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Low canopy temperatures hammer Mid-South wheat

Mid-South farmers trying to figure out why their wheat and corn got hammered so badly during the Easter freeze have some new information that may shed more light on what happened in their fields that weekend.

Extension grain specialists with the University of Kentucky took temperature measurements inside wheat canopies at Princeton, Ky., in the morning hours of April 6, 7, 8 and 9. Readings were taken at 1 inch and at 8 inches above the ground.

Temperatures at 8 inches above the ground or about head height dropped to 16 degrees at Princeton (which is located about 100 miles north of Jackson, Tenn., on Easter Sunday, April 8, and 18 degrees on April 9. That compared to the official low air temperatures of 19 and 26 degrees (at 5 feet above ground) for Princeton on those dates.

While temperatures may not have been as extreme deeper into the Mid-South, much of the region experienced lows below the 24 degrees and 28 degrees that would be expected to cause moderate to severe damage at the jointing (Feekes 6) and boot (Feekes 10) stages of growth for wheat.

But the problems didn't end with the low temperatures on those dates, according to University of Kentucky Extension grain crops specialists.

“Normally, we would expect to have warmer temperatures that would help corn and some of the wheat survive,” said Chad Lee, interviewed on April 13. “Instead, the forecasts are showing more cold, wet weather, which is not helping our situation.”

Air temperatures in Tennessee reportedly dropped to 18 degrees on Easter morning, putting wheat and corn producers in a quandary on what steps to take to deal with damaged crops.

University of Tennessee corn specialist Angela Thompson says little corn seed is available for replanting, and the University of Kentucky's Lee says it's highly unlikely corn growers will be able to find the same hybrid they planted initially.

“If you planted half your corn in March and have seed left, use it to replant poor stands,” says Thompson, adding that producers should consider keeping any field with a uniform stand and a minimum of 20,000 plants per acre. (That number is a judgment call depending on yield expectations for the crop.)

“It might be better to keep a uniform lower population of a solid performing hybrid than to replant with a poor quality replacement, even if it means lowering yield expectations and managing for a lower yield potential.”

Lee says one of the first things farmers affected by the freeze should do is report crop damage to their county Farm Service Agency offices. Growers have 15 days after the disaster occurrence to file a Notice of Loss under the current Noninsured Disaster Assistance Program provisions.

Producers who do not purchase NAP coverage should still file a Notice of Loss with the county FSA office in case Congress enacts a disaster assistance program to help cover their losses. “We've been in contact with state FSA officials, and they're saying producers should bring receipts to prove they planted those fields.”

Kentucky farmers had planted nearly a fourth of their crop or about 300,000 acres of corn before Easter, according to the USDA's National Agricultural Statistics Service. The corn ranged from still in the ground to spiking through to plants with three to four leaves “in the other extreme.

“Any corn that was planted shallow (1 inch deep or less) appears to have been killed,” Lee noted. “The jury is still out on the remainder of the crop. The pressure for corn seed was already tight, so our farmers will face some difficult decisions.”

The recommended planting dates for western Kentucky, where the lion's share of the state's crop acres is located, run from April 1 to May 1. That's based on historical trends for such factors as soil temperatures and the last spring freeze for the area.

In Mayfield, in far western Kentucky, April 15 is the median date for the last spring frost. “So we really weren't that far off schedule for the kind of weather we've had,” said Lee.

Many farmers took advantage of the unusually warm weather in March to get a head start on planting. Although planting before April 1 is not a recommended practice, the reality, says Lee, is that growers who have planted early typically have harvested good yields.

“Unfortunately, this time the weather was very good, and it was hard to stop planting once the tractors started rolling,” he said. “There's always pressure on growers to finish planting quickly, but this year they got caught by the changing weather.”

Kentucky Extension specialists are telling corn farmers who are forced to replant that (A) they shouldn't expect to get the hybrid they want, and (B) they should find out as much as they can about the hybrid they do plant.

“Make sure you know the disease tolerance package they have,” he said. “But that really goes for the whole season. If hybrids don't rank well on dry down, for example, you should be watching for stalk rot. You may not be able to get the maturity you want, and that may affect when pollination occurs.”

Corn farmers in central and eastern Kentucky have the advantage of a recommended planting window that extends to May 15. For western Kentucky and some of the northern Mid-South, the recommended cutoff is May 1.

Some Mid-South growers may want to consider shifting to an early season corn to avoid the higher temperatures and insect problems that can plague the region's farmers in late June and July.

Growers who replant should be aware of the herbicide tolerance package of the crop they're abandoning and the hybrid they intend to plant. In recent years, Mid-South farmers have shifted to Roundup Ready corn to protect their crop from early-season, glyphosate drift.

“Freezes typically don't kill every plant,” said Lee. “Oftentimes, you have enough corn survive that you need to remove the remaining plants. Those survivors become a weed that can compete with the new crop. Tillage doesn't always help because the plant can still push up through the soil.”

If farmers plant Roundup Ready corn and plant a Roundup Ready hybrid again, it becomes difficult to kill the old corn plants. A grower might plant LibertyLink corn, instead, and use glufosinate to kill volunteer Roundup Ready corn.

Larry Steckel, University of Tennessee Extension weed scientist, has found Gramoxone Inteon at 40 to 48 ounces per acre and metribuzin at 3 ounces per acre or 0.5 pound of Lorox can provide 95 percent control of Roundup Ready corn.

A second option might be to substitute 1 pound of atrazine for the metribuzin or Lorox because metribuzin and linuron or Lorox may both be in short supply. Atrazine was not as effective on corn as metribuzin or linuron.

Growers who decide to abandon wheat and plant corn can apply atrazine plus Gramoxone Inteon or glyphosate to destroy what's left of the wheat, says Steckel. If the farmer plants cotton or soybeans, glyphosate will remove plants that have foliage that can take up the herbicide. A follow-up application of Gramoxone may be required.

“To control re-tillering wheat, plants should have about 4 inches of actively growing vegetation to allow for optimum uptake of foliar-applied burndown herbicides such as glyphosate or paraquat,” said James R. Martin, Extension weed control specialist at Kentucky. “However, many of the damaged wheat tillers will not die back to allow for new tillers to emerge quickly.”

Kentucky weed scientists also recommend growers check the labels on wheat herbicides to determine the rotational intervals for the following crop. The Harmony Extra label, for example, has been revised to allow a 14-day interval for corn and soybeans.

If growers elect to keep the crop they started with, they should protect the crop from further stress by providing adequate fertility and timely weed control, according to Thompson.

“Hopefully, Mother Nature will send the rain,” she said. “From everything I've read, the smaller the corn at time of freeze the less likely there will be a yield impact later on. Right now, I just want to see corn out of the ground again and we can ponder this more as the season progresses.”

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