Saturday, 15 July 2006

Soil Suitability for the Cultivation of the "Mantuan" Pear (Lombardy, Italy).

Stefano Brenna, ERSAF, via Copernico 38, Milan, Italy and Lucio Andreoli, Provincia Mantova, via Alberto Mario 9, Mantova, Italy.

Lombardy (North Italy) is a Region which combines a vocation for the advanced industrial and tertiary sectors with modern agriculture and high productivity. However Lombardy is still rich in several typical agricultural products cultivated in specific areas, due to the particular pedoclimatic conditions and to the local tradition. The most well known case is that of wine: in Lombardy six main vineyard areas occur, where soil zoning is usually the base to address and differentiate the wine production. Nevertheless soil properties and qualities are of relevance to lead to the favorable environmental conditions characterizing the cultivated areas of other typical fruit and vegetables. This paper just deals with the soil information carried out to allow a local producer association to receive, according to the Reg. UE 92/2081, the recognition of Protected Geographical Indication (PGI) for the typical “Mantuan Pear”. The area concerned by the cultivation of the pear trees is located in the south-eastern corner of Lombardy (Mantua Province), mainly lying on Holocene, calcareous sediments of the Po river. To this purpose a soil suitability map has been provided by means of the interpretation of the georeferenced soil database at semidetailed scale (1:25,000 – 1:50,000) set up by ERSAF (Regional Agency for Agriculture and Forests) for the whole Lombardy plain (14,0000 km2). A specific soil survey and laboratory analysis have been also planned to integrate and complete the soil knowledge needed, especially with respect to the active calcium carbonate content. The criteria selected for the interpretation have been soil depth, active calcium carbonate content, particle size, drainage, water table depth and flooding risk, being ponding, excess of water within the profile and risk of chlorosis the main limitation factors for the pear trees growing. Finally the soils of the cultivation area concerned have been ranged in three classes: well suitable soils, moderately suitable soils and poorly suitable soils. The resulting soil suitability map shows that the best soils for the growth of pear trees are deep, loamy textured, well drained; they have a high available water capacity and a low active calcium carbonate content. Classified as Typic Ustifluvents or Fluventic Haplustepts those soils cover the 46% of the whole area and are mainly located on the levees of the alluvial plain. Fine (clay content ranging from 35 to 40%) and moderately-poorly drained soils, often with medium-high carbonate content and vertic features have been considered moderately suitable soils; they are classified as Vertic Ustifluvents or Calcic and Vertic Haplustepts and cover the 18% of the cultivation area. Poorly suitable soils instead cover the 36% of the area. They occur on: a) the concave and close depressions of the alluvial plain, where Vertisols and in general poorly drained very fine soils are present; b) the flooded bottom land along the Po river; c) the margin of the main level of the plain (Pleistocene Age) bordering the alluvial plain, where soils are more developed (Typic or Calcic Haplustalfs, Typic Calciