Non-contacting chlorophyll fluorescence sensing for site-specific nitrogen fertilization in wheat and maize

The relationship between laser-induced chlorophyll fluorescence intensity (690 nm and 730 nm), ratio F690/F730 and nitrogen content in wheat and maize was characterized using two different sensors (growth chamber and field sensor). In the field, laser-induced fluorescence was measured at a distance of approximately 3.3 m from the canopy and the sensed area was approximately 6-7 m². The fluorescence ratio F690/F730 was inversely correlated with N content and uptake, dry biomass and SPAD value. The results indicate that nitrogen uptake and biomass can be reliably detected through chlorophyll fluorescence measurements under field conditions.