Fertilization modifies the essential oil and physiology of basil varieties

Medicinal and aromatic crops are economically important because they are sources for secondary metabolites such as essential oils (EOs) and polyphenolic compounds. High biomass yields are obtained by conventional chemical fertilizers, whereas the production of EOs is more influenced by elicitors that act on secondary metabolic pathways. The objective of the field trials was to evaluate the effects of biologic and conventional fertilizers (biosolids: 40 and 20 t ha(-1), organic: 600 kg ha(-1), microorganisms (arbuscular mycorrhizal fungi, AMF): 60 kg ha(-1), chemical NPK 20-20-20: 300 kg ha(-1)) on plant growth, EO chemical profile and yield, and physiology of sweet basil (Ocimum basilicurn L.). The two sweet basil cultivars (varieties) used were the green -leafed `Aroma de Buzau' and the purple -leafed 'Violet de Buzau'. The greatest increases in fresh yields compared with unfertilized plants, 116% and 68% increases for the 'Aroma de Buzau' and 'Violet de Buzau, respectively, were obtained from the conventionally (chemical) fertilized plants. The 40 t ha(-1) biosolids treatment increased the EO content of the 'Aromat de Buzau' by 30%, while the AMF and organic treatments increased the EO content of the 'Violet de Buzau' by 21%. The major constituents of 'Aromat de Buzau', methyl chavicol and 13-linalool, were increased by 4 and 17% with the AMF and organic treatments, respectively. Eucalyptol and 8-guaiene concentrations in the EO were higher in the 40 t ha(-1) biosolids treatment, while T-cadinol and gamma-cadinene were higher in the 20 t ha(-1) biosolids treatment. For 'Violet de Buzau', the AMF treatment led to an increase of beta-linalool, limonene, and (+)-camphor, and decreased the concentration of methyl chavicol. The organic treatment increased the concentrations of limonene, (+)-camphor, terpinene-4-ol, and beta-caryophyllene, and decreased the concentration of methyl chavicol. The highest concentration of methyl chavicol was observed in the chemical fertilizer treatment. The 20 and 40 t ha(-1) biosolids treatments led to highest yields of eucalyptol, (+)-camphor, terpinene-4-ol, beta-caryophyllene, germacrene D, and tau-cadinol. The results demonstrated that conventional fertilizers can increase fresh yield while biological fertilizers positively alter the EO composition, leading to increased crop quality.