Pre Emerge Spraying with a Custom Applicator: Drive-Along Diaries #3

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About Jason Deveau (Spray Guy)

Dr. Jason Deveau has been the OMAFRA Application Technology Specialist since '08. He researches and teaches methods to improve the safe, effective and efficient application of agricultural sprays in specialty crops, field crops and controlled environments. He is the co-administrator of Sprayers101, co-author of the Airblast101 Textbook, a slow cyclist and an even slower runner.

See all posts by Jason Deveau (Spray Guy).

Clean Field Services

It was May 16th, and I was standing at the front counter of Clean Field Services (CFS) in Drayton, Ontario, looking forward to an interesting day in the buddy seat. While I was waiting on the sprayer operator to check and fill the sprayer, I asked Todd Frey, Customer Service Rep, to give me some background into the company.

Todd’s father, Dennis, started spraying for a neighbour in the 1990s using a truck-mounted skid sprayer. In 2003 he began offering custom application services from their Drayton location, and in 2009 incorporated as CFS. Primarily offering contract application services to small fields (<20 acres), they also offered scouting and agronomy services, sold seed, and created nutrient management plans.

A big part of the business is liquid fertilizer. Many local retailers are set up to apply dry fertilizers, but here they pre-blend liquid fertilizer and can fill a sprayer in three minutes thanks to their new John Blue, 20 hp pump with it’s 4” inlet. More on tendering, later.


Todd explained that today would be all about pre-plant herbicides in soybean and corn. The farmer tills, then CFS sprays, then the farmer tills again to incorporate the herbicide before planting.

Much of the scheduling is arranged over the previous winter, but plans had to be flexible to accommodate changeable weather. Case in point, there were originally six jobs scheduled for today, but two were added at 6 am when clients called to ask for last-minute service. The wet spring was keeping farmers off their fields, so planting pressure was mounting, and sprayer scheduling had been particularly tough. Todd tells people “We’re not 911 dispatch!”, but ultimately does his best to accommodate the short notice.

That’s when Brendan Bishop came in to collect me. This was Brendan’s second year as an operator having started in 2023 as a tender truck driver and “graduating” mid-season to spraying. As I followed him out, I wondered how he’d stack up compared to the older, more experienced operators I’d worked with. Spoiler: Brendan had skills.

The Sprayers

CFS owns a John Deere 410R and a 4038. They also have an operator on retainer who owns his own 4030. CFS used Rogator in the past and Apache before that. The Rogators featured a lot of flow capacity, making them great for spraying 28%. CFS switched to Deere for the service and to take advantage of a few technologies I’ll describe shortly, and now they can stream liquid fertilizer at rates as high as 46 gpa at 14 mph.

Today, we’d be in the 410R, which featured pulse width modulation (PWM) and boom recirculation. I was told that customers appreciated the optics of not wasting up to 40 gallons on priming. But the sprayer also featured direct injection from four, 50 gallon tanks, and that puzzled me. Why would a sprayer have two seemingly incompatible features? No one would inject product just prior to the manifold and then circulate it right back to contaminate the tank.

Brendan agreed that they were mutually exclusive, but both had roles in minimizing waste and downtime from priming, rinsing, and custom spray mixes. For example, an early pass over corn might have Marksman and Armezon PRO in the tank, and then Roundup could be direct injected at rates specific to the weed pressure. On the other hand, if he didn’t need direct inject for custom mixes, he could utilize recirculation to avoid priming.

The sprayer automatically disengaged recirculation when direct injection was operating. That restriction could be over-ridden, but you couldn’t run them both by accident. Nevertheless, his policy was to always take a breath before engaging either system because a mistake might be irreversible and require a purge and refill.


We left the yard and cruised down country roads at 40 mph until we hit the more populated regions. This part of Ontario had a lot of Mennonite residents, and their horse-drawn carriages required a wide berth. That got particularly tricky on narrow roads and single-lane bridges, but Brendan was patient and obviously practiced.

We arrived at our first field at 8:50. We parked at the edge and started unfolding the boom as Brendan called dispatch on the cab radio. The field was 15 acres of Roundup ready corn, and we’d be spraying a pre emerge herbicide in 28% UAN at a rate of 20 gpa. We knew all this before we ever left the yard thanks to CFS’s operations management system.

The AgLogic Operations Management System electronically assigns work orders (e.g. chemistry, field location, field boundaries) to the equipment, allowing dispatch to track, schedule and route their assets. It also pushes weather information and any special notes to the operator. The AgLogic tablet and the John Deere monitor are supposed to be compatible with one another, and it was generally slick, but there were a few glitches.

