Mr. John Dolan:

The mapping of the fields would be done once. When the spreader comes to an angle in the field or a sensitive area for conservation, the discs of the machine will slow; if it keeps driving into that area, they will eventually stop and shut off the machine. It is impossible to spread in it.

On the question about saving, all these modern variable rate fertiliser spreaders have an accuracy level of +1% to -1% over a huge area. The accuracy level is 10% above standard GPS-guided application with a blanket spreader.