Tractor based remote sensing for variable nitrogen fertilizer application

Precision farming requires accurate and efficient tools to determine the N fertilizer requirement not only as an average for the field, but also to enable variable application of N within a field. A tractor based remote sensing tool has been developed to determine the N status of the crop and deduce its future N fertiliser demand. Connected to a variable rate spreader, this technique enables an on-line variable N application according to the actual N demand of the crop. In 1999 the performance of the sensor system was tested on cereals (winter wheat, winter barley) in 96 field trials. Variable nitrogen application increased yield (on average by 1.6 dt ha−1) and protein content, compared to the uniform application of the same total N amount.