Assessment of Portable Chlorophyll Meters for Measuring Crop Leaf Chlorophyll Concentration

Abstract

Accurate measurement of leaf chlorophyll concentration (LChl) in the field using a portable chlorophyll meter (PCM) is crucial to support methodology development for mapping the spatiotemporal variability of crop nitrogen status using remote sensing. Several PCMs have been developed to measure LChl instantaneously and non-destructively in the field, however, their readings are relative quantities that need to be converted into actual LChl values using conversion functions. The aim of this study was to investigate the relationship between actual LChl and PCM readings obtained by three PCMs: SPAD-502, CCM-200, and Dualex-4. Field experiments were conducted in 2016 on four crops: corn (Zea mays L.), soybean (Glycine max L. Merr.), spring wheat (Triticum aestivum L.), and canola (Brassica napus L.), at the Central Experimental Farm of Agriculture and Agri-Food Canada in Ottawa, Ontario, Canada. To evaluate the impact of other factors (leaf internal structure, leaf pigments other than chlorophyll, and the heterogeneity of LChl distribution) on the conversion function, a global sensitivity analysis was conducted using the PROSPECT-D model to simulate PCM readings under different conditions. Results showed that Dualex-4 had a better performance for actual LChl measurement than SPAD-502 and CCM-200, using a general conversion function for all four crops tested. For SPAD-502 and CCM-200, the error in the readings increases with increasing LChl. The sensitivity analysis reveals that deviations from the calibration functions are more induced by non-uniform LChl distribution than leaf architectures. The readings of Dualex-4 can have a better ability to restrict these influences than those of the other two PCMs.

Plant phenotyping relevance

携帯型クロロフィルメータによる葉クロロフィル濃度測定法を複数機器で比較・検証し、換算関数と感度分析を評価しているため、植物表現型取得法が研究の中心である。

Code and data availability

The article describes field/greenhouse PCM measurements (SPAD-502, CCM-200, Dualex-4) and PROSPECT-D sensitivity analysis, but contains no data availability statement, no public dataset deposit, and no author code release. The only URL mentioned (SIMLAB) is a generic third-party sensitivity analysis software tool, nota

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