Sectional control minimizes, but doesn’t eliminate overlap

The theoretical savings are great but overlap still happens, and size of both seed and sections matters

Although overlap can be greatly reduced with sectional control, it can’t be completely eliminated as was shown in trials conducted last year for Alberta Pulse Growers. The study also found there was less overlap of larger seeds (such as peas on left) versus smaller ones (like canola on right).

Unless you farm some magical piece of land where there are no stone piles, hills, water bodies or other obstacles to get around, you will always have some overlap.

That extra seed or fertilizer can cost you big bucks over time — which is why stories about sectional control technology often focus on the potential savings. But the technology and hardware that allow you to turn off (or pull out of the ground) one or more sections on a seeding rig isn’t cheap.

So that prompted Alberta Pulse Growers to spearhead a multi-part project to take a closer look at the benefits and performance of this technology.

The first phase looked at the environmental benefit.

“We know there are emissions from fertilizer in agriculture, especially when over-applied,” said Nevin Rosaasen, policy and program specialist with Alberta Pulse Growers. “We know there are opportunities for the industry to do better.”

One kilogram of nitrous oxide from fertilizer is equivalent to 298 kilograms of carbon dioxide, he noted.

“(Showing) what (a fertilizer overlap) reduction would entail is imperative to policy-makers understanding that farmers are doing more with less in order to achieve the same yield,” he said.

The second phase of the Pulse Growers’ project (done last year) put sectional control to the test in the field, using three different types of air seeders. The study, conducted by the Prairie Agricultural Machinery Institute, involved measuring actual overlap on headlands and going around a set of obstacles — and then comparing that to what monitors reported. The trials were conducted on two crops (canola and peas) and overlap was measured via crop emergence (when the effect of double seeding would be evident).

Some might wonder why there should be any overlap at all, but real life in the field gets complicated. Problems include the retention of seed in the lines in the time between the command and actual stoppage, the shapes and sizes of obstacles, the angle of travel and the type of seed being planted.

While the results do not offer any marquee-worthy magic numbers of how much farmers can save by using sectional control (which depends on the nature of their land and how much overlap they’re getting with their current equipment), the PAMI study suggests a few best practices for the tech.

Katelyn Gaetz. photo: Supplied

One of the biggest is proper calibration, said Katelyn Gaetz, who led the study, which was conducted on a number of Saskatchewan farms.

“A lot of overlap is due to settings — the look ahead, the look behind,” she said. “There’s always going to be overlap — it comes down to minimizing it.”

Most of these settings are provided by manufacturers and dealerships, she added.

Size matters

That said, two factors that clearly affected overlap were implement size and the number of sections. Based on theoretical calculations in best-case scenarios, smaller implements and a greater number of sections reduced overlap.

“If you have just two sections on 80 feet you will have more overlap,” said Rosaasen. “Each individual opener that lifts or shuts off creates way less overlap.”

In a way, each section of a seeder with sectional control is like a little seeder itself. Consider, for example, approaching a headland at a 45-degree angle with the goal of not having any seeding misses. If you’re pulling an 80-foot-wide rig, then you’d have to wait until the last bit of ground was seeded before shutting off the flow of seed. Dividing that rig into eight 10-foot sections just means you’ll have smaller triangles.

“The leading edge of a section has to continue seeding through the entire triangle until the trailing edge has passed to the exact spot. So smaller triangles and more of them result in less overlap,” said Rosaasen.

“Because the implement lifts in sections, that whole section needs to seed through the area before it gets lifted which results in very little to no overlap on one edge, but a greater amount of overlap on the leading edge,” added Gaetz. “If the section was lifted prior to seeding the whole path, there would be misses in the field.”

Ideally, you want to seed to a 90-degree angle to the headland whenever possible but when it’s not, smaller sections are better.

“If your section is down to five feet, it’s better than the eight-feet or 10-feet sectional control, especially when you’re seeding at an angle to the headlands,” said Rosaasen.

Size also matters when it comes to seed.

“We noticed a notable difference between large-seeded (peas) and small (canola) seeds and overlap, with a larger overlap noticed in the smaller seeds,” said Gaetz.

Seed size doesn’t discount canola as a candidate for sectional control, added Rosaasen, but it may require lower fan speeds and — again — more focus on calibration. This can be quite time consuming when switching between heavy- and light-seed crops during a busy season.

“It’s to do with the fan r.p.m.,” he said. “Pea seeds are quite heavy. Producers usually have their wind speeds turned up for the delivery lines so the product is pushed through. When it comes to canola, fan speeds tend to be lower so they don’t crack the very costly seed and affect emergence.”

On-off timing should also be recalibrated between crops, he said.

“We might be able to advise producers that they should change their shut-off speed for canola to turn it off just a tad earlier.”

Rosaasen said he would have liked to have seen the overlap effects of both seed and fertilizer placement. Tracking fertilizer overlap is much more difficult than seed emergence but the trial offered some valuable information.

“What we learned from the seed sizes can probably be extrapolated for bulk densities in fertilizer,” he said. “The heavier or more dense the fertilizer, the more likely it is to clear the manifolds than a fertilizer that isn’t as dense. We can infer some learning in that regard for their climate savings.”

Finally, the research showed the need to ground proof.

The monitors had a pretty optimistic view of what was happening and farmers should scout their fields to check up on them, said Gaetz.

“In most cases, the overlap on the monitors did under-represent the actual overlap,” she said.

About the author



Stories from our other publications