Corn Watch: ’19 field is off and running- finally!

June 8, 2019

The big day finally arrived! The operators planting the Corn Watch ’19 field were able to plant into reasonably good soil conditions in minimum tillage on May 28. These farmers were able to plant all their corn within the next week.

The corn was up and visible nine days after planting. Even though there were a couple of cooler days with air temperature highs in the high 70’s during that stretch, quick emergence is a hallmark of later-planted corn. Soil temperatures are typically warmer, Dave Nanda, SGD director of genetics, notes.

One thing Nanda will be watching is how quickly corn develops. He notes that corn planted in very late May, like this field, should mature somewhat more rapidly than if the same hybrids had been planted four weeks earlier, or about May 1.

Field background

Two hybrids were planted with a 24-row planter, creating blocks of 24 rows of each hybrid across the field. The operators stuck with a 112-day and a 113-day hybrid in this field.

Their normal strategy is to apply anhydrous ammonia in the spring before planting. Anhydrous ammonia was injected at the rate of 180 pounds of actual nitrogen per acre on this field several weeks before planting, and before it was obvious there would be substantial planting delays. This field was also spread with 100 pounds per acre of ammonium sulfate, providing nitrogen and sulfur, although there’s no guarantee how much of the nitrogen applied in that form will still be available to plants after wet weather.

Plant development

According to the Purdue University Corn & Soybean Field Guide, in a normal year, it takes about 82 growing degree days to produce the next leaf stage, beginning at emergence through the 10-leaf stage. Planting to emergence typically requires 110-120 Growing Degree Days (a measure of the amount of energy accumulated for growth based on maximum and minimum temperatures per day).

Here’s an example based on the Guide: If corn in the Corn Watch ’19 field emerged June 5 and 600 GDDs accumulate between June 5 and July 4, this crop would be expected to be beyond the seven-leaf stage by July 4. That’s 600 divided by 82 or 7.3 leaves produced. The estimated 600 GDDs accumulating between June 5 and July 4 are based on a 40-year average for central Indiana from 1971 through 2010.

From V10 to the final leaf, agronomists have determined that corn plants typically require 50 GDDs to produce a leaf in a normal year. Between July 4 and July 25, another 500 GDDs accumulate on average in central Indiana. If these plants produce 18 leaves total, they would need 400 of that 500, and should produce final leaves somewhere around July 20.

Speed up maturity

As noted above, based on work by Purdue’s Bob Nielsen and Ohio State University’s Peter Thomison, since this is a late-planted year, not a normal year, it should take fewer GDDs to reach maturity, Nanda says. The formula the agronomists develop says on average it takes 1.6 GDDs fewer per day of delayed planting after May 1 from planting to silking.

With a 27 day-delay (May 1 to May 28), that’s nearly 44 fewer GDDs required during that period. Don’t be surprised, assuming average GDD accumulation, if this field reaches final leaf stage and silking before July 20.

The real increase in maturity comes after silking. From planting to black layer, the same hybrid planted May 28 vs. May 1 should reach black layer roughly requiring 200 fewer GDDs.

Stay tuned to #CornWatch19 see if these numbers hold true this year.

Seed Genetics Direct is the sponsor of Corn Watch ’19. Stories are written by Tom Bechman.