Soil fertility comparison among organic and conventional managed citrus orchards in Sicily.

In recents years, organic farming is expanding in Southern Italy and in the Mediterranean area, due to interest of consumers and EU agricultural policies. Evaluation of organic farming system introduction on soil quality and fertility status should be taken into account in order to define medium-long term environmental and agricultural strategies, on both locol and national scale. Soil physical, chemical and biological parameters represent effective tools to evaluate soil quality and changes in soil fertility status, as a consequence of different agronomic management (i.e. organic vs coventional). The aim of this work was to compare soil fertility of conventional and organic managed citrus Orchards, using specific soil system descriptors. The research was carried out in a Mediterranean environment (Sicil Region, Southern Italy), on Navelina and Tarocco orchards. Soil characteristics were analysed in 54 farms under both organic and conventional management. Farms were selected to obtain similar pairs (27) in the same environmental conditions. Moreover, orchards pairs were homogeneous for age, cultivar and rootsock to reduce effects not linked to soil management. For each soil, total organic carbon, total nitrogen, mineral NO3-N and NH4-N were determined. In addition, in order to evaluate biological fertility of the considered soils, carbon mineralisation and nitrogen mineralisation in anaerobic conditions were studied. Soils' humic fraction was at least characterised qualitatively by isoelectric focusing technique,to obtain information on soil organic matter stability. Potenzially mineralisable carbon and cumulative mineralised carbon determined on 21 days experimental trials differed significantly in organic and conventional soils. Since this significance was detected also for cumulative mineralised carbon after 7 days, probably C-mineralisation represents the more reliable and prompter indicator to discriminate soil biological fertility with respect to the other tested ones. Moreover, it should be remarked that some parameters (as total nitrogen content, mineralised carbon after 1 days and the more humified organic matter fraction), even if not yet significantly different, revealed a strong tendency to increase in organic managed soils, attesting that the organic citrus orchards can be considered systems able to conserve energy and store nutrients more than the conventional ones

Quality assessment of citrus-processing industry waste compost for organic and conventional farming

The aim of the work was to verify the potential of citrus by-products for the production of a quality compost to be used in both conventional and organic farming. Two different composts were produced utilizing Pastazzo (mixture of citrus pulp and skins). One of them, to be used in conventional farming, was prepared adding sludges obtained from citrus industry waste water treatment to pastazzo. The other one, whose final destination was organic farming, was produced without the addition of sludge as starting raw material. Chemical parameters were used to evaluate the characteristics of the final product. Results obtained demonstrated that organic residues from citrus-processing industry could be considered as raw materials for the production of quality composts for both conventional and organic farming