 33,000 seeds/acre continued to decrease. In Illinois and Iowa, percent of corn acres seeded above 33,000 seeds/acre was 61% and 68%, respectively (data not shown).
DuPont Pioneer corn plant population trial.
DuPont Pioneer Plant Population Research Results
Results by Field Productivity Level
Grouping locations with similar yields is a useful way to analyze plant population results because it can indicate which populations are needed for the yield levels growers intend to achieve. Like previous Pioneer studies, the current data set (2009 to 2014 trials across the U.S. and Canada) shows that the plant population required to maximize yield increases as yield level increases. Interestingly, unlike many previous results generated with older hybrids, the response curves in this study were roughly linear within the range of populations and yields represented by the data (Figure 5).
Optimum Economic Seeding Rate
As yields increase with each increment of higher seeding rate, a point is reached where the yield benefit from the next addition of seed no longer exceeds the cost of the seed. That point is the optimum economic seeding rate. By definition, it is the seeding rate that generates the most income when seed cost and grain price are factored in.
Figure 5. Corn grain yield response to seeding rate at 9 yield levels, 2009 to 2014. Dots indicate the economic optimum seeding rate within each yield level.
Economic optimum seeding rates are based on a seed cost of $3.50/1,000 seeds and corn grain price of $4.00/bu.
The results show that the economic optimum seeding rate increased from approximately 31,000 seeds/acre at the 150 bu/acre yield level to over 39,000 seeds/acre at the 240 bu/acre yield level (Figure 5.) An Iowa State University study comparing corn yield responses to plant population across soils with different corn suitability ratings found similar results (Woli et al., 2014).
Results by Hybrid Maturity
Population response of 5 comparative relative maturity (CRM) groups is shown in Figure 6. These data show a fairly similar response of hybrid maturities to plant population. However, for the earliest hybrid maturity grouping (<100 CRM), a slightly higher population optimum can be detected. Some researchers theorize that the disadvantages of smaller stature and lower leaf area index of early maturity hybrids are alleviated by higher populations. Increasing leaf area index may be required for highest yields in northern areas with limited light availability during late ear-fill stages.
Figure 6. Yield response to plant population for corn hybrids from 5 maturity (CRM) ranges, 2009 to 2014.
Seeding Rate Tips
Challenging growing environments may reduce corn plant populations below optimum levels. These conditions can occur when planting into no-till or high-residue seedbeds, or cloddy or compacted soils. Soil-borne diseases and soil insects can also diminish stands. All of these factors can interact to challenge stand establishment, and effects are magnified when planting early into cold, wet soils. Therefore, consider the following points when choosing your seeding rate:
- In general, plan to drop 5% more seeds than the target population to account for germination or seedling losses.
- Boost target seeding rates by an additional 5% for extreme or challenging environments such as those described in the paragraph above.
- In areas with perennial drought stress, seeding rate targets are lower. Base your seeding rate on the specific hybrid population response at the historical yield level of the field.
- Consult your Pioneer sales professional for optimum economic seeding rates of each Pioneer® brand hybrid, as well as hybrid placement tips and other helpful management suggestions.
- The DuPont Pioneer Planting Rate Estimator, available online and as a free mobile app, allows users to generate estimated optimum seeding rates for Pioneer brand corn products based on data from Pioneer research and Pioneer® GrowingPoint® agronomy trials.
Jeschke, M., P. Carter, P. Bax, and R. Schon. Putting variable-rate seeding to work on your farm. Crop Insights Vol. 25, No. 14. DuPont Pioneer, Johnston, Iowa.
Woli, K.P., C.L. Burras, L.J. Abendroth, and R.W. Elmore. 2014. Optimizing corn seeding rates using a field’s corn suitability rating. Agron. J. 106:1523-1532.
1 Steve Butzen, Agronomy Information Consultant, DuPont Pioneer, Johnston, Iowa.