Non-destructive determination of maize leaf and canopy chlorophyll content

The objective of this study was to develop a rapid non-destructive technique to estimate total chlorophyll (Chl) content in a maize canopy using Chl content in a single leaf. The approach was (1) to calibrate and validate a reflectance-based non-destructive technique to estimate leaf Chl in maize; (2) to quantify the relative contribution of each leaf Chl to the total Chl in the canopy; and (3) to establish a relationship between leaf Chl content and total Chl in a maize canopy. The Red Edge Chlorophyll Index CIred edge=(RNIR/Rred edge)−1 based on reflectances, R, in the red edge (720–730 nm) and near infrared (770–800 nm) was found to be an accurate measure of maize leaf Chl. It was able to predict leaf Chl ranging from 10 to 805 mg Chl m−2 with root mean-square error less than 38 mg Chl m−2. Relationships between Chl content in each maize leaf and total canopy Chl content were established and showed that Chl in the collar leaf before silking or ear leaves explained more than 80% and 87% of the variation in total Chl in a maize canopy, respectively. Thus, non-destructive measurements of both reflectance and area of a single leaf (either collar or ear) can be used to accurately estimate total Chl content in a maize canopy.