- On average, hybrids will only lose 1 bushel for every 10 days of planting delay prior to May 10.
- Planting dates after May 10 can experience up to 1 bu/day of delay yield loss.
- Yield benefits of full-season hybrids offset potential grain-drying costs, enough to discourage switching relative maturity (RM) prior to the last week of May.
- Corn hybrids mature with fewer accumulated heat units when planting is delayed, minimizing the risk of fall frost injury.
When is the best time to plant corn?
Historical Golden Harvest® Agronomy in Action research, as well as numerous university trials, have shown that there is minimal yield loss (0.11 bu/day) from delayed planting before May 10 or thereabouts. After May 10, the penalty (1 bu/day) for delayed planting is much bigger (Graph 1). Frequently, farmers consider switching to an earlier-maturity hybrid as a result of delayed planting and concerns around an early fall frost. Before considering an earlier-maturity hybrid, it is important to understand the research in order to make the most profitable decision.
Graph 1. Effect of planting date on corn yield potential.Is corn maturity delayed a day for each day planting is delayed?
Graph 2. Planting date influence on days in vegetative and reproductive stages. Agronomy in Action Research Trials 2021.A slight delay in planting does not always translate into the need to switch to a shorter relative maturity (RM) hybrid to avoid wet corn or fall frost injury. It is well understood that corn hybrids mature with fewer accumulated heat units when planting is delayed.1,2 This allows the same RM hybrid to reach physiological maturity in fewer days when planted later, reducing the risk of delayed maturity and potential frost injury. There still may be a need to switch to an earlier RM corn hybrid at some point in time. However, a 1-day delay in planting does not mean a day delay in harvest.
Agronomy In Action research trials looking at the number of days required to reach maturity (black layer) showed that planting the first week of June resulted in hybrids maturing in 10-16% fewer total days than when planted in April (Graph 2). Late planted corn hybrids advanced through vegetative growth stages more quickly at later planting dates to maintain a similar number of grain filling days and maximize yield potential. This phenomenon lessens the need to make big changes in RM when planting is delayed and still reach maturity before first frost dates.
A Central Iowa example shows the predicted black layer dates for three different RM corn hybrids planted at four different dates using the assumption that hybrids planted later than May 1 mature in approximately 6.8 fewer GDDs for every day of delay. In this example a 110RM hybrid, which is considered mid-full RM for the area reached full maturity several days prior to the normal first frost date when planted on May 30 (Graph 3).
Graph 3. Predicted corn hybrid black layer dates for 3 different RM hybrids in a Central Iowa example.Do I need to switch to earlier hybrid at later planting dates to minimize dryer cost?
Golden Harvest Agronomy in Action research has conducted multi-year studies to better understand the financial impact associated with switching to an earlier RM hybrid too soon. Looking at Graph 4, assumptions of $7.00 per bushel grain price and 10¢ per point moisture removed per bushel (down to 15.5%), drying costs along with yield and moisture data from planting date trials were used to calculate $/A return for full (green line), mid (orange line) and short (blue line) season hybrids, adapted for the area.
For the research studies and Graphs 4 and 5:
- Full-season hybrids were defined as the maximum acceptable RM for the trial area.
- Mid-season hybrids were 4-7 RM earlier than the full-season hybrids.
- Short-season hybrids were 8-11 RM earlier than full-season hybrids.
Graph 4. Effect of planting date on gross return by corn relative maturity group.In over 41 trials, the yield benefits of planting a full-season hybrid outweighed the drying costs at harvest for planting dates up to May 18. After May 23, switching from full- to mid-RM hybrids (4-7 RM earlier than maximum RM for area) may start to provide slight return advantages. Aggressive changes of 8 or more RM earlier than the maximum RM for your area may result in drier grain. However, less yield potential of earlier RM hybrids will result in lower profit than drying a fuller season hybrid. University recommendations for most Midwestern corn-producing states, such as Michigan State University, University of Minnesota, Iowa State University and University of Wisconsin support waiting until May 20-May 30 before switching to earlier RM hybrids.
Looking at Graph 5, assumptions of $4.50 per bushel grain price and 10¢ per point moisture removed per bushel (down to 15.5%), drying costs along with yield and moisture data from planting date trials were used to calculate $/A return like Graph 4 above. Data trends for changing RM is similar to Graph 4, however, based on the $4.50/bu corn price scenario, switching to an earlier RM hybrid is advisable a few days earlier. The yield benefits of planting a full-season hybrid outweighed the drying costs at harvest for planting dates up to May 15.
Graph 5. Effect of planting date on gross return by corn relative maturity group using $4.50/bu corn.There are many other reasons to consider switching to an earlier RM hybrid that also need to be considered. Lack of access to grain-drying capabilities (bu/hour), grain contract delivery dates and harvest capacity (A/day) are just a few reasons to consider switching earlier. If these factors are not a concern, you may have an opportunity to maximize your profit potential by sticking to your original hybrid selection.
If it is determined that an earlier hybrid is needed with delayed planting, selecting hybrids that are no more than 8 RM earlier than the originally selected, normal, full-season hybrid can still have good yield potential. It is important to select a locally adapted earlier RM hybrid and not just something earlier than the original hybrid. Talk to your local Golden Harvest representative to find the best choice for your field.
Switching to Soybeans
Once June 10 passes, changing corn acres to soybean acres becomes a more serious conversation. Evaluate a couple of goals as you consider the switch:
- Do you need corn to feed livestock? What are your options for silage vs. high-moisture corn?
- How important is it to keep a good crop rotation? Sometimes it comes down to planting or not getting a crop in the ground.
If you do switch to soybeans, remember that later-planted soybeans also have a few more management considerations to ensure success. The following links may be helpful if needing to plant soybeans later than desired:
For more agronomic insights or for assistance to make this decision, contact your local Golden Harvest Seed Advisor or agronomist.
1Brown, Greg A. 1999. Influence of Delayed Planting on Growing Degree Day Requirements of Corn (Zea mays L.) Hybrids During Grain Fill and Maturation. M.S. Thesis, Purdue University.
2Nielsen et al. 2002. Delayed Planting Effects on Flowering and Grain Maturation of Dent Corn.
Product performance assumes disease presence.
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