Top Crop Manager

Precision Ag
Variable-rate planting

Variable-rate seeding may prove to be advantageous when it comes to yield potential and a profit increase. Photo courtesy of Aaron Breimer.

As corn hybrids are being developed to respond better to higher seed populations, interest is growing in variable-rate seeding as a way to take advantage of the yield potential and boost profits.


Aaron Breimer, sales agronomist with Veritas Farm Management, says variable-rate is no longer limited to the “early adapters” of precision ag technology. “I’ve got growers doing significant acres with the variable-rate,” says Breimer. 

Variable-rate seeding matches the seed population to the various management zones of the field. Soil zones with higher productivity would have a different seeding rate than those with lower productivity.
“It takes a little bit of understanding of what is affecting the management zone to decide on what population you want to work with and you have to take into consideration which varieties you’re working with,” says Breimer.

With the introduction of hydraulic-driven planters, farmers can change the seeding rate from inside the cab, altering the rate or the hybrid from one field to the next if they knew the fields had different levels of productivity. Breimer says variable-rate seeding now allows farmers to manage the variability that exists within a field.

According to Breimer, there’s been a change in mindset about precision agriculture since it first came out 20 years ago. The initial approach was to minimize the variability by changing the fertility to make the field more uniform. “We’ve come to the conclusion that’s impossible,” says Breimer.

Precision ag, including variable-rate seeding, is now about making the most of the variability in the field. “Variable-rate seeding is not an attempt to minimize variability within your field,” he says. “It’s actually the opposite. We are attempting to take maximum advantage of that variability.”

For Breimer, the first key step is to collect good data, whether it’s from satellite imagery or layers of data from previous crop years to establish the zones. He’ll then talk to the farmer because the most important
layer of information is the grower’s knowledge of the farm. “I can utilize all those layers and I can create a zone map.

But, ultimately, the grower can tell me where there is a sandy knoll, where there’s a clay ridge and where there is a low area that has poor drainage,” notes Breimer. “That allows me to move things a little bit further. I don’t believe in letting the computer do all of the work.”

The next step is to help the farmer understand how certain varieties will respond to different populations. In most cases, the growers bought their varieties in October, November and December, and Breimer will write the prescriptions for variable-rate seeding in February, March or April.

“Quite often you’re trying to say, ‘OK, this is the variety that you’ve got, how am I going to get the most out of it on your farm?’”

Once everyone agrees on the zones and the variety information, and the populations have been determined, Breimer assigns the populations to the various zones to create a script file, which is loaded into the planter.

“Once the planting is done, we pull the as-applied maps and see how well the planter pulled what it was supposed to do from the script,” says Breimer. “Then we set up to prepare for harvest to pull in that data and start analyzing to see how things actually responded.”

According to Breimer’s numbers, variable-rate seeding has netted an increase of $35 per acre under relatively good weather conditions. Some of the results were limited because there were a few farmers who were willing to push the envelope too far.

“On their best soil, they want to push populations to between 40,000 and 42,000 [seeds per acre],” says Breimer. “We would have had higher than a $35/acre benefit if I’d been able to convince a few guys not to plant 40,000 in certain areas. They would have been further ahead at 37,000 or 38,000. But they still made money. On their worst ground where they had been historically putting down 30,000 or 35,000, it was down to 28,000.”

Greg Stewart, corn specialist with the Ontario Ministry of Agriculture and Food and Ministry of Rural Affairs, concurs that there is growing interest in variable-rate seeding. Noting that his work is limited on the practice, he can neither dispute nor support its economic potential.

“I haven’t done enough research to try to counter what the general trend has been – that variable-rate seeding makes you money,” he says.

On the future of variable-rate seeding, Stewart raises a key question: How do you know if you’re planting the correct rates in the first place? He suggests an automated system is needed that can test the validity of the prescription maps.  

“You need some ground-checking to see whether or not those rates are the right rates,” says Stewart. “If you have a huge area of the field that you’ve coloured pink, the map tells you to plant 38,000, and that’s about all you do. How do you know if the 38,000 was the right thing to do?”

Breimer says such a system was implemented in the scripts for this year. While he can’t share many details for proprietary reasons, Breimer says a check population is dropped in a zone and the software will show how the test strip is performing in the different zones. The product is designed to allow the user to see if the prescription that was delivered is profitable and to learn from the results.

In addition to varying the rate of populations within the field, there’s keen interest in varying the types of hybrids and planting densities on a zone-by-zone basis.

The idea is to plant the high-performing “racehorse” hybrids in the areas of high productivity while planting the “workhorse” hybrids to stabilize yields in other areas. Stewart sees it as the next level in the discussion about planting higher seed populations. It’s not a question of merely planting more seeds per acre across a field or certain zones, but planting certain hybrids at a higher rate.

How willing farmers are to adopt such a specific approach remains to be seen, but Breimer says farm machinery companies are building equipment to adapt.
“With the multi-hybrid planters coming in the near future, we also will be looking at changing not only population, but also varieties, probably in the next three to five years,” he says.

Besides corn, Breimer also expects to see more interest in variable-rate seeding for other crops. “We’re heavily involved in variable-rate soybeans and variable-rate edible beans, and then tying in variable-rate fertility to match what you’re planning on putting down for populations,” he says.


September 22, 2014
By Blair Andrews