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Row planters versus air drills

There are some benefits to gain from row planters, but your decision to buy one will depend on row spacing and seeding rates

Row planters offer some benefits over air drills when seeding soybeans, according to research done in Ontario and Manitoba. But those advantages won’t add up to a new equipment purchase for every farmer.

Horst Bohner is a soybean specialist with Ontario’s Ministry of Agriculture, Food and Rural Affairs. From 2008 through 2010, Bohner and his colleagues compared soybeans seeded with a 1560 John Deere no-till drill to soybeans seeded with a Kearney 15-inch vacuum planter. Row spacing was set at 7.5 inches and 15 inches for the drill, and 15 inches for the planter. Seeding rates ranged from 100,000 seeds per acre to 300,000 seeds per acre.

“The long and the short of it, there was a small but real benefit in terms of yield. And I think where that comes from is a little bit of a better plant stand, partially. And we think that the reason we’re getting a larger percentage of plants compared to what we’re seeding with the planter is because of depth control,” says Bohner.

Soybeans seeded with the planter in 15-inch rows yielded about 1.8 bushels per acre more than soybeans seeded with the drill in 15-inch rows. The planter also yielded a 5.2 per cent plant stand advantage. When compare to the 7.5-inch drill, the planter yielded 0.8 more bushels per acre, and had a 7.3 per cent bump in plant establishment 30 days after seeding. There was no difference between plants seeded with a 15-inch drill and a 7.5-inch drill.

Higher seeding rates increased yields significantly. Researchers found the most economical seeding rate at 7.5-inch spacing was about 186,000 seeds per acre.

Bohner says the planters and the drills seemed to work best when seeding at a depth of 1.5 inches to 2.5 inches. The drill doesn’t seed as well at an inch to 1.5 inches.

“The planter is not really quite there either, but at least it’s a little bit better when you’re seeding more shallow,” says Bohner.

Manitoba trials

Brent VanKoughnet, owner of Agri Skills Inc., ran seeding trials for the Manitoba Pulse Growers Association from 2010 through 2012. The trials, located near Carman, Man., looked at using planters and air drills at different seeding rates and row spacings.

“Under the broadest range of conditions, the planter seems to be a reasonable hedge. You’re more likely to get a better plant stand with a planter across the broadest range of growing conditions,” says VanKoughnet.

Seed placement is more important in wider rows, VanKoughnet says. Large gaps in seven or eight-inch rows likely neighbour areas with higher seed concentrations.

“If you had gaps like that in a 30-inch row, then you’d have seeds right on top of each other because it’s so concentrated. And then you’d have spaces that would be kind of a waste.”

In 2010, soybeans were seeded in eight-inch spacings by a Bourgault single-manifold air drill, and 10-inch spacing by a John Deere multi-manifold air drill. A John Deere max-emerge vacuum planter, set on 15-inch spacing, was also used. High, medium, and low seeding rates were set for each implement.

Too much rain after seeding stressed all the treatments, particularly the John Deere air drill with on-row packing. Though there was a yield penalty due to poor emergence, it was less severe than expected.

“By looking at the fields, they looked like they were going to be 50 per cent of the yield, and you ended up with 80 per cent of the yield, or something like that,” says VanKoughnet.

Hail robbed yield from all the treatments, but as the treatments were replicated four times, each treatment was likely affected equally by the hail, VanKoughnet says.

The planter set at 15-inch spacing yielded better than the other treatments, no matter the seeding rate. At the lowest seeding rate of just over 140,000 seeds per acre, the 15-inch spacing yielded 31.5 bushels per acre. The 15-inch spacing seeded at the higher seeding rate also had the highest yields, of nearly 34 bushels per acre. The 10-inch spacing yielded around 29 bushels per acre at each seeding rate, while the eight-inch spacing yielded about 30 bushels at the lowest rate, to 32.4 bushels at the highest rate.

In 2011, VanKoughnet looked at eight-inch row spacing with an air drill, and 15- and 30-inch spacing with a vacuum planter. All the plants got off to a great start, but then the taps shut off. Lack of moisture became a key factor.

“It didn’t matter how many seeds you planted, and it didn’t matter what row spacing there was. It all came to that maximum yield of about 41.5 bushels or somewhere around there.”

Dry weather in 2012 punished some soybeans in 30-inch spacings. VanKoughnet says the upright, early-maturing variety in the 30-inch spacing was too mature to benefit from a crucial early August rain. The crop canopy filled in later and barely covered the rows, allowing sun and wind to dry the exposed soil.

The upright, early-maturing variety in eight-inch spacing was about a week behind, and fared better. The later-maturing, bushy variety didn’t suffer a yield penalty in the 30-inch spacing.

Manage trash during seeding

The right equipment can help farmers manage residue during seeding.

Bohner says lots of residue can be difficult for the equipment to punch through, and may cause emergence problems.

“If there’s a lot of residue from the previous crop in no till, then sometimes by going with a little bit of a wider row like a 15-inch over 7.5, you can put some more coulters on there and try and push some of the trash out of the way,” says Bohner.

Managing the trash could prevent frost damage, too. VanKoughnet had coulters in front of the planter row for some strips, which moved the trash about one inch from the soybeans.

“And there was no frost on those beans. And where the strip of trash had not lifted, and was right over top of the beans, they were frozen back to the cotyledons.”

VanKoughnet says this was replicated seven times across the field. His experience has implications for farmers seeding early into no till.

“I would wait and make sure I got good, warm soil and then pop them into the ground, particularly if there’s a bunch of straw.”

New equipment?

Does the potential for better seed placement warrant the purchase of new equipment?

Boehner says there is no question the planter is superior for seeding in 15-inch rows because it does a better job with depth control and seed distribution.

“The confounding factor here is that if you don’t have a planter unit, and you can only go in 7.5-inch rows, then that’s okay too. The way to get around any problems with that distribution issue is just to keep the seeding rate on the high side, and then it all washes out anyway and it doesn’t really matter,” says Boehner.

But farmers who want to cut seeding rates will want to consider a planter.

“So far (in) the comparisons we’ve done, we’re adding close to 20,000 more plants in an air drill than we would with a planter. And at the price of seed right now, that bumps around $11 an acre,” says VanKoughnet.

Farmers looking at a 30-inch planter should keep in mind 30-inch rows will likely require an extra pass with the sprayer to control weeds, partially offsetting savings from lower seeding rates.

Though cheap 30-inch planters are readily available in the United States, finding an affordable 15 or 20-inch planter is more difficult. Farmers who plan to grow corn as well, or who have many acres to seed to soybeans, may be able to justify the purchase.

VanKoughnet says farmers should also consider how new their air drill is. He says researchers need to compare the vacuum planter’s performance to that of new air drills with single disc offsets, individual depth control, and individual packing.

Ultimately, an air drill gets the job done.

“You can’t wreck a soybean crop from the piece of equipment you use, if it’s doing its job right. You can get a good soybean yield with the planter or with an air drill, if the conditions are right,” says VanKoughnet. †

About the author

Field Editor

Lisa Guenther

Lisa Guenther is field editor for Grainews based at Livelong, Sask. You can follow her on Twitter @LtoG.

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