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Grain Corn Agronomy Research

Farming Smarter began to study grain corn agronomy for a southern Alberta crop quite a while ago.

This week’s Way Back Wednesday takes us to an article from our 2015 magazine where we talk about grain corn in rotations.

Corn On Deck for Rotations

Young corn plant

A steady domestic market, seeding/harvest timing and lots of upside yield potential spur annual increases in Alberta’s corn acres. Corn offers an ever-expanding line-up of herbicide tolerant and insect resistant hybrids with lower heat unit needs. But, corn, especially grain corn, is a fairly new crop to this area so there’s a lot to learn and, if you like growing it, equipment to buy.

Corn fits well and brings diversity into southern Alberta rotations. It’s not a good idea ahead of wheat because corn is highly susceptible to fusarium. Stems are mainly affected, so the disease may not be obvious, but crop residue can carry abundant inoculum to affect following wheat crops.

Corn seeded into canola stubble looks fine, but it doesn’t yield quite as well as after other crops. Corn on corn is quite common, but agronomists warn they see corn diseases more often lately.

Experts advise seeding into cultivated land or at least strip-tilled seed rows to let the soil warm and minimize compaction. Manured fields are favourites as the crop draws down high nutrient levels.

The first corn growing hurdle is to choose the right hybrid for the intended crop use. Do you want grazing, silage or grain? Do  you plan to harvest grain or store earlage? If you combine grain, will that be stored as high moisture storage or binned? Do you have access to a grain dryer?

“The rule of thumb is to target a hybrid that needs CHU (corn heat units) close to the average for your area,” says Nicole Rasmussen, southern Alberta agronomist with Pioneer. “Subtract 50 to 100 CHU if you want to bin grain corn and don’t have a dryer. Add 150 to 250 CHU to your average for silage – you don’t need the crop to reach full maturity. For grazing corn, add 175 to 275 to the CHUs for your area so the cattle will eat less mature plants and have less chance of grain overload.

“Find out the stage of maturity used in listing each hybrid’s CHU needs. Each company uses different end points for the crop. Also, ask for local data – every hybrid has a unique personality and the one you choose may have an unexpected response to your environment.”

According to Rasmussen, reasonable target yields are 130 to 160 bushels an acre grain corn and six to nine tonnes of silage (dry matter).  Getting your target yield depends on getting the crop off to a good start. Corn seed and seedlings are big but they’re not tough.

That big seed needs to imbibe quite a bit of moisture from the seedbed to start germination and it needs warmth. Adrian Moens, a Pioneer seed rep for southern Alberta says, “Seed generally from May 3 or 4 when soil temperatures are 10 C and not after the May long weekend. If the forecast includes snow or cold rain, park the planter. Corn hates to be chilled.”

Corn is very sensitive to salts from fertilizer.  Moens likes to see 5 lbs/acre of starter phosphate in the seed row, a little more if it’s in a separate furrow, with most of the P broadcast and incorporated.  You can broadcast N too, but the ideal way to put on the 180 to 200lbs N corn needs is in two or three applications through the pivot. “Even better is grey water from a lagoon,” he says. “When you spoon-feed corn like that you can hear it grow if it’s a hot day.”

Visit our YouTube Corn playlist to explore what we’ve learned over the years.

The experts prefer a corn planter with its precise placement of every seed over an air-seeder when small differences in seed numbers make a big difference to crop yields. “An air-seeder leaves skips and then puts two or three seeds in a clump,” says Moens. “I put a value of 5 cents on each corn plant, but two plants together compete, so they don’t both count. A plant that’s one leaf behind doesn’t count and one that’s two leaves behind the crop is a weed – herbicide resistant, too.”

Checking plant population is crucial according to Moens. Target populations are quite low, around 34,000 an acre for Lethbridge area.  Unlike wheat, where higher populations can speed maturity, too high a population in corn delays maturity.

Whatever seeding system you use, you have to make it easy for the seedling to develop roots and emerge. Check for sidewall compaction or furrows that aren’t well closed. Wait a day or two for the seedbed to dry out or change packer pressure. Rasmussen advises replacing at least one packer wheel with a spiked one, for wet conditions.

Corn takes a while to get out of the ground and get going. Moens calls this “developing its vitals.” If you cut a seedling open as it emerges, at the five or six leaf stage, you can see all its future organs, even the tassels. When you’re checking stages in corn, count leaf collars, rather than actual leaves. The lowest ones often disappear and include the first or thumb leaf.

The closer a corn plant is to 6 leaves, the more frost sensitive it becomes. Around this time, you may find twisted, even corkscrew plants that seem to be heading back underground. It’s not herbicide injury, it’s most likely a chilling effect. A cool night, cold rain or irrigation water is enough to chill seedlings. Corn uses lots of water, but it doesn’t like wet feet. It thrives with small, frequent water applications.

Farming Smarter 2015 corn plots
Farming Smarter corn plots 2015

Corn roots develop in three stages: the first, seed roots, provide the energy to push the shoot through the soil. About four weeks after seeding, the nodal roots or main roots develop. The brace roots form later.

When it comes to weed control do not trust the Blue Book. Do not use any phenoxy herbicide on corn and check ingredients for MCPA and 2,4-D. They are registered for corn but cause brittle snap– plants bend and fall and a wind is devastating. Surviving plants have ineffective brace roots. Group 27 products like Impact can be tank-mixed with glyphosate to control volunteer canola.