Abstract:
Soil properties are major factors that impact Turmeric (Curcuma longa L., Zingiberaceae) growth and quality. The Thai Herbal Pharmacopoeia (THP) recommended that dried turmeric should contain not less than 5.0% w/w of total curcuminoids (TC) content. The effect of soil properties on extraction yields and TC contents of turmeric rhizomes was investigated in this study. Twenty-three samples of turmeric rhizome and soils were collected in various cultivation site in Chiang Rai, Thailand. Clustering analysis was used and three group clusters were found; C1, C2, and C3. Two turmeric cultivars; Trang1 (T1) and Trang 84-2 (T84-2) were cultivated in these areas. C1 cultivated both T1 and T84-2 with highest soil pH (4.642±0.802). C2 cultivated exclusively T84-2 with high soil potassium (K) (1821.43 ± 533.63 mg/kg), and C3 cultivated exclusively T1 with high soil calcium (1941.93 ± 686.52 mg/kg). T-test and Principal Component Analysis (PCA) were utilized and found that turmeric qualities between two cultivars was significantly different, with T1 having a higher % yield (p-value = 0.0014), % total curcuminoid (p-value = 0.0131), and % bisdemethoxycurcumin (BDMC) (p-value = 0.001). Pearson correlation analysis was used to find a relationship between soil properties and turmeric qualities. T1 was found having consistent turmeric qualities compared T84-2, which reacted negatively to various soil properties in this study (r<-0.4). This study can be used to understanding the characteristic of turmeric cultivar for managing the extraction yield of turmeric rhizomes by adjusting the soil properties appropriated for each turmeric cultivar.
