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A tale of 2 seasons: 2 planting dates means 2 pollination times

A tale of 2 seasons: 2 planting dates means 2 pollination times
Crop Watch: Corn pollinating at two different times may reflect difference in weather conditions.

When was the better time to pollinate this summer if you were a corn plant? Was it July 6 through July 15? Or was it between July 15 and July 30? If this sounds like a loaded question, that’s because it is!

Dave Nanda, crops consultant who works with Seed Consultants Inc., sponsor of Crop Watch ’16, would say, "It depends." Whether or not pollination will be successful generally depends on factors related to weather conditions, he notes.

2 CROPS IN 1: Most plants in the foreground haven’t tasseled yet, while some plants in the background are tasseled. The younger plants represent the second planting in this field.

Was it dry or was there plenty of moisture? Was it cooler than normal, normal or above normal on the thermometer? For both, that depends on where you farm. Crop reports from around the state of Indiana from early to late July indicated wide differences in moisture supply. One farmer in Morgan County in central Indiana reported 10 inches of rain from July 1 through July 20 — well above average.

Others reported more average totals, with still ample rainfall. One farmer in Cass County, Ind., reported just under average rainfall, but not enough below average to impact the crop, at least not at that time. Yet some in the northern fourth of Indiana and into southern Michigan and parts of Ohio said it was flat-out dry during most of that stretch.

Heat factor

The second half of the pollination equation is heat, Nanda says. While temperatures were near average through much of July, a heat wave sent them soaring across much of the area in late July.

How much high temperatures affect pollination may depend upon how much moisture is available in the soil, Nanda says.  If it’s hot but there is ample moisture, pollination is more likely to continue relatively normally than if it is hot and dry.

“We found out in 2012 what happens when it is very hot and very dry,” Nanda says. “Today’s hybrids are reasonably good at handling one or the other. But the two together can really mess up pollination.”

When it’s very hot and very dry, several things can happen. Silks may emerge late, perhaps after pollen shed has occurred. There may simply not be enough moisture for the process to occur normally. Various patterns of poor pollination on ears at harvest may result.

Crop Watch field

In this year’s Crop Watch field in the area where there is a significant number of plants from both the original planting date and a later planting date, two pollination windows occurred. The first window in early to mid-July saw the early-planted corn pollinate.

Since there was plenty of moisture and temperatures were about normal, conditions should have favored successful pollination, Nanda says.

The question mark is with the later-planted corn. There was adequate moisture in late July when it pollinated. However, it was much hotter, with temperatures for a couple days in the mid-90s and heat index numbers above 100 degrees F.

Was that hot enough to affect pollination? Did it impact plants in other ways? What signals did it send to earlier plants that were pollinated concerning grain fill? The Crop Watch ’16 field will provide the answers a bit later this year.

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