Spatial Variability of Soil Properties and Crop Responses in an Extended Citrus Area in Southern Italy

摘要

A field survey was carried out in a threeyear period in Sybaris Plain, an important citrus area of Calabria region in Southern Italy, to evaluate the spatial variability of physical and chemical characteristics of soil, nutritional status, yield and fruit quality responses of Clementine (Citrus Clementina Hort. ex Tan. ). Soils in the area interested by the survey were very heterogeneous, but five homogenous sub-zones were identified and described by means of soil drills and soil profiles. Eighty-four Clementine cv. ' Comune' orchards grafted on sour orange (C. aurantium L.)with similar age (15-20 years) were selected. The cultural practices were uniform according to regional extension service protocols. In each orchard several soil and crop characteristics were observed and recorded. Soil analyses were done at the beginning of the survey, whereas each year leaf and fruit quality analyses were performed. The data were processed using a multivariate approach. Discriminant analysis was applied with the aim to analyze simultaneously all data collected for every sampling unit, to verify the belonging to the sub-zone (group) and to individuate the variables that mainly influenced the discrimination between the groups. Two main discriminating functions were obtained, explaining about the 80% of the variability of the system. Moreover, the model allowed discriminating the 5 subzones, with a correct attribution to the groups of 100% of sampling units. Among soil physical-chemical parameters the variables with greater discriminant capacity were sand, silt, available phosphorous, total lime. Among fruit quality parameters, juice content, colour parameters and total acidity had a greater discriminating weight. Leaf nutritional status participated to discriminant function among groups mainly with Zn, Mn, P and K content.