"Will my corn make it?"
That's a question being asked increasingly in the northern half of Wisconsin's major corn growing area as the end of July arrived with much of that corn still as much as two to three weeks from tasseling and silking because of late planting and slow development.
"Make it" means reaching the blacklayer growth stage or physiological maturity of the kernels. Putting a timetable to whether that will happen was the subject for Extension Service corn agronomist Joe Lauer at the 2014 summer twilight meeting of the Fond du Lac and Dodge County Corn Growers Association.
Not only were many farmers not able to plant corn during many days in May, but some of the Extension Service's trial plots was also planted exceptionally late, Lauer reported. "It was a struggle in northeast Wisconsin — almost like in 2013."
Plots in that region were not planted until after Memorial Day — about three weeks later than the usual and intended timetable, Lauer said. He commented that the plots near Valders in Manitowoc County and Coleman in Oconto County are not looking good, while those at the meeting site on the Ed Montsma farm and near Seymour in northern Outagamie County are quite a bit better.
To salvage the late planted and slow developing plots for their intended research value, 40 units of nitrogen were supplemented to replace that lost during leaching in the wake of heavy rains in early June, Lauer said. A related problem is the likelihood of shallow roots due to the excess moisture early in the growing season — a situation that's not good in light of the well below average rainfall in the central and northern parts of Wisconsin during July, he noted.
One fortunate thing about the areas where the corn is lagging in maturity is that the demand for corn silage for dairy herd feed is high in those localities. Lauer suggested that growers who have corn that faces a high risk of not reaching blacklayer consider negotiating with potential buyers to have their crop harvested for corn silage.
Unlike other crops that are harvested as forage, corn has two windows at which feed quality is quite high, Lauer noted. The first episode of that "double peak" occurs when the corn is at its tasseling stage, while second is when the kernels are at their one-half milkline.
So, in one respect, it is acceptable to plant corn very late (in July) and plan to harvest it for silage, Lauer said. But there is a downside to that idea because that corn would likely to be too high in moisture for good storage, he warned.
For the great majority of corn for which grain will be an integral part of the silage, Lauer recommended administering the "silk shake" test to learn the percentage of kernel pollination. He explained the silks that separate from a young corn ear indicate that pollination has occurred for that kernel.
There are two good reasons to do that, Lauer said. One is that it can predict what the potential grain yield is likely to be, while the second is to share that number with potential buyers of the corn for silage.
Another method to obtain that same information is to split a few ears at their blister stage — about 10 days after the silking — to count the kernels after cell division has occurred, Lauer said. Given the reserve soil moisture and prospects for temperatures in late July and early August, he wasn't expecting many problems with pollination this year on corn, which was reaching its tasseling and silking growth stage by that time.
At the Extension Service and Syngenta trial plots for corn and soybeans on the Montsma farm, only a section of one of the corn hybrids had begun to tassel by the meeting date (July 24).
Once silking and pollination have occurred, it normally takes 55 to 60 days for corn kernels to advance to physiological maturity or blacklayer, Lauer pointed out. He said that timetable applies to corn hybrids of all projected days to maturity — 90 as well as 110.
That's why the tasseling date is important and why growers ought to focus on it, Lauer said. He pointed out that the difference in rated maturity days applies to the plant development for silking and that this can be noted in one way with the 15 leaves expected on corn plants in a hybrid with a rated maturity of 90 days compared to the 21 leaves on those with a 110-day maturity.
It takes about 40 days for kernel fill to be completed — a process that's helped by cool nights in August for the sake of the respiratory health of the corn plant, Lauer explained. Once pollination has occurred, plant growth stops and all of the energy directed to the development of the kernel.
If the pollination was poor, that corn is a candidate for harvest anytime as silage, Lauer advised. For a "fair" percentage of pollination, farmers should harvest at the usual time for making silage, he added.
Provided that a freeze doesn't occur earlier than normal, "there's a lot of time left" for a good share of the 2014 corn crop to mature if the intention is to harvest it as grain, Lauer said.
With the varying types of harvest of corn that have evolved, Lauer outlined a calendar sequence for what dates to shoot for. They are based on a normal pattern for the corn's development and maturity.
That calendar suggests about a Sept. 14 date for making corn silage or harvesting shredlage. The next date is Sept. 26 for earlage, toplage, snaplage and high moisture shelled corn with a harvest of grain bottomlage suitable around Oct. 17.
As the growing season proceeds, updates on corn crop management will be posted at corn.agronomy.wisc.edu.