A methodology proposal for olive zoning. A case study in the Cilento area.

1. A methodology proposal for olive zoning. A case study in the Cilento area. University of Naples Federico II De Marco E.*, D’Urso G.*, Langella G.‡, Savarese M.§, Parisini C.§, Sacchi R.†§ *University of Naples Federico II, Department of Agricultural Engineering and Agronomy, via Università 100, 80055 Portici (NA), Italy ‡ University of Naples Federico II, Department of Soil, Plant and Environmental Sciences, via Università 100, 80055 Portici (NA), Italy § CRIOL, Centro Ricerche per l’Industria Olearia, Industria Olearia Biagio Mataluni, zona industriale, 82016 Montesarchio (BN), Italy † University of Naples Federico II, Department of Food Science, via Università 100, 80055 Portici (NA), Italy e-mail: edemarco@unina.it INTRODUCTION MATERIALS AND METHODS During the last decades researchers have been focusing increasing interest on the influence exerted by the growing environment on quality and typicity of agro-food products. Knowledge of the complex relations between product and environment is important to improve the agronomic management and to orient land management choices. This knowledge is particularly advanced for grape. During the last decades the aptitude of different zones to grape cultivation has been object of several interdisciplinary studies, while little study has been carried out in this field for olive. • 14 experimental sites (rainfed adult monovarietal olive orchards) were selected in the Cilento area and were characterized as regards soil, climate, hydrologic balance, plant parameters and fruit characteristics. • SOIL • Sampling: by means of a soil auger, near to the trees were olive samples were collected • Pedological characterization: major soil horizons were identified • Physical characteristics: texture (MIRAAF 1994) was determined for each soil horizon • Chemical characteristics: pH, electrical conductivity, organic matter, total CaCO3, cation exchange capacity, exchangeable cations, Fe, Al, Si and Mn extracted by ammonium oxalate and dithionite-citrate were determined for each soil horizon (MIRAAF 1994) • CLIMATE • Air temperature and precipitation: inferred from daily data collected in meteorological stations near to the experimental sites and kindly provided by Campania Region and by Consorzio di Bonifica Velia. • Daily global radiation: calculated for each site from latitude, slope, aspect and atmospheric transmittance (Dingman, 2002) • Daily reference evapotranspiration: calculated using Makkink radiation method • Crop coefficients: obtained dividing Penman-Monteith potential evapotranspiration by reference evapotranspiration • ORCHARD • Leaf Area Index (LAI): obtained by processing hemispherical images taken by a camera with fish-eye lens form beneath the canopy. • FRUIT • Sampling: in different dates (form October to December 2005) in order to reduce the differences in fruit ripening between sites. • Weight & diameter • Dacus oleae infestation • Ripeness Index (RI) • Water & oil content • Fatty acid composition, determined by GC analysis • Phenolic fraction: obtained by solvent extraction from olive pulp, characterized (qualitatively and quantitatively) by reversed-phase HPLC analysis, confirming the identification by LC-MS analysis OBJECTIVES This work is aimed to propose a methodology for an olive zoning in order to obtain good quality final products, focusing the attention on a traditional olive cultivation area located in the National Park of Cilento and Vallo di Diano (Campania region, Italy) and on a local widespread olive (Olea europaea L.) cultivar (Pisciottana). This methodology should satisfy different requirements: it should integrate knowledge across different disciplinary fields, it should be physically-based and easy-to-use, so that it might be applied also for different areas and genotypes without requirement for substantial human and material resources. ESTIMATE OF LEAF AREA INDEX BY HEMISPHERICAL PHOTOGRAPHY Hemispherical images relative to two experimental sites differing widely in their values of Soil Cover. RESULTS Hemispherical images were processed with the software CAN_EYE (INRA-CSE, Avignon, France), which derives canopy characteristics, such as LAI, form the measurement of the gap fraction, i.e. the transmittance of light through the canopy considering the vegetation elements as opaque (Jonckheere et al., 2004; Weiss et al., 2004). RI resulted to be negatively correlated with latitude (Pearson correlation coefficient r = -0,88), altitude (r = -0,59), slope (r = -0,53) and LAI (r = -0,67) and positively correlated with mean annual temperature (r = 0,71). These relations could be attributed to the influence of temperature and solar radiation on fruit pigmentation. In the orchards characterized by high slope and LAI, fruits receive less solar radiation and consequently their ripeness proceed slowly. Literature data confirm the significant influence exerted by fruit shading on RI and fruit dimension (Tombesi et al., 1998). As RI, also fruit dimension and weight were correlated negatively with altitude, slope and LAI and positively with global solar radiation. Pixel classification with the software CAN_EYE As regards fatty acid composition, unsaturation degree proved to be affected by the thermal regime, as confirmed in literature (Harwood et al., 1994); oleic/palmitic acid ratio was negatively correlated with mean annual air temperature (Figure 1). Gap fraction estimated for each of the angular sectors in which the image is divided Figure 1.Oleic/palmitic acid ratio of the lipid fraction of olive pulp as a function of mean annual air temperature. Loof-up-table (LUT) Leaf Area Index Minimization of the error between gap fraction from LUT and measured gap fraction Hydrologic balance simulations gave, among other outputs, daily values of potential (Tp) and actual transpiration (Ta). Ta/Tp ratio was used as water stress index. Great difference was observed among sites as regards Ta/Tp evolution during year (Figure 3). However, simulated water stress resulted to be strictly influenced by crop parameters, in particular by LAI, rather than by climate and soil parameters. As regards the phenolic fraction, a strong negative correlation was observed between total phenol content and LAI (Figure 2). This result could be explained as a positive effect of solar irradiance on biophenol synthesis. The lower part of the canopy receives less solar radiation in the orchards characterized by greater vegetation thickness, resulting probably in lower phenol content of the fruits. A positive influence of various stress agents, among which water stress and solar irradiance, on the synthesis of phenylalanine ammonium lyase, a key enzyme in biophenol synthesis, has been reported in literature for different plant species (Chalker-Scott et al.,1989). Figure 3. Evolution during year of simulated actual to potential transpiration ratio for each experimental site. Figure 2. Relation between total phenol content of olive pulp and Leaf Area Index of the orchard. At a comprehensive analysis, a clear differentiation can be observed between the experimental sites as regards soil and climate parameters and, as a consequence, fruit characteristics. The Principal Component Analysis carried out on data concerning the experimental sites and the respective fruit samples (Figure 4) shows that sites 11, 12 and 13, characterized by higher altitude and slope, lower temperature and radiation, higher LAI, turn out to have later maturation, smaller fruits and lower phenol content of the fruits than all the other sites. Sites 15, 18 and 19 are in the opposite condition. CONCLUSIONS Relevant influence of agronomic management (particularly LAI) on olive quality. Site topography (altitude, slope, aspect) as not negligible factor. Lower influence exerted by soil characteristics. Important contribution of solar radiation fluxes to the ripening processes and to the synthesis of olive minor components. Optimization of agronomic management as priority target. Relations between climatic and pedological factors and olive productive results to be investigated in depth (in particular, influence of solar radiation on the synthesis process of phenolic compounds). Figure 4.Principal Component Analysis carried out on data regarding site characteristics (soil, climate, topography, LAI) and olive characteristics and composition. REFERENCES Chalker-Scott L., Fuchigami L.H., 1989. The role of phenolic compounds in plant stress responses. In: Low-temperature Stress Physiology in Crops, Ed. by Paul H.L. CRC Press, Boca Raton, FL, pp. 27-40. Dingman S.L., 2002. Physical Hydrology (2nd edition). Prentice Hall, New Jersey, pp. 646. Harwood J.L., Jones A.L., Perry H.J., Rutter A.J., Smith K.L., Williams M., 1994. Changes in plant lipids during temperature adaptation. 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