Sensors that use infra-red light beams to measure the quantity of foliage and chlorophyll in crop leaves (and hence how much N you should apply) are now being used by hundreds of farmers across Europe, says Soil Essentials.

It was showing off the latest version of the Crop Circle system it sells, which uses two or more sensors to give a more accurate reading than the single unit used up until now.

These can be fitted to a sprayer or spreader, or on two linear actuator-operated, folding 3m (10ft) arms at the front of the tractor, says the firm.

The info can then be used to make on-the-spot changes in application rates as the tractor moves through the crop or stored as a GPS map. Cost of the arm-based system is £6000 to £9500.