Assessing Seasonal Effects on Identification of Cultivation Methods of Short-Growth Cycle Brassica chinensis L. Using IRMS and NIRS.

Seasonal (temporal) variations can influence the δ 13 C, δ 2 H, δ 18 O, and δ 15 N values and nutrient composition of organic (ORG), green (GRE), and conventional (CON) vegetables with a short growth cycle. Stable isotope ratio mass spectrometry (IRMS) and near-infrared spectroscopy (NIRS) combined with the partial least squares-discriminant analysis (PLS-DA) method were used to investigate seasonal effects on the identification of ORG, GRE, and CON Brassica chinensis L. samples ( BC s). The results showed that δ 15 N values had significant differences among the three cultivation methods and that δ 13 C, δ 2 H, and δ 18 O values were significantly higher in winter and spring and lower in summer. The NIR spectra were relatively clustered across seasons. Neither IRMS-PLS-DA nor NIRS-PLS-DA could effectively identify all BC cultivation methods due to seasonal effects, while IRMS-NIRS-PLS-DA combined with Norris smoothing and derivative pretreatment had better predictive abilities, with an 89.80% accuracy for ORG and BCs, 88.89% for ORG and GRE BC s, and 75.00% for GRE and CON BC s. The IRMS-NIRS-PLS-DA provided an effective and robust method to identify BC cultivation methods, integrating multi-seasonal differences.