A Recipe for Crop Success

Sunday, October 9, 2022

Keys to achieving a bin-busting corn crop in 2022

by Becky Dumais

"We need to have lots of kernels and we need to make them all heavy."

That's how David Hooker describes a great year for Ontario corn producers.

Hooker is a field crop agronomist and associate professor at the University of Guelph (UofG), Ridgetown Campus, and he says yield potential is excellent again this year.

So what are the current best practices to ensure those cobs are crammed with heavy kernels?

Resistance & hybrid selection

The critical phase for kernels is those two weeks before and the two weeks after silking. "The potential seed weight is set up shortly after fertilization and two weeks after silking," he explains. "That's when the potential seed weight is determined."

Prolong the grain fill period as long as possible, Hooker says; keeping the photosynthetic active leaf area as long as possible into the fall is important. "That can be done by choosing a hybrid that's a full maturity hybrid to take advantage of the growing season and also protecting the leaves against any foliar leaf diseases. We need to manage for resistance because as soon as that resistance occurs you can't go back."

Achieving a good yield depends on the hybrid, according to Jonathan Zettler, Ontario CCA. "The two biggest things are later season nitrogen applications to supply enough nitrogen to fill, and the other piece is – especially with tar spot and other leaf diseases – fungicide applications to maintain green leaf tissue."

Each producer may have their own considerations when they're selecting a hybrid, including what disease pressures they may have had, insect pressure, what herbicides they want to use ... and lastly, a genetic influence on kernel weight.

"Hybrid selection makes a difference," says Patrick Lynch, Ontario CCA and agrologist.

"However, kernel weight is not the top priority when you select a hybrid." Low DON (Vomitoxin) levels are important. "That's such a critical thing for corn producers."

Mother/nature calls

Beefing up those kernels can be done with the proper amount of moisture. "The recipe is fairly simple: if you have rain, if you have moisture, you get heavy kernels. If you don't, you don't," says Lynch.

Zettler says a determinant of corn yields is rainfall is around tasseling; solar radiation is another factor, which he cites from a dissertation written by Caleb Niemeyer for the UofG's Department of Plant Agriculture in 2020.

Niemeyer states the total rainfall during the period before silking was correlated with delta yield, the Maximum Economic Rate of Nitrogen (MERN), and yield at MERN.

"An important yield component in corn is kernel number per ear," Niemeyer writes. "It has been well documented that crop growth rate during the period bracketing silking determines kernel number and is influenced by both moisture ... and solar radiation.

"Soil moisture and solar radiation during this period are major determinants of yield and crop N requirement since these factors are typically associated with crop growth rates."

If the weather isn't co-operating, Lynch says another thing to help yield is to build up as much organic matter as possible to help with moisture and manage the crops properly after the first-year corn. Lynch says following the crop's first year, "you have a plethora of things that work away on the roots that make it hard to take up available moisture."

Areas of the province that are prone to corn rootworm may experience damage from the pest chewing the roots, preventing the plants from taking up moisture, which is where crop rotation comes into play. "If you plant corn after corn there are some root diseases that prevent the plant from taking up enough nutrients," Lynch says, noting that crop rotation will also help in the long run.

Wheat: it's what's in rotation

Hooker values crop rotation – specifically wheat – as a way to achieve higher yields.

"Wheat provides many qualities and soil benefits," says Hooker. "It has a fibrous root system and it increases aggregate stability, soil structure, and wheat adds organic matter to the soil as well. Those factors build resilience into the soil, which provides higher yields."

Lynch agrees, acknowledging the research done by Terry Daynard, former UofG crop science professor and associate dean. "(It) showed that winter wheat in the rotation increases yield. Winter wheat, with red clover, increases it even more. And with the price of nitrogen going way up, red clover and winter wheat is an absolute no-brainer."

Zettler says that rotation will impact the crop, but only indirectly. For instance, if there is increased pressure from insect or leaf diseases. If this occurs, "the plant maybe isn't as healthy because of those things and typically you need more inputs to maintain your yield."

Fertility, compaction & weeds

Lynch points out that "you can only do so much with fertility, and sometimes when people get into problems they put on more fertilizer but that won't solve the problem.

"If the root system has been compromised through diseases or insects, or compaction, the nutrients are there but the plant still cannot take it up because things like nitrogen and potash – they must get into the soil moisture to move into the plant."

A restrictive root system means the plants won't get enough moisture. "I don't care how much fertilizer you put on, it's not going to work."

Lynch also mentions soil compaction, controlled traffic, and avoid work- ing the ground when it's wet. Essentially, he says it's about good, basic crop management and "about timely planting to get the plant off to a good start."

Something else Lynch stresses is weed control. He mentions the research done by Peter Sikkema at UofG Ridgetown Campus, which shows a yield decrease if weeds aren't kept in check. "The weeds take moisture – we're trying to keep moisture to get the kernel weight. Well, if the weed's got it, the corn doesn't," he says.

Fungicide use is important. Certain types, which stay on the plant longer, "allow the plant more time to pack more nutrients into the kernel."

Field density

Optimizing plant population density promotes a good crop. "We can do that by choosing a density or plant population that's within the range of the hybrid that we choose," Hooker says.

"Seed companies know their hybrids the best, but producers know their fields the best. Within that range the seed companies provide, if the soil conditions or if the land area or a portion of the field is susceptible to drought or some other stress, then the producers should err on the side of caution and plant at a lower density."

The opposite is true for highly-productive areas in the field – where density can be increased. "The trick for high yields is to optimize each component as they occur," Hooker explains.

"The later we focus on these components – the first one being plant density, second is seed number per plant, and the third seed weight – we need to optimize each component using best management practices as those components appear in the growing season. If we leave our best management until the last component, we won't get the highest yields."

Lynch agrees density helps achieve those weighty kernels, however, too high a plant population can decrease yield and certainly decrease kernel weight.

"The real secret to this (and something very few farmers do) is variable planting rates." Take advantage of the productive areas of the field and plant less in the knolls and droughty areas that he says never yield well, dropping the population and saving seed.

What's in store for this year's crop?

Hooker says the yield potential is excellent. "Moisture conditions are excellent. We don't suffer from a lack of moisture here as in the Prairies. And there's still lots of time to get rid of the excess moisture for the timely planting of corn." BF