If you are waiting for the ground to dry enough so you can finish planting corn, Iowa State University Extension field agronomist Mark Johnson says you should consider skipping the preplant nitrogen application—if that's how you normally would apply N for corn. Once the corn is planted you can come back and apply any needed nitrogen as a sidedress application. Johnson, who covers central Iowa for ISU, offers the following tips aimed at farmers who still have some corn and beans to get into the ground.
"Another helpful hint is to be sure to continue to limit your speed when planting," he says. "Whereas 5 mph was preferable earlier, with 5.5 being the maximum suggested planting speed, you may want to consider going 5.5 mph now, with 6 mph being the maximum. Remember, speed hurts in 3 ways when you are planting corn."
The faster you plant: 1) The less accurate the seed drop; you'll get more doubles and skips. 2) You'll also get more kernel roll; and less even spacing. 3) The more row unit bounce you have as the planter moves across the field, the less even the planting depth will be, and you will see less even emergence of the corn crop. These symptoms really show up when you drive the planter across the field at more than 6.0 mph, says Johnson.
When you get to May 25, consider switching corn maturities
"If we get to May 25 and you haven't completed planting your corn at that time, you should consider switching to corn hybrids that are about 5 days shorter in relative maturity for your particular area of the state," says Johnson.
When choosing your nitrogen rate per acre to apply for corn--whether you are sidedressing or still applying some N preplant—remember you want to increase your economic return, not simply add yield. The N-Rate Calculator helps you determine that N application rate. "This is a very helpful tool, because with N rate, there is a higher rate of return per pound of N that is applied initially. And then you get much lower rates of return at higher N application rates. Once you reach the optimum economic rate of N to apply for your fields and farming situation, keep in mind that any additional pounds of N you apply will cost more than they will return in additional yield," he says.
Past May 25, if you're still planting beans, heed this advice
When you move past May 25 and you are still planting soybeans, and especially if you are still planting beans in June, consider increasing the seeding rate per acre, says Johnson. He says you should aim for a higher plant population for beans than you would normally plant. Also, decreasing the row spacing to 15 inch rows or less will help maximize your yield potential with late planting of soybeans. For example, if you've been planting with a 30-inch row spacing planter, now you should consider planting each field twice, by going cross-row, diagonal or parallel to first planting (each pass would be at half the seeding rate per acre, so you will end up with a full seeding rate). You could also consider using a grain drill if one is available.
Johnson adds, "Stay with your same maturity group for soybeans at your location—at least for now. When we get to June 20, growers in northern Iowa and central Iowa should switch to a shorter maturity group soybean variety. You should shorten it by .5 or 1.0 in the maturity rating."
What about replanting soybeans—advice for making that decision?
"Often the best decision when faced with poor or disappointing soybean stands is to do nothing," says Johnson. "Soybeans have tremendous ability to compensate for reduced stands. Up until mid-June, you should keep a stand of 70,000 soybean plants per acre. After that, a stand of even 50,000 to 60,000 plants at that time of year is worth keeping. There may be some yield loss, but the yield loss from late planting (if you decided to replant a disappointing stand) will probably be greater. Hopefully, no one in our central Iowa area will face that decision this year."
He is also getting some questions about corn seedling diseases. Alison Robertson, ISU Extension plant pathologist ([email protected]) is studying corn seed and seedling diseases. If you encounter fields with seedling disease problems, please contact Alison or your area ISU Extension field agronomist. Samples of diseased crop plant material will greatly help with this study, and the study will provide valuable information to help farmers make future management decisions."