What are your most expensive inputs for raising corn in 2015? Seed is probably near the top of the list. Can you cut seed cost by lowering population without forfeiting profit? Often the answer depends upon whom you trust for information.
Bob Nielsen prefers talking about harvest population. “We’ve found in our on-farm, replicated trials that the ideal harvest population for maximum yield is around 31,400 plants per acre,” he says. Nielsen is the Purdue University Extension corn specialist.
That puts seeding rate somewhere around 33,000 to 34,000 seeds per acre, depending upon how successful you are at achieving good stands.
There is one caveat. If you’re planting on marginal or sandy, dryland soils, you’ll need to back off on population, Nielsen says.
Economic seeding rate
The ideal economic population will be different, Nielsen says. He estimates it would be at least 2,000 plants per acre less. That puts it around 29,400, and would put seeding rate at about 31,000, depending upon your planting techniques.
“It’s going to be lower than the rate to achieve maximum yield,” Nielsen says. “Even if corn jumped back to $4.50 per bushel, the ideal economic harvest population would be lower.”
One question always arises: Do different hybrids have a different sweet spot for ideal population for top yield? Many companies say yes. So far, Nielsen hasn’t seen it in on-farm trials.
“We hardly ever pick up a response for hybrid by population,” he says.
If you’re working with a company that recommends planting various hybrids at different populations, ask to see the data behind the recommendations. Are trials replicated? At more than one site? Over multiple years?
Dollars and cents
Select the population you feel will net the most profit, Nielsen says. “Some people get nervous at harvest populations below 30,000 plants per acre,” he says. “You must make that call.”
Look at the table that represents seed cost per acre based on seeding rate and actual cost of seed per 1,000 kernels. This is based on per-bag cost after all discounts.
Note seed cost per acre varies from $84 to $108 from 28,000 to 36,000 kernels per acre if you buy seed at $250 per bag.
Now look at the second table. It depicts how many bushels it takes to recover extra seed costs compared to a cheaper choice. It also shows how the number of extra bushels needed depends upon corn price.
This table shows how many more bushels per acre you need to break even if you spend from $10 to $60 per acre more on seed.
The difference in seed cost may be due to either choosing a less expensive product, planting at a lower population, or both. As corn price increases, the number of extra bushels needed decreases.
Help for choosing hybrids
Where can you get third-party information on how hybrids within a company and between companies compare? Phil DeVillez says one place is your state land-grant college’s crop performance testing program. He heads up Purdue University’s testing program in Indiana.
If you want to find information about 2014 trial results in your state, one easy way is to visit ucta.org. It’s the website for the University Crop Testing Alliance. The U.S. map is live. Click on your state to visit your local university’s crop testing program.
“We meet once a year to compare notes,” DeVillez says. The site doesn’t contain combined data across all states simply because it would require an enormous workload, he says.
If you live in the eastern Corn Belt, visit Purdue’s site and find multistate information for hybrids and varieties tested in Illinois, Ohio, Michigan and Indiana. Visit: ag.purdue.edu/agry/PCPP/Pages/default.aspx.
These testing programs are voluntary. Companies pay to enter a hybrid. The company chooses which hybrids to enter. Sometimes a company, even a large company, may elect not to participate.
“If you don’t find your favorite hybrid included in trials near you, ask your seed rep why they don’t participate,” DeVillez suggests.
The value of university trials is that data is replicated, DeVillez says. That means results can be analyzed statistically to determine which hybrids or varieties are truly different.
The more variability in the plot, the more difference it takes between hybrids before they’re statistically different. Results are typically compared at the least significant difference of 0.10. This means that with 90% confidence, you know if two hybrids are truly different or if yield differences could be due to experimental error.
For example, the LSD number at 0.10 in the table is 13 bushels. Hybrids which aren’t 13 bushels or more different from one another aren’t significantly different at this confidence level. You don’t know which one would top the plot if planted again.
The table contains the first 15 entries from a real university trial. Company names are replaced with letters. Note that the top seven aren’t significantly different.
- Decision Time: Production is independently produced by Penton Farm Progress and brought to you through the support of Case IH. For more information, visit caseih.com/beready.