Tropical corn hybrids may work in Upper Midwest climates as forage for dry cows and heifers. But with little research and seed availability, it"s a crop most northern farms may never see.
Unless you farm in the southeast U.S., tropical corn hybrids probably do not sound like an option for your acres. In places like Florida, tropical corn hybrids are used if planting is delayed past April, or as a second crop rotation planted in July or August. A Florida Extension publication reports that irrigated tropical corn silage will yield between 11 and 17 wet tons per acre, higher than the traditional temperate corn hybrids when planted late.
Tropical corn hybrids are more resistant to insects and diseases than temperate hybrids. But unlike traditional northern corn crops, tropical corn responds to light for growth; not temperature. At the equator, tropical corn"s origin, days have nearly 12 hours of light year-round.
When grown at northern latitudes, this results in an extended vegetative state and delayed flowering for tropical corn hybrids. The lack of grain results in more sugar in the stalk, and a high NDF forage that could be well-suited for dry cows and heifers.
Pat Hoffman, Vita Plus dairy technical specialist, mentioned the tropical corn silage as a forage alternative in his northern-climate double-cropping presentation at the company"s annual Dairy Summit last December. His presentation focused on more typical northern rotations like corn silage to winter rye or triticale, alfalfa to fall oats, rye or triticale, alfalfa to corn silage after first crop, or winter rye/triticale to sorghum Sudan grass. But the mention of tropical corn silage led to the greatest discussion after the presentation ended.
"If you plant tropical corn silage in mid-May you will not see much difference in tropical corn or regular corn before the end of July," Hoffman said of his experience with the University of Wisconsin when they were experimenting with some plots at research farms.
"Typically in late August, when the days hit 12 hours of both light and darkness, tropical corn will start to elongate, growing 12 to 14 feet tall," Hoffman added. But since tropical corn does not reproduce until after the 31st leaf, there are not enough growing degree days in northern climates to produce ears.
Cellulosic was initial idea
Hoffman saw the plants at the University of Wisconsin"s research plots near Marshfield, Wis., latitude of about 44.6667' N. With several more years" research, he thinks the northern industry could have another viable forage opportunity, especially for dry cows or heifers. But tropical corn was not brought north due to dairy cows.
Just a few degrees of latitude lower, at about 40.1097' N, researchers at the University of Illinois, were studying tropical corn with different results and a different industry in mind. There, the crops" ears developed fuller and therefore the silage contained more starch than just a few hours north in Wisconsin.
The cellulosic ethanol industry has been studying the crop for use as a biomass ingredient. There is both an ethanol-specific high sugar variety and a dual-purpose variety for either ethanol or feed for added flexibility.
In a 2013 issue of the Tropical Maize Review, Illinois Extension Educator Gary Letterly writes that baled biomass produced 5.5 tons per acre in a no-till doublecrop after wheat, while the state"s hay yields were only 4 tons per acre during the same period. When ensiled, tropical corn crude protein reached nearly 8% and a TDN over 60%.
In an Illinois beef cow study, tropical corn silage showed no difference to temperate corn silage in cow weight gain when fed at equal levels.
For the corn ethanol industry, currently the starch in corn grain is the major source for first-generation energy. Second-generation biofuel sources include corn stover, sorghum, sugarcane, switchgrass and tropical corn.
But the University of Illinois reports that only sugarcane, sweet sorghum and tropical corn can provide all three options for feedstocks; sugar, starch and lignocellulosic biomass. And, of those three options, tropical corn has the broadest geographic production range, the greatest genetic resources, and is the most familiar to U.S. farmers" agronomy practices.
Tropical corn also has low start-up costs, no long-term commitment, little change in equipment, and a favorable risk-to-profit ratio compared to other options, according to the University of Illinois report.
University of Illinois researchers recommend that a dual purpose variety could provide the producers the most flexibility. It would provide a low starch high NDF forage yielding or 6 to 7 tons per acre of dry weight for thermal or forage use, but the potential is still years away.
Not ready yet
But Pat Hoffman warned that it is not something you should jump right into.
"We have a lot to learn," Hoffman warned immediately after suggesting it could be a great crop. "If you can get the seed, try a little bit first. No one knows how this might work in your area."
Researchers are also looking at the applications of tropical corn for ruminants in Canada, but after one year of good results, they had trouble obtaining seed due to regulatory approvals of seed treatments between South America and Ontario.
"Two years ago at the Canada"s Outdoor Farm Show we planted a very small plot and had very good success with it," said Ron Lackey, a feed ingredients and by-products feeding specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs in an interview with Dairy Herd Management. For those keeping score, the Farm Show"s latitude would be about 43.1306' N, or just south of Marshfield, Wis. "It grew 12 to 13 feet tall and looked very promising," Lackey said. "We planted some again last year, but had trouble with seed germination. But certainly, based on our first year experience, there is some potential for it – realizing we did it at a very small scale."
Lackey also said that some colleagues have interest in the high-sugar varieties that could also benefit anaerobic digesters.
As for feeding, the Canadian team did run their small plots through mini-silos to take it to feed out. Lackey saw that the sheep seemed to prefer the tropical corn silage in a trial against hemp, sorghum, and millet.
"We are moving ahead, but not too quickly because it is hard to get the seed for it," Lackey said