Mitigating effects of weather in corn
Farmers have plenty of stress to deal with – input costs, prices for their goods, pests and weather, one of the most influential effects on their income. To address weather challenges, Alex Lindsey, corn physiologist in Ohio State’s Department of Horticulture & Crop Science, presented “Managing Corn to Deal with Weather Stressors In-Season” as part of Corn Congress, recently hosted by CCE’s Northwest New York Dairy, Livestock & Field Crops Program.
Lindsey said strong storm frequency, along with season length, are two main factors affecting growing corn in the Midwest and Northeast. Warmer temperatures have led to an earlier frost-free date, with temperatures above freezing in the daytime yet still cold and lower than 50º F.
“We’re seeing declining days suitable for fieldwork,” Lindsey said.
Farmers settling for “okay” days and marginal conditions can lead to stress for a stand of corn, as colder temperatures, rain or a combination of the two is less than idea for corn to thrive.
Stormy weather and its aftermath also negatively affect corn. Lindsey said frontal boundaries bringing colder temps, along with flooding and waterlogging, hail and wind, are conditions that reduce yields.
Farmers need to assess the effects of these events by analyzing:
• How bad is it?
• What can be done?
• Could I have acted differently? The soil also matters, as planting in marginal soil will decrease yields.
“Wet soil leads to sidewall compaction,” Lindsey said. “You risk sealing rain to cause soil crusting, which may be the greatest problem of concern in heavier soils.”
Colder temperatures after planting affect yield also. Lindsey parsed out the differences between imbibitional chilling vs. cold injury.
“Imbibitional chilling is when cold water is absorbed by the seed,” he said. “Damage occurs within 24 to 48 hours of planting. The exact temperature range isn’t well known. It occurs when temperatures are below 40º.”
Cold injury happens after imbibition during emergence, when the seed is exposed to temps below 46º for extended time. It’s not clear what brief exposure periods would do.
“The result is similar – uneven emergence and poor stand,” Lindsey said.
The best way to remedy cold temperatures is to stagger planting dates. Planting all at once gambles at stakes far too high if a cold snap kills the seeds. It’s vital to avoid temperatures that are 46º or below during emergence.
“Consider phosphorus starter if cold conditions are expected and you have lower fertility soil,” Lindsey suggested. This improves early season growth and yield.
He also said to consider planting soybeans first. Wait for early planted fields to emerge. Farmers need about 180 growing degree days to obtain 90% emergence.
“Watch for changes due to pathogen losses and consider replanting if there are severe reductions,” Lindsey said.
Cold after emergence can also kill tissue, even if exposure is brief. Just two hours at 21º killed 50% of emerged plants, as did 48 hours at 28º, in his research plots.
The temperature of the tissue is what’s important, not the air temperature. A frost above ground doesn’t necessarily mean the part below the ground is dead. But tassel formation and anthesis can be shorter with early cold snaps.
It may be tempting to snip off cold-damaged plant tissue, but Lindsey said to leave it. “It looks bad, but most of the time, it won’t affect yield,” he said. “Even if it’s 55% to 70% damage seen at V4, the recommendation is to let it go. The plants will overcome lower leaf damage.”
To help mitigate the effects of cold temperatures, Lindsey is testing treating soil with biologicals, Pseudomonas aureofaciens or Pythium ultimum. Treatment of brassinolide (the most biologically active, naturally occurring plant hormone) is also under study. Initial testing showed reduced cold damage in corn seedlings at 43º.
“The bigger concern is going to be limited herbicide efficacy at cold temperatures,” Lindsey said.
Slower canopy development allows weeds to get established, which results in greater nutrient competition early, along with difficulty in the corn plants completing closure.
Flooding and waterlogging can also affect corn growing efforts. Interestingly, flooding accompanied by temperatures of 80º or higher causes greater magnitude of stand loss.
“Alleviating standing surface water and crusting is key post-planting,” Lindsey said. A rotary hoe may help break up crusting. Replanting on the shallowest depth can also help.
Seed selection matters too. “Hybrids emerge at 90%-plus, unless temperatures are too high,” Lindsey noted. “You’ll find seeds and they’ll swell up, but they’ll be killed off.”
Cooler temperatures were less damaging during flooding, with 40% to 50% emergence at 68º and 0% to 10% emergence above 80º.
“Flooding causes nitrogen loss,” Lindsey said. “Applying pre-plant before flooding [makes it] prone to loss … Delay nitrogen application until post-flooding.”
Post-flood response to nitrogen was found to have the same response rate as non-flooded conditions.
Lindsey encouraged farmers to assess drainage and surface crusting. In temperatures cooler than 60º before emergence, surface tillage may work, but if it’s warmer (68º or higher), seeds will probably die if exposed to these conditions for 48 hours or longer.
Hail damage can be devastating to corn crops. About half of all hailstorms in the U.S. occur between March and May, with another 33% between June and September. Staggering planting dates can help protect farmers against hail loss, as the crop will be in different stages when it’s “hail season.”
“Assess the damage at least seven days after the storm,” Lindsey said. Look for yield losses from stand reduction and yield losses from leaf losses.
Foliar fungicide offered limited benefit if there’s low disease pressure. Lindsey’s team’s current work focuses on defoliations, but it’s unclear how interactions of stresses and stem bruising contribute.
Wind damage can also take its toll. Root lodging and mid-season into the reproductive stages, farmers may see partial root mass removal from soil with the stem intact and plants tipping over. If recovery will happen, it occurs within three days. The yield losses are greatest near pollination and in the early grain fill stages, with 25% to 40% losses.
Wind can also cause “willowed” corn, a newer term for lodging. The stem remains intact and the plant bends. There’s limited to no recovery.
“We have very little information on yield loss from this,” Lindsey said. With greensnap, “the stalk breaks completely, but it’s not as common in New York.”
Increasing seeding rates causes minimal effect on incidence of greensnap. Choosing hybrids based on good ratings and short stature varieties can help prevent lodging and wind damage.
“Strong storms can cause damage,” Lindsey said. “Severity depends upon the stage of the corn. In many cases, it looks worse than what it is. Yield losses often ranged from 5% to 25%. We have a limited ability to simulate true stress conditions … Much of the research was conducted prior to 1995 and new tools need to be evaluated more robustly.”
