ISU: Don’t panic over plant delays
ISU: Don’t panic over plant delays
Hybrids can still yield well if planted this month
By LARRY KERSHNER
FORT DODGE Even though agronomy publications in the 1970s say corn should be planted no later than May 7 to assure full yields, that’s not the case in 2013.
Mark Johnson, an Iowa State University Extension field agronomist, told 28 producers and crop consultants on Wednesday at the Webster County ISU Extension office that corn hybrids can still reach a 95 percent yield if planted by May 18, and can yields reasonably well if planted later this month.
Although more rain was forecast for central Iowa on Wednesday and Thursday, Johnson said the outlook was good for fair weather for the next week, and is confident that farmers can get seed in the ground for a good yield, without switching maturities.
In a nutshell, Johnson’s hour-long presentation told farmers:
1. Don’t panic.
2. Don’t work in wet fields.
3. Don’t switch hybrids.
4. Use the least amount of tillage as possible.
5. Test fields for nitrate availability in topsoil, because 2012s N carryover and fall-applied manure may have leached away with March and April rains.
Johnson told farmers that corn planted between April 15 to May 18 has a yield potential window of 95 to 100 percent depending on soil conditions.
“Early planting and late planting,” Johnson said, “does not guarantee yields.”
He said soil moisture and temperature have more impact on early corn emergence and plant health than planting date.
Soil temperature charts showed that Webster County soil temperature was at 51 degrees on May 1, but slipped to 37 degrees by May 3 and didn’t get back over 50 degrees until Monday when it measured 53 degrees. About 5 to 8 percent of Webster County’s corn was planted before the May 1 snow storm that blanketed the county in 8 to 9 inches of wet snow. Northern tier counties got up to 13 inches.
He said what corn was planted before May 1 needs to be scouted continuously from emergence to V1 stage (with one developed leaf), to determine if a field needs to be replanted. If soil conditions were too cold for seeds, Johnson said, it will adversely affect emergence and plant health.
He said he’s inspected a few fields and found the young plants appeared to be in good shape.
However, he said, if a window opens for planting, he’d get seeds into unplanted fields before pulling the trigger for replanting.
Gene Frueh, of Barnum, said he found this advice was welcome news. He has a corn/soybean rotation and has done no field work as of Wednesday.
Johnson’s call to be patient, Frueh said, was confirmation that he had made the right decision.
Avoid wet soils
Johnson recommended that farmers be patient and check soil conditions before planting.
“Many times people get anxious and many get into the field one day too soon,” he said.
He advised checking soil moisture at planting depth and at tillage depth. “If the soil forms in a ball and tossed in the air, it’s too wet if it doesn’t break up.”
Tilling or planting in soils too wet, he said, “will create what we call a smear layer, which will be a problem for roots to penetrate.”
Smear layer is also known as sidewall compaction, which forces roots to go down in a narrow pattern, rather than radiating outward for a better stand.
“I recommend on getting by with as little tillage as you can,” Johnson said.
Johnson said some farmers are considering switching to a shorter maturity hybrid due to delayed planting.
“It’s too early to switch,” Johnson said. “Hybrids, if planted late, will shorten the time from planting to silking, while lengthening the days from silking to black layer” or full maturity to allow for more grain filling.
He said days to silking are shortened more than days are lengthened to reach physiological maturity. “Don’t switch until the end of May.”
Johnson said that tile line monitors are showing excessive rates of nitrate leaching from fields within the Boone and Raccoon watersheds.
This is due to the constant March and April rains and much of the nitrates are from the 2012 carryover from the drought and fall-applied manure.
When anhydrous ammonia is applied to fields it quickly breaks down to ammonium, which attaches to organic material and clay particles in soil.
However, microbes feeding on ammonium change the composition to plant-available nitrates, which is unstable and will either exit the soil through the air or as water moves though the field.
He said the dry 2012 fall left nitrate in the soil. In addition, fall-applied manure underwent extensive change to nitrate because the ground remained warm until late December.
Johnson expects that much of the nitrate being monitored from tile lines are from these sources.
However, he expects that any nitrogen applied after soils cooled is still present, since anaerobic action has been slight due to cool temperatures this spring.
He recommends sampling soil for nitrogen composition. But those not intending to sample, should consider limiting nitrogen applications to normal levels.
At the same time, in fields with lower amounts of infiltrating rain, he recommends cutting back from one’s normal fertilizer rate.
For those planning to test for nitrate levels, Johnson said a 25 parts per million or higher content has “little chance of additional applied N paying for itself.”
Concerning soybeans, Johnson said there is still plenty of time for planting them; that May 20 is still considered fairly early.
When asked if root worms will have hatched and starved before this year’s corn is planted, Johnson was doubtful.
“They operate on heat units (just like corn),” he said. “I don’t expect them to not be a problem.”
Johnson’s presentation was also viewed remotely in Pocahontas, Cerro Gordo, Calhoun, Hamilton, Humboldt and Wright counties.
Johnson is based out of Ankeny, serving nine central Iowa counties. He is replacing long-time ISU field agronomist John Holmes who is retiring at the end of May.
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