With wet spring conditions throughout a large swath of the Midwest, early corn planting hasn’t been an option for many. But once conditions dry out and warm up, corn growers will be looking to plant. If you’ve already got your corn in, or plant to plant soon- ensure that you’re doing all you can to get a good stand. We have tips from the University of Minnesota Extension, commonly asked questions and tables to help you calculate corn populations and yields.
Secrets to a Good Stand
Getting a good corn stand is essential if you want to maximize yields and profitability. Soil conditions, date, depth, temperature and rate all make a difference. Jeff Coulter, a corn agronomist from the University of Minnesota Extension provided a list of guidelines that can help maximize your net returns. The list was published on AgFax.
- Soil Condition. When soils are wet, don’t preplant till or plant. You know your field is ready to prep when soil in the tillage crumbles when squeezed. Tilling in wet soil makes clods, which can reduce your seed-to-soil contact later. Tilling wet ground can also compact the layer below the tillage and prevent good root development. Don’t do any more preplant tillage than is necessary. Too much and it will reduce moisture in the seed zone and can lead to crusting of the surface in heavy rain. All of this can restrict corn when emerging.
- Temperature. Soil temperature in the seed zone should be above 50 degrees Fahrenheit. Weather needs to remain warm.
- Date. For maximum yields, in Minnesota, corn is typically planted in late April or early May.
- Depth. In Minnesota, a planting depth of 2 inches is ideal for corn. Too shallow can mean poor root establishment. Planting at a fast speed can cause the planter to bounce, which can lead to uneven depths.
- Rate. For corn in Minnesota, the optimal planting rate is 34,000 to 36,000 seeds per acre. A greater planting rate may not impact yields, but will impact net returns. This number may vary somewhat depending on the hybrid, soil productivity, expected yield, and other factors.
Weather patterns over the past couple of springs haven’t been very conducive to early corn planting due to excessive moisture. This is the case with many areas in the Midwest- especially this year. Many farmers are struggling to get their corn planted, or struggling to get a good stand. Replanting decisions will be on the table for a large number of corn growers.
Jason Kelley, Extension Wheat and Feed Grains Agronomist at the University of Arkansas Extension provided a list of common questions he’s getting right now, and the advice he’s been giving.
Why didn’t I get a better stand?
Kelly says that if you’re planting in cooler temperatures (50 degrees) and then get a lot of rain, it’s likely that your corn seeds are having multiple issues going into the germination process. Wet soil can be anaerobic and oxygen may be limited, which can damage the seeds. This can make the seed to appear like they haven’t germinated, even though they may have been planted for 14-21 days. The seeds are likely dead or could just emerge later.
What population would you consider replanting?
In irrigated fields, 32,000 to 34,000 plants per acre. Populations that are less than 25,000 plants per acre and aren’t uniform are candidates. Populations between 26,000 and 28,000 plants per acre may be worth keeping, as the cost of replanting might be greater than what you gain by keeping it.
Also factor in the planting date. As long as you can get it done by late April or early May (in Arkansas), you should be good. If you plan to go that route, be certain that you destroy the old stand completely, as it will compete with your replants.
How late can I plant and still get maximum yields?
In Arkansas, for corn, this date is between April 25-30. This date will depend on your location.
Terry Basol of Wallaces Farmer says it’s important to look at your yield potential and the cost of replanting if you don’t get a good stand the first time around. You should be scouting your fields three or four weeks after planting. Every year there are probably areas of your fields that you might question- it’s not uncommon. How can you decide whether or not to replant?
The first thing that you need to do is to calculate your corn population. You can do this by referring to Table 1- count the number of plants in a row and multiply by 1,000 to determine the population per acre.
Do these calculations in at least six different areas of your fields. Increase your accuracy by honest assessment. Don’t leave out areas that have gaps.
There are two common reasons that grown growers consider replanting. First, you may have non-uniform emergence. If plant populations are reasonable, it’s not usually advisable to replant these areas. However, if half of your plants are two leaves behind the growth stage of the rest of the plants in your field, your yields could be reduced 5-10%.
If several 4- to 6-foot gaps occur within the row, yields will be reduced an additional 5% relative to a uniform stand. Stand gaps of 16 to 33 inches will only reduce yield by 2%.
For a more accurate calculation tool, check the ISU Extension’s Integrated Crop Management website.
The second reason corn growers may consider replanting is if your population is low. It’s not always easy to determine why this may have occurred. Sometimes it’s necessary to dig plants out of the ground so you can take a good look at the roots. Similar to Coulter’s article above, you may want to look into a few factors.
Causes of Poor Stand
- Seed quality and viability. Check your seed tag to double check the germination ratings- they might not be as good as you thought.
- Insects. You may have cutworms, armyworms, white grubs or wireworms.
- Diseases. Sometimes diseases like seed rot, seedling blight or root rot can be caused by different fungi. The longer the seed is in the ground, the more susceptible they are to infection. Germination is slow when temperatures are below 55 degrees Fahrenheit, thus making disease more likely.
- Soil compaction and crusting. If there’s sidewall compaction or crusting, fewer seedlings may emerge.
- Soil temperatures. Cold soil can be more prevalent in no-till fields- and especially those with heavy corn residue. In addition, if the soil is cold within 48 hours of planting, this can cause imbibitional chilling, and result in a poor stand.
Once you’ve figured out your stand, you need to calculate your yields. Coulter provided Table 2, which summarizes the relationship between planting date and population.
You can also use Table 2 to calculate your potential replant yields. Don’t forget to calculate the cost of replanting- consider tillage, seed, fuel, pesticides, and labor as added costs. Fall frost may also be a factor. Talk to your seed dealer to see if there are any early-maturing hybrids are available. There may also be rebates or price reductions available.
Tables courtesy of Wallaces Farmer