Uniform plant stands boost seed yield

Researchers increased canola seed yield up to 32 percent at low-yielding sites and by 20 percent at higher yielding sites

Using her index finger, Justine Cornelsen pointed toward five small plants, clumped together in the corner of a plastic tray filled with soil.

The canola plants were less than seven centimetres high because they had just emerged from the soil. Cornelsen, a Canola Council of Canada agronomist in Manitoba, took a quick look and then predicted the fate of the cluster of plants.

“When you see this clumping here, these other … plants are going to die off. The two bottom ones aren’t going to make it,” she said at CanoLab and SoyLab, an agronomy workshop for canola and soybean growers held last month in Brandon.

The soil trays and cluster of canola plants were used to illustrate what happens when a plant stand is not uniform.

Agriculture Canada research on canola, conducted at Swift Current, Sask., and other sites in Western Canada, determined that uniform plant stands increased seed yield up to 32 percent at low-yielding sites and by 20 percent at higher yielding sites.

“The yield increase was more pronounced with plant densities lower than 60 plants per sq. metre (5.6 plants per sq. foot),” said Yantai Gan, Ag Canada scientist in Swift Current, in a paper published in 2014.

“We conclude that canola yield can be increased by improving the uniformity of plant spatial distribution patterns in the field regardless of environmental conditions.”

Non-uniform plant stands, where canola plants emerge in an arbitrary fashion rather than a tidy pattern, can increase the number of seeds that fail to germinate and the number of plants that die early in the season.

“When we see seed clumped together … into groups of three or four, all of a sudden our emergence goes down to one or two (plants) that will grow,” said Greg Sekulic, Canola Council agronomist in Alberta.

“Something in the chemical signals from those seeds, that are placed too close together, will actually inhibit the germination of the ones around it. So, our germinations go way down…. So 50 to 75 percent mortality, pretty much right off the bat.”

As a rule, canola council agronomists assume that 60 percent of canola seed survives and becomes a full-fledged canola plant when seed is planted with an air drill.

But that number could be pushed higher if the seed is planted in a uniform manner. That’s why the survival rate is much higher when canola is seeded with a planter.

“We do see seed survivability well into 80s and 90s percent coming out of planters,” Sekulic said. “The uniformity is a huge part of it.”

Corn planters, though, are expensive and are only common in Manitoba’s Red River Valley, where crops like corn and soybeans are prevalent.

Western Manitoba growers that do minimal tillage haven’t had as much success with planters, Cornelsen said.

“(They) aren’t overly happy with the results, yet, because they can’t manage residue,” she said.

“In the Red River Valley, they till everything black, where the planter can go in and do a really good job.”

In lieu of a planter, there are other ways to increase the uniformity of seeding and plant establishment. One way is checking the drill more frequently at seeding time to ensure there isn’t a blocked run, Cornelsen said.

As well, with wide drills and rolling terrain it can be challenging to control seeding depth across the entire width of the drill. Seed may end up too shallow or too deep, thus reducing seed survivability and plant stand uniformity.

One possible solution is buying a drill with independent terrain-following openers, which increases control of seed depth and also increases the percentage of seed that survives.

Another factor that influences the uniformity of the plant stand is fertilizer placement with the canola seed. Too close can be toxic.

A good resource for more information is at bit.ly/2IHOFj4.

Getting it right, so there is a uniform plant stand, can increase yield and also reduce cost. If a grower can achieve a uniform stand it’s possible to cut back on seed and still maximize yield.

“With seed at $10 to 15 a pound now, if you can reduce your seeding rate … cutting a pound or two becomes a pretty substantial cost savings,” Sekulic said.

“In a non-uniform plant stand, where it’s missing a bunch of plants but it’s averaging eight (per sq. foot), we can still see 100 percent of our yield potential. If we get down to five plants per sq. foot but they’re uniform, we’ll still see 100 percent yield potential.”

Cornelsen said improving plant stands and uniformity begins with scouting fields, following harvest. Growers should be targeting a certain plant stand and then checking to see if they achieved the target.

“That’s the big missing link. If you’re not going back at harvest to see how many plants actually contributed to your yield, you’ve got no record.”

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