Distortion of the SPAD 502 chlorophyll meter readings by changes in irradiance and leaf water status

- The SPAD 502 Chlorophyll Meter can estimate leaf chlorophyll content as a surrogate measure of the nitrogen (N) status of plants, and therefore, it can be used to assess the N requirements of crops. In this work, we show that irradiance, leaf water status and time of measurement (i.e., morning vs. afternoon), may interfere with the SPAD 502 measurements. SPAD values increased by 2-3 units as relative leaf water content decreased from 94 to...