Corn isn’t just about crop heat units

New shorter-season hybrids are just part of the Prairie corn picture. Just as important will be the local research to fine-tune how they’ll fit into the production system

As the life-science companies begin to deliver on their promise of shorter-season corn for the Prairies, another challenge arises.

Typically corn is grown in rotation with soybeans in a far wetter climate in a corn-soybean rotation. How will it fit in a drier landscape, and in rotation with wheat, pulses and canola? There aren’t many row crop options in the West, so growers will need to figure out how to include corn in minimum-tillage systems.

Some changes will be obvious but others will be subtle and harder to quantify, says a researcher heading up a major research effort at the University of Manitoba.

“We know from experience that whenever you grow a new crop in an area, this kind of basic agronomic research also needs to be there,” Yvonne Lawley told Country Guide. “We’re working on pulling together the agronomy package to go with the seed package.”

Lawley is lead researcher in a multidisciplinary project that includes soil science and fertility, agro-meteorology, plant science and even the economics of corn production for the region. Funding agencies include the Manitoba Corn Growers Association, the Western Grain Research Foundation, and the Manitoba and federal governments through the Growing Forward II program.

“We’ve also benefited from some funding through Western Economic Diversification and MCGA to purchase row crop equipment,” Lawley said.

This is perhaps the best indication of where the basic foundation of agronomic research for this crop currently sits — even the most basic research infrastructure was lacking until recently.


Just where corn is going to fit into Prairie crop rotations is a big question. It fits well with soybeans in the U.S. Midwest and in Manitoba’s Red River Valley, but how will it fit with canola?

Corn needs lots of phosphorus, and relies on a symbiotic relationship with mychorrhizal soil fungi, which function like a conveyor belt transporting nutrients to the roots. Lawley says the plants need the fungi to get enough nutrition to thrive, especially in the early part of the growing season. Canola, on the other hand, is non-mychorrhizal, which means reduced fungi populations in the season following canola.

“In the first corn crop following a canola crop, there appears to be an effect on the maturity,” Lawley said, adding that other issues will probably be identified. For example, corn will be seeded into colder soils than it’s typically sown into, and that will probably have some effect on its early development. But until a few seasons of research work are done, knowing all the effects will just be guesswork.

Other major challenges will include residue management for corn, which produces an enormous amount of biomass relative to cereals, and how to incorporate the crop into conservation-tillage systems.

University of Manitoba soil scientist Don Flaten, along with grad student Magda Rogalsky, is looking at this question, along with other soil- and fertility-management strategies. Flaten says after just one year of field trials, one reassuring trend has appeared. It would seem that strip tillage — the practice of disturbing only the row that’s being planted into and leaving the rest of the field untilled — doesn’t appear to have a statistically significant effect on plant growth or yield.

“Often when you’re talking about research, getting no result is disappointing, but in this case I think for most people no news is good news,” Flaten said. “It suggests that farmers will be able to grow corn without totally abandoning all the benefits of zero tillage and minimum tillage.”

“Growth hangover”

University of Manitoba agro-meteorologist Paul Bullock is working on the climatic questions arising from bringing corn into a new environment that it’s not by nature suited to.

Corn is a long-season crop that normally likes more heat and moisture than are typically available on the Prairies. The plant also uses a different type of photosynthesis called C4, which allows the plant to continue the process in the dark.

“C4 photosynthesis is more efficient and generally results in more robust plants with higher biomass and grain yield, but it requires generally warmer temperatures to work,” Bullock said.

Corn heat units from May 15 to September 30, 2015. While the 2300-plus areas suggest enough total heat for corn, cooler nighttime temperatures may negate some of the daytime warmth.

Corn heat units from May 15 to September 30, 2015. While the 2300-plus areas suggest enough total heat for corn, cooler nighttime temperatures may negate some of the daytime warmth.

As newer and better hybrids are being developed, the crop is pushing into non-traditional areas. Research is needed into how well they adapt, and how risky they will be for farmers, which may not be measured in the traditional way.

“The basic unit of measurement for corn adaptation, one that’s been used for decades now, is the corn heat unit or CHU,” Bullock said. “It was developed years ago in Ontario, where they don’t have the same sort of cold overnight temperatures we do, which can upset a tropical plant and cause what’s known as a ‘growth hangover.’”

Anecdotal reports suggest a cold night could potentially disrupt the plant’s growth for up to three days after temperatures rebound. Bullock’s research will attempt to quantify this, giving growers a better understanding of how they can use CHUs to determine the risk of growing the crop.

Much of the fieldwork by graduate student Justice Zandah, a Zimbabwean with a lot of experience with the crop, has shown a significant variability in how the crops mature. He and technicians planted the same hybrids at seven sites — five in southern Manitoba and two in southern Alberta — and found as much as a month difference in their maturity dates.

That might in part be down to differences in the growing season, but when the weather data, generated on-site by carefully calibrated weather stations, was compared there was also a difference in maturity when compared to heat units of up to 500 CHU.

“What we found was there was a central point that represented the hybrid well, but then there was a 200 to 250 CHU variation on either side,” Bullock said. “What caused that, we’re not exactly sure, but it could be related to available moisture, as one of the sites was under irrigation in southern Alberta and the other was a dry site at Roblin (Manitoba), which also raises the question whether that meant clearer, and cooler, nights.”

It will be several seasons before any reliable results are available, but this early data does suggest there may be some pattern at work that needs to be fully understood.

Fertility questions

Flaten and Rogalsky are also looking at a few fertility questions that need to be answered for corn on the Prairies.

They’re comparing an unfertilized check against 27-pound and 54-pound per acre phosphorus applications. Both rates are made as a side band (2″ x 2″) in the spring, and also deep banded in the fall at about 5″ in depth. All of the treatments are sown into both conventional and strip-tillage plots. A similar study is testing phosphorus and zinc at the same rates, but on canola and soybean stubble, respectively.

“We can see a difference between the check and the starter phosphorus, especially in the plots on canola stubble,” Rogalsky said.

The differences were especially pronounced early in the season, with developmental differences of one to three days observed in the field. By harvest time, however, the effect had virtually disappeared, suggesting it’s going to be especially important in the event of an early frost.

“Last year was an open fall, so it does make you wonder what that would look like in a different growing season,” Flaten said. “It really emphasizes that we’re at the very early stages of this research.”

This article first appeared in the January 2016 issue of the Corn Guide

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