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Get Frosty At Your Farm? Check Planted Seed For Damage Now

Frosty temperatures were common in much of the Corn Belt overnight, and all signs point to a cooler-than-normal midrange forecast for the region, one that doesn't inspire a lot of confidence in much early corn and soybean planting progress.

Overnight temperatures that slid to the freezing point or below aren't doing much to help soils dry out and warm up after a rainy few days earlier this month, and corn planting progress data reflect that: As of Sunday, less than 10% of the corn crop is in the ground, and next week's USDA Crop Progress report will likely show just an incremental increase, analysts say.

Yet, the planting delay isn't as much of an issue yet, as is what could be happening to the seeds already sown.

A quick look at a soil temperature map shows only the southern edge of the Corn Belt seeing temps above the 50-degree mark, one critical to the early development of planted corn. Temperatures dipped into the teens in northern parts of the Midwest, leaving some spending the morning check to see how much damage was inflicted on anything already in the ground.

If you have worries that you may have seed struggling in the ground, try conducting this quick test, advises University of Minnesota Extension agronomist Jochum Wiersma.

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"With air temperatures dropping down into the high teens overnight, I have fielded a number of calls already this morning with the question whether the earlier seeded wheat, barley, oats (or any crop for that matter) will make it, especially if the ground is frozen solid," he says. "The fastest way to tell is to dig up some seed or seedlings and place them on a wetted-down paper towel at room temperature. Within 24 hours you should see elongation of the coleoptile of the seedlings. With seed that had not germinated yet, you may have to wait another day before you see a radicle and coleoptile appear. If the seed and the germ are damaged by frost, they will turn to mush within 24 hours at room temperature. If the crop had already emerged, you can simply cut the above-ground leaf material and place the seedling on the wetted-down paper towel and wait for new growth to elongate."

That portion of the germinating seed, otherwise known as the shoot, is commonly damaged by extended contact with soils cooler than 50 degrees. That damage, along with cold stress applied to the radicle, or root, of the seed, typically will lead to swollen or aborted kernels as the rest of the crop develops.

"When temperatures remain above 50 degrees F. for the first 48 hours after planting, seeds can be expected to germinate. If the soil temperature dips below 50 degrees after the imbibition period, it usually isn't an issue as the seed will be taking in water through a slower process known as osmosis," according to a university report from University of Nebraska Extension agronomists Jim Specht and Patricio Grassini. "With cooler temperatures, germination will be delayed, but should occur."

As soils do begin to warm after the cool snap, don't be afraid to get back on track with planting, considering the weather forecast, says University of Illinois Extension agronomist and corn expert Emerson Nafziger. Yes, it's important to keep your eye on soil temperatures right now to avoid prematurely putting that seed in an environment in which it can incur a lot of damage from its surroundings, but with a warming trend expected as May begins, you might be well off by proceeding with planting plans you have in place if they don't involved planting immediately.

"For each individual field, we still need to try to plant as early as conditions allow. Even if planting a week or two later would have little effect on yield in that field that year, we need to 'start so we can finish' -- getting all fields planted by early May is a goal as we try to maximize yield potential. Might this year be an exception, with potential for harm from planting into cool soils in the last week of April, with the weather forecast indicating that temperatures may stay low for the next week? As a principle, waiting until soil is dry enough to allow planting into good seedbed and rooting (less-compacted) conditions is more important when soils are cool than when they are warm. We never want to work soils wet and plant under wet soil conditions if we can help it, but we certainly do not want to do that in April, especially when soil temperatures are less than normal," Nafziger says. 

"The chances of getting good emergence when planting into cool soils are higher if here is little or no rain between planting and emergence. Cool soils bring slow germination and emergence, but they may lower the chance of emergence problems due to soil crusting or to saturated soil. Heavy rainfall is not predicted for this coming week or so, which is a positive. Taking the longer view, temperatures in May will inevitably start to rise at some point in time, and this will speed up emergence. Taking all the factors together, I would suggest that planting proceed as long as soil conditions are good, even if the germination process will be slow due to cool soils in the near-term," he says. 

Map above courtesy Syngenta GreenCast.

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