Field-scale validation of a tractor based multispectral crop scanner to determine biomass and nitrogen uptake of winter wheat

In spatially variable fields, nitrogen fertilisation should be site-specifically applied in the growing season. This can be achieved through on-the-go sensors detecting the nitrogen status of the plants combined with a fertilising algorithm to control the amount of nitrogen fertilizer being applied. The potential to detect the spatial variation of biomass, nitrogen content and nitrogen uptake in winter wheat was investigated in 2001 and 2002 with a tractor based multi-spectral scanner measuring crop reflectance. The results indicated that biomass and nitrogen uptake can be reliably detected with a tractor-based non-contacting sensor. Further, the spatial yield variation can be predicted based on spectral measurements at milk ripeness.