Crop Stalker targets weeds between rows

While Canadian farmers can seed between stubble rows with equipment such as the Seed Hawk SBR, Australian farmers spray between rows of growing crops with the Crop Stalker.

The principle behind the two machines is the same: keep the working tool precisely in the middle between two rows.

But what they do and how they do it is different.

The Crop Stalker in-crop spray system uses a rigid shield with a nozzle mounted inside pointing down toward the weeds.

The front end of the nine-inch wide shield is pointed like a canoe so it smoothly glides in the gap between growing rows seeded on 12 inch spacings, without causing excessive air movement. The system uses 12 inch wide shields for rows on 15 inch centers.

Nozzles in the shield hit the weeds between the rows and no herbicide escapes to affect the crop, says Grant Yates of Southern Precision in Naracoorte, South Australia, which builds the Crop Stalker.

“The bottom of the shield runs on the soil surface. You can walk behind while it’s spraying and there’s no chemical smell at all,” Yates said.

“The shield seals everything inside. We have yet to hear of any crop damage or off target application.”

Yates said there is minimal air movement at ground level, which is what they want to achieve good coverage on weed surfaces. Vertical slots at the front and back of the shield prevent it from creating a vortex while spraying at speeds up to 15 km/h.

“When we get a wet summer, there’s always a lot of in-crop spraying. But guys really want to use something other than Roundup in the paddock,” Yates said.

“When they have Roundup resistant weeds, guys use their Crop Stalker to take them out. They use a precision application of Paraquat sprayed between the rows, or they use a good mix of Paraquat with Diaquat.”

He said lentils have become a significant crop in Australia, partly because the Crop Stalker has allowed farmers to grow lentils on ground previously unsuited for the crop because of weed pressure.

“Now they get a clean crop with very little weed competition for moisture and nutrients,” he said.

“And after harvest, there’s virtually no cleaning required before going to market.”

Yates said some farmers use the Crop Stalker to make a double application in a single pass. While the Crop Stalker is spraying weeds between the rows, another set of nozzles mounted over the crop rows can apply fungicides, insecticides or liquid fertilizer.

“You know for sure none of that product will be wasted on your weeds because they’re covered by the shield as the nozzles pass by,” he said. “It’s extremely precise spraying. Guys put the nozzles within one foot of the crop. There’s no waste.”

While high-value lentil fields are the main justification for investing in the Crop Stalker, the device is also used in wheat and barley on a 12 inch spacing.

“We’re looking at doing some R & D now on crops with 10-inch row spacing. That’s a pretty tight fit, but I’m sure we can make it work.”

Controlling a 40-foot boom so the shields stay exactly in the middle between rows is the obvious challenge in making the system work.

“We use the Robocrop2 XHD Side Shifter made by Garford in the U.K.,” Yates said, adding that it has a full 50centimetre lateral steering movement to keep the shields centered between the rows.

“That’s absolutely essential to making this whole system work. It was originally designed for precise inter-row cultivation in a growing crop, but it’s perfect for what we’re doing. It’s something like your Canadian Seed Hawk’s Seed Between the Row device, but it doesn’t use mechanical paddles or feelers.”

Yates said instead of GPS or special electronic devices to keep the shields centered Crop Stalker uses an off-the-shelf AgCam video camera mounted on the toolbar near the centre of the boom.

The Ag Cam looks at a panorama of four rows. When the operator gets into a new field, he programs it for exact row spacing and crop development stage of small, medium or large. Operators can also adjust for different crops by putting different filters on the camera.

Southern Precision has not yet found a filter that detects standing cereal stubble.

“We would like to use the Crop Stalker to seed between the rows like your Seed Hawk Seed Between the Row option,” Yates said.

“We have absolutely everything to make it work perfectly, except the right filter for the camera. We haven’t found a filter yet that clearly identifies the colour of standing stubble.”

He said the camera feeds video into a computer, which then instructs the Side Shifter to make minute adjustments left or right, which keeps the sprayer travelling between the rows.

The videos posted on the Southern Precision website show the sprayer running at eight to 10 km/h.

“But we’ve sprayed at 15 km/h without losing our precise accuracy.”

Not everything about the Crop Stalker is foreign to Canadian farmers. In addition to the AgCam, it also uses a Teejet 430 flowback spray control manifold and Wilger nozzle blockage monitors.

A 40-foot Crop Stalker carries a price tag of $100,000, which includes the AgCam and the Side Shifter, normally valued at about $33,000.

For more information, contact Yates at or visit

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