Pedologic parameters related to yield and quality of bergamot oil

The effect of some pedologic parameters on the yield and chemical compositi on (quality) of oil from bergamot (Citrus bergamia Risso) fruits is reporte d. Throughout the 3-year trials in 25 bergamot groves, pedoclimatically rep resentative of the area of cultivation, soil was sampled to assess chemical -physical parameters while fruits were sampled to determine oil yield and q uality. The data collected were defined in curvilinear regressions in which pedologic parameters were the independent variable and yield and volatile oil components were the dependent variable. Results showed that the size an d distribution of soil particles (texture) directly affected yield and the constituents mainly responsible for the "bouquet" of bergamot oil. A high s and component exerted a negative influence by lowering the percentage of li nalool and linalyl acetate but increase the limonene content, which is only marginally responsible for fragrance. Silt and clay had the opposite effec ts. Interactions between the chemical constituents of soil and oil yield an d quality were minimal. No correlation with organic matter, total nitrogen (N), or exchangeable potassium (K) was determined. Available phosphorus (P) seemed to affect only some of the minor oil constituents (beta-pinene, myr cene and beta-caryophyllene). Total CaCO3, pH, and Mg positively influenced oil yield and quality. Calcium (Ca) was directly and positively related to linalool alone. In summary, soil and irrigation management became essentia l in yield and quality of bergamot oil. These results should be considered in view of the predominantly sandy matrix of Italian bergamot-growing zone.