Development and Validation of SPAD-502-Based Calibration Models for Estimating Chlorophyll Content in Axonopus compressus

Chlorophyll content is an important indicator of turfgrass health, but traditional extraction methods are destructive and time-consuming. This study evaluated the SPAD-502 chlorophyll meter for non-destructive estimation of chlorophyll content in Axonopus compressus. Thirty leaf samples were collected from A-40 and A-46, with 15 samples from each variant across five visible leaf color levels. SPAD values were measured in the field, while chlorophyll a, chlorophyll b, and total chlorophyll were determined using 80% acetone extraction and spectrophotometry. SPAD readings showed significant positive correlations with all chlorophyll components in both variants. Five regression models were tested, with strong relationships observed (R2 = 0.8960–0.9639). Nonlinear models, particularly power and exponential functions, provided better fitting than linear models. A-46 showed slightly stronger relationships than A-40. These results suggest that the SPAD-502 meter can provide a rapid and non-destructive estimate of chlorophyll content in A. compressus under the present sampling conditions, supporting its potential use in turfgrass monitoring.