AgLogic and the Job Centre monitors showing how the boundaries were different for the same field. The operator has to make a commonsense call.

Dennis was on dispatch, and Brendan asked if he should send for Simon, their tender truck operator. He was going to need water for the next job and had planned this job to end as empty as possible. Dennis agreed to send him as Brendan noticed aloud how rough the ground was – this field had only just been plowed. Dennis said they’d had to wait for the farmer to plow and warned Brendan of a particularly bad patch that he was familiar with. Brendan signed off and smiled as he warned me to hold on tight. Then he hit start on the AgLogic work order, and we were off.

He wasn’t joking – this ride would have qualified as a theme park roller coaster. I’m sure I left hand and face prints all over his windshield. He had to turn off boom track and go manual and had to cut a second headland. It was hard to hold the rate steady because our 4 mph speed dropped the PWM to the minimum 25 PSI and the duty cycle was maxed out.

Eventually we got up to a roaring 7.7 mph and by 9:25 we were done with less than two gallons left in the tank. While I searched for my kidneys, Brendan entered the summary into AgLogic: 19.65 gpa. He added a few choice comments to the file and in less than a minute he was done. CFS now had the information for billing with no hardcover book for the operator to mess up and no bad penmanship to decipher. As I said, slick. Have a look at a field ticket, here.


We waited in the client’s yards for Simon. Brendan said he’d fill wherever he needed to; on the shoulder of the road or slinging the hose across a ditch into the field. But a client’s yard was always safer and therefore preferred. It was worth waiting.

According to the work order, the next job was 15 acres of Roundup burndown at 12.5 gpa, so Brendan was doing the math on how much water he’d need (plus one acre’s worth for buffer). Simon showed up at 9:42 and we were loaded by 9:45. Just before we hit the road Brendan called dispatch to ask where to send Simon next. Efficiency takes planning.


We parked at the field entry and Brendan engaged the recirculation to push the remaining UAN and pre-emerge in the lines back to the tank to dilute them. Then he turned it off, engaged the direct injection of Roundup, and started priming the boom. This sprayer featured Auto Boom Prime: The operator set a target displacement volume (in this case, 40 gallons) and when the flow meter reached that value, you were primed.

As we waited Brendan explained that we weren’t doing anything today that couldn’t handle a little Roundup, so even if it somehow did circulate back to the tank, it was no big deal. He started the work order log at 10:02 checked for any warnings associated with the field before we were off again.

This was a narrow field. So narrow that we would likely overlap in the middle just from spraying the boundary. Brendan drove that first side manually, cleaning up the corners and margins while skillfully dodging fenceposts as best he could. Nevertheless, we tested the breakaway section a few times. He was nonplussed and said that any operator claiming they’ve never nicked a tree or a fencepost is either too far away or lying.

I asked why he didn’t use fencerow nozzles with Roundup and he gave two good reasons: 1. If you succeed in burning out all the grasses, broadleaf weeds like burdock move in and cause new problems. 2. Overspray was too risky when the target field abuts another crop.

Regarding his second point, I saw what he meant as we turned to spray the rest of the boundary, right next to winter wheat. On the back of the joystick are the secondary controls, which Brendan used to nudge the boom a few inches left or right along A-B line, constantly adjusting for the wheat.

At 10:17 he closed the work order, which digitally winged its way back to CFS for accounting. We folded up and followed behind as we headed back to the yard for a refill. Going back made more sense than tendering since the yard was en route to the next job.


CFS fills their 20,000 gallon holding tanks from their own well, which is 300 feet deep and rated at 4,000 gallons per hour. Instead of installing more holding tanks, they doubled the floats to half the refill time. In addition, they have a tractor-with-wagon tender system with a 4,000 gallon capacity (and four serial induction bowls). Their transport truck is strictly for carrier and has two, 4,000 gallon tanks. In total, they can have 32,000 gallons of water on hand.

They recently improved their transfer pumps to keep up with so many small acreage jobs. It used to take up to 25 minutes to fill a 4,000 gallon trailer. Now they can pump up to 480 gpm through 4” lines and fill that same trailer in less than 10 minutes. And they have two such fill systems so no one has to wait their turn.

Their efficiencies are now found in the logistics of planning jobs that avoid rinses and minimize sprayer travel time where possible. The company isn’t afraid of road miles, preferring to drive further between jobs to avoid having to clean out the sprayer. Floating the sprayer to save engine hours didn’t made economic sense for them since you needed a wide-load permit, time to un/load the sprayer and you couldn’t transport at night.

It wasn’t “Gone in 60 Seconds” but we weren’t there much longer than that.


The next job was an L-shaped field. Brendan noted that weird field shapes were par for the course. As we drove, he said that some fields were so tight that he had to fold the booms almost completely to fit while spraying. He said he’d sprayed fields that no 120’ boom had any business being in. He’d had sideview mirrors pushed against the cab and was happy the Deere plumbing wasn’t on the outside of the folded booms, because he’d been snagged by branches in other sprayers.

Speaking of the boom, he was using LDM 08 nozzles, and the height was set to 30”. He would have liked a lower boom, but it wasn’t realistic on these rough and rolling fields. This field was short and sweet, and we were soon headed out.


This field was 19 acres and once again I saw it was narrow, meaning a lot of manual spraying on the boundary and very little autosteer in the middle. Brendan scanned back and forth between the boom end, the monitor, and ahead of the sprayer as we drove along at 7.5 mph.

When I mentioned the lack of autosteer he said he didn’t get to use it as often as I might think. Many of the corn fields he sprayed were planted by farmers with no GPS, so while he did use the A-B lines, they were mainly to alert him to turns. The actual steering was manual as he followed the planting lines.

I should mention that Brendan established a new boundary for every field, even through AgLogic provided one. He elected to establish this new boundary because once he sprayed the perimeter the monitor could tell him exactly how much area was left to spray. So, he would spray the boundary, check the area remining, and use his cell phone to calculate the differential between the volume in the sprayer and the target rate. He did this now to ensure he had enough water for the last four acres. He wanted to end empty because he would be switching back to 28% UAN next. Based on his math, he pushed the rate to 20.5 gpa to use up the water.

These rate changes would be difficult (perhaps impossible) to achieve without PWM because it would be based on pressure changes, and not duty cycle. It might even require switching nozzles. This is also when direct inject shines as it could maintain the Roundup rate independent of the carrier rate. Brendan said that fields were somehow always bigger than expected, so he was a big fan of the flexibility these features afforded him.


Now we’re back in the yard to fill with 28% UAN. Brendan was planning on a six acre corn field in the Township of Southgate, which was about a 45 minute drive, so we had to fill precisely.

We arrived at 12:27 and had to ask the client where the field was on the property. Surprise! The client wanted us to do eight acres, or 25% more than we’d anticipated. There was no way we could stretch the load that far, so Brendan told him we’d drive all eight at a reduced rate and make up the remaining nitrogen later when he came back with drops. We adjusted the rate from 28.75 gpa UAN to 22.6 gpa and at 12:46 we were done spraying, and the job submitted.


Simon is back with water and Integrity for our next job in pre-emerge corn, which is why Brendan wanted to be empty of 28% UAN. By 1:02 we were full and headed to a 32 acre job spread over two fields. Brendan chose to do the smaller, four acre field first so if he had to make any rate changes in the second field, he could spread a smaller difference over more area. Clever.

But where was this little field? Turned out, it required us to drive through a swamp, flushing two ducks and a deer in the process. As if that wasn’t bad enough, we both started to laugh when we saw the field. The ground must have been plowed 10 minutes before we arrived because it looked like an earthquake had hit it.

There’s a good reason you don’t spray freshly plowed fields. Once again, I did my pinball impression and idly wondered if Deere didn’t install seat belts in the buddy seat because they were trying to dissuade people from using it. Even Brendan bounced around despite the air ride driver’s seat.

We were relieved that the larger of the two fields was a breeze. Brendan did his math trick and elected to nudge the 16.1 gpa up to 16.7 in order to end empty. By 1:45 we were off for our last tender of the day.


The last three jobs totaled 70 acres and required a single fill. We were moving into Roundup-ready soybean, so we’d be spraying Roundup Transorb HC (glyphosate) + Tavium (S-metolachlor and dicamba). Brendan said they’d clean the sprayer thoroughly afterwards if they had to, but it was preferable to schedule a series of corn fields for tomorrow because they wouldn’t be bothered by dicamba residue.

We met the tender wagon and Brendan and Simon started loading Tavium into the inductor bowls for transfer to the sprayer. Then Brendan hosed down each bowl to rinse them and transfer that rinsate into the sprayer as well. Afterwards Brendan used the inductor bowl on the side of the sprayer to rinse the jugs because he felt the water pressure was higher on the sprayer and did a better job of cleaning them out.


This was a 11.75 acre field, and it should have been simple… but it seemed nothing was. The work order map showed the digital boundary, but the actual plowed field was much larger. So, it was one continuous field and we were supposed to spray only part of it. Where exactly was the boundary?

Eventually Brendan spotted some unsprayed grass that hinted at where other equipment had driven in the past. That subtle visual cue would have been impossible for an operator to see in the dark.

As we positioned ourselves to start spraying we saw the note on the work order to “mind the garden”. Garden? What garden!?

Eventually “Eagle-eye” Brendan spotted a couple rusty, foot-long lengths of rebar hammered into the soil along the edge of the field. They were perfectly camouflaged to match the colour of the tilled earth, hungry to puncture the tires of the unsuspecting, and doing a very poor job of indicating a “garden”. Once finished, we primed the boom (40 gallons) on the field margin to have it ready for the next job.


According to the work order, this 37 acre job warned us of yet another small garden. This garden was emerged, making it easier to find, but also making it a nerve-wracking off-target risk. So, we literally steered clear of it, leaving a wide berth.

That didn’t stop the woman who was tending the garden from marching purposely out to sprayer to get Brendan’s attention. He stopped and braced himself as he climbed down to speak to her. We both expected he’d get an earful for spraying around those vegetables. After a brief exchange he climbed back into the cab and smiled. She didn’t chew him out – she chastised him for not getting close enough! You can’t win.


The last field was 20.5 acres. It was flat, square and promised to be a straight-forward end to a complicated day. We drove 9.6 mph on the headland and just as we were finishing the circuit, we saw tilled earth outside the boundary indicated on the monitor. Wait – is that bit planted, too? Are we supposed to spray that as well?

Brendan guessed it was an additional three acres. He’d asked Simon to load an extra acre’s worth of spray mix when we loaded, and I now understood why. He did some quick math and said we’d have enough if we dropped the rate a bit.

We coasted back and forth over the field, watching the remaining volume drop on the monitor, hoping we’d make it. We considered adding rinse water to the tank to thin the concentration. That would give us enough volume, but we’d be diluting the chemistry too much. Then we figured if we had to we could empty the tank just to the point of starving the pump, add water from the rinse tank and push the ~40 gallons left in the lines from behind.

The tiny, unsprayed strip caused the PWM to flutter between one and three nozzles on that last pass. Neither of us realized we were holding our breath as we watched the spray volume drain away on the monitor.

And then we were done! It was a photo finish and we both let out an explosive gasp as we started breathing again. It was such a narrow victory that we climbed out to look in the tank, and I’m here to tell you, it simply does not get any closer than this. We bragged like successful hunters all the way back to the yard and told anyone that would listen when we arrived at 5:00.

As I packed to leave, Brendan asked Dennis if he had to go clean out the sprayer. Dennis said a little dicamba would help tomorrow morning’s pre-emerge applications, so no. But he smiled as he warned “Although, betcha someone will call in at 6 am to ask for IP beans first.” Driving home, thankful for my comfortable car seat, I wondered if they would.

Take Homes

  • Planning ahead is always good advice. However for a custom applicator, it’s absolutely critical. The goal is to be efficient and effective with as little risk as possible, and you can’t accomplish that unless you know where you’re going, when you’re going there and what to expect when you arrive; and not just the immediate job but minimum three jobs ahead. When time, manpower and consumables equal money lost, the stakes are high to have a solid strategy before you leave the yard.
  • Then again, rigid planning can be A BIG MISTAKE… unless it includes planning for the unexpected. Almost without exception, these fields were not as advertised. Most were larger than anticipated, so knowing how to stretch a load (e.g. dilution, changing rates, carrying a little extra, using clean water to push spray mix from behind) meant we could roll with the punches without leftovers or deficits. One strategy was to spray smaller fields first, so larger remaining fields could absorb a smaller, distributed differential. Another was to spray the headlands, calculate the remaining area, then determine a rate that fits the remaining volume in the sprayer. This all assumes you performed some solid sprayer math when you loaded, of course.
  • Autosteer, while awesome, was not used near as much as I expected. Small, irregularly-shaped fields that were recently ploughed, abutting sensitive crops and land-mined with “no spray” gardens meant manual headlands (maybe two) and slow speeds. And when the client doesn’t use GPS to plant, you don’t use it to spray except to alert you to turns. Anyone that thinks the operator can be replaced by automation should ride along in these conditions. There are lots of situations where we still need grey-matter and experience behind the wheel.