Influence of soil on oregano (Lippia graveolens Kunth.) essential oil chemotypes from two regions of Saucillo, Chihuahua

Abstract

Objective: This study aimed to assess the association between soil properties, chemotypic expression, and essential oil (EO) yield in Lippia graveolens Kunth (Mexican oregano) from two distinct regions in Saucillo, Chihuahua. Design/Methodology/Approach: A comparative analysis was conducted at two sites: a wild population established on Chernozem soil (Carboneros) and a cultivated population grown on Vertisol (Subida Alta). Soil characterization followed NOM-021-SEMARNAT guidelines, including texture, pH, electrical conductivity (EC), organic matter (OM), carbonates, and available nutrients. Essential oil yield was quantified via hydrodistillation using a Clevenger apparatus, while volatile compound profiling was performed through gas chromatography–mass spectrometry (GC–MS) following steam distillation. Statistical differences between sites were evaluated using ANOVA and t-tests (α = 0.05) with SAS 9.4 software. Results: The wild population site featured a higher clay content, increased OM, and a slightly alkaline pH (7.88), correlating with a chemotype enriched in aromatic precursors (p-cymene 25.04%; γ-terpinene 9.46%). In contrast, the cultivated site exhibited a sandy-loam texture, reduced OM, a more alkaline pH (8.04), elevated levels of available potassium (K⁺), and a predominance of phenolic monoterpenes (carvacrol 29.15%; thymol 10.27%). EO yield was 3.53% at the wild site and 3.00% at the cultivated site. Variations in texture, pH, OM, and K⁺ content were consistent with a transition from precursor-rich profiles to phenolic compound-dominated profiles. Limitations/Implications: The study's scope was constrained by the absence of controlled variables, such as genotype and agronomic history, due to the wild nature of oregano populations. Additionally, extraction techniques may have influenced both EO yield and chemical profiles observed via GC–MS. Experimental manipulation of soil parameters would enhance reproducibility and strengthen causal inferences. Findings/Conclusions: The findings suggest that soil characteristics significantly influence chemotypic expression in L. graveolens. Finer-textured soils with higher OM content favored the accumulation of p-cymene and γ-terpinene, whereas sandy-loam, alkaline soils with increased K⁺ availability were associated with higher concentrations of carvacrol and thymol.