Precision farming brings 2cm accuracy in 10,000 trial plots at Teagasc Oak Park

The Teagasc Oak Park centre in Co Carlow.

More than 10,000 plots of ground are planted, monitored, and harvested annually in crop research trials at the Teagasc Oak Park centre in Co Carlow.

These field trials are a labour intensive and time critical part of research work on crops which include cereals, oilseeds, protein crops, bioenergy crops, beet, and potatoes.

However, Teagasc has now put in place a GPS-based positioning solution to make the crop research trials at Oak Park more efficient.

The technology used is identical to that available to farmers, although it is deployed in a different way, and the most precise positioning signal (RTK) is used.

This technology will become commonly used on farms as its price falls, according to Dermot Forristal and Brendan Burke of the Teagasc crops, environment and land use research programme.

They were among the key personnel in completely changing the Oak Park crop research trials to a GPS-based, precision system.

Reporting on the system in the TResearch science publication by Teagasc, Forristal and Burke said it has allowed a complete section of the trialling process to be automated.

A typical trial may have from 40 to 400 plots.

Plot size is determined usually by the plot harvester to be used, varying from 1.5m to 2.75m in width and 6m to 24m in length.

Each plot must be individually established, managed and measured.

While speed and efficiency are important in plot management, accuracy and precision are critical.

Already at Oak Park, one-pass plot cultivation and sowing had improved efficiency, and fully instrumented combines with complex electronic weighing systems and data collection had replaced slower manual-weigh system machines.

This left the next but larger step — to adopt satellite-based positioning technology, which eliminates the need to accurately mark out field trials manually in advance of sowing.

Oak Park has adopted this technology over the last two cropping seasons.

Precision agriculture technology, largely based on satellite positioning such as GPS (global positioning system), has been in existence for more than 20 years.

Position-related machine control developed rapidly, allowing it to be considered for field trial use.

The highest-accuracy agricultural RTK GPS offers a positioning signal that is within 2cm of the real position.

This acccuracy is essential for research trial use.

Lower levels of accuracy (4-8cm and 15-20cm systems) are more commonly used on farms.

At Oak Park, RTK GPS is used to automatically control tractor or machine steering, precisely guiding the tractor and implement, more accurately than a driver can achieve.

This allows perfectly parallel and equidistant plots to be sown, and steering lines at 90º angles to a base line.

Tractor display and controller display units guide the tractor, and can control any attached implements .

Setting out trials the old way required accurate surveying/marking in advance of sowing the individual plots, using two to three people with tapes, measuring wheels and ranging poles.

For many trials, it could take the same length of time to mark it out as to sow it (for example, three hours for each).

With weather restricting sowing opportunities, and limited personnel and equipment resources, the attraction of reducing/eliminating this marking out time was clear.

Now, the display unit in the tractor cab shows the driver where the plot lines are, but steering and seeder control are completely automatic, eliminating the need for time-consuming marking out, and accurate steering.

“As the level of deployment being planned had not been implemented by any other research centre in Europe to our knowledge, the specification was carefully chosen,” according to researchers Dermot Forristal and Brendan Burke.

Teagasc went for full-RTK level GPS, giving 2cm positioning accuracy; virtual positioning correction, allowing instant set-up anywhere in the country without the need to install a local base station; autosteer with direct control of the tractor’s steering valve; and in-cab screen/controller allowing seeder control with an electronic actuator.

Five complete RTK control units were purchased, which can be fitted to any of six tractors with full autosteer control.

These are based on Trimble FMX 1000 display/control units and VRS RTK correction signal.

Using the system is simple, according to the Oak Park team.

When the tractor/seeder is driven into a field, a baseline is chosen simply by driving between two points in the field.

The operator sets the plot width, the plot length, and orientation of the plots to the baseline (normally 90º).

Visible plot lines appear on the screen, and the driver lines up approximately with the first line, selects autosteer, and leaves the steering wheel free.

The GPS-controlled autosteer system then steers precisely along the plot, and trips the seeding mechanism at every plot end.

At the end of a run, the operator turns the tractor around, and then sets the controller to steer again, sowing perfectly parallel at the correct distance from the previous run.

Overall, while the technology is expensive (€20,000 per tractor unit), it has been cost effective, allowing a huge trials programme to be implemented with limited staff and machine resources.

The system has worked effectively, and the key benefits have been:

  • Plot seeding: set-up time has been practically eliminated, frequently resulting in a doubling of daily plot-sowing output with a two-person team.

Good plot layout in the field is easily achieved.

This has been achieved with cereals, oilseeds, beans, potatoes, grass and beet.

  • Tramline placement: the system allows precisely positioned cross-plot tramlines to be placed, accurately setting plot length for harvest.
  • Trials in commercial fields: the equipment allows 24m spreading and spraying equipment to be controlled within a commercial field to create a trial lattice.
  • All trials: permanent field-trial baselines can be created and stored electronically to ensure the exact location of trials is recorded for future use.

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