Dutch sprayer specialist Rau is testing a precision sprayer that reacts automatically to weed images taken by onboard cameras, selects the appropriate herbicide and application rate and then spot sprays while moving steadily across the field.

The prototype camera-controlled sprayer is being tested in Germany.

It has three tanks for different herbicides, each with its own sprayline along a 21m boom.

Each sprayline is divided into seven separately controllable sections so that it is possible to have only a 3m treatment area for a particular weed spot.

Typically, the three tanks might contain a grassweed herbicide, one for broadleaved weeds and a specific weedkiller for, say, cleavers or thistles.

Heart of the GPS-navigated sprayer is a computer for identifying weed density and controlling herbicide application.

Development teams from Rau, the precision farming company AgriCon, and two German agricultural universities have already completed tests on 800ha (1980 acres) of arable crops around Bonn, West Germany.

Trial results last year showed that the three-tank approach to weed control can save the equivalent of 35/ha (14/acre) in winter wheat, 24/ha (9/acre) in malting barley and 17.50/ha (7/acre) in sugar beet through its reduction in herbicide requirement.

“We’ve saved as much as 65% on grass weed treatments in winter wheat and more than 50% on broadleaved weed control,” explains Professor Roland Gerhards, specialist in computerised weed identification and precision farming at the University of Hohenheim near Stuttgart.

“Almost as important is the substantial benefit to the environment and to the crop which would otherwise be unnecessarily sprayed in non-weed areas.”

Gone, too, will be the days of waiting for daylight before safely spraying.

The Rau/AgriCon concept – which aims to fit one digital camera for every three metres of boom – will apply the Active Light System (ALS), already used to allow night time fertiliser spreading with the AgriCon Yara N-sensor.

“We are working towards a system that allows round-the-clock work whenever conditions are best,” says Prof Gerhards.

He adds that being able to spray safely in the dark means the times of greatest windstill – often just before dawn and after sunset – can be taken advantage of to lessen drift.

Software programmes have been prepared for oilseed rape, wheat, barley, maize and sugar beet.

These identify the crop plant and the major weeds as well as calculating the optimum threshold level at which to activate the sprayer.

First costings reveal substantial savings.

Capital and running costs for the system last year worked out at 4.65/ha while manually plotted weed maps and application plans ran to over 40/ha.

Overall costs for a new three-tank sprayer with central computer, GPS and camera system were assessed to be 9.44/ha.

Average savings in herbicide costs through using the precision spraying system over six different crops was 18.83/ha.

Next season the RAU/AgriCon team will look at the application of the system for spot fungicide treatments.

fwmachinery@rbi.co.uk