Lacer-induced Chlorophyll Fluorescence - a Tool for Online Detecting Nitrogen Status in Crop Stands

Abstract

The on-line monitoring of crop stands is essential in a system of site specific N application. The chlorophyll fluorescence ratio F685/F730 is correlated with chlorophyll content and nitrogen content. Therefore monitoring the laser-induced chlorophyll fluorescence might be used to assess the N status of plants. During the 2000 growing period field campaigns were done with a hand held device to measure the fluorescence ratio F685/F730. Fluorescence ratio was negative correlated with N content and in late growth stages with N uptake as well. The coefficient of correlation was between r=0.976 (N content in dry matter in EC 30 against fluorescence ratio) and r=0.737 (N uptake in EC 37 against fluorescence ratio). The experiences of the 2000 measuring campaign will be applied for the further improvement of the technical design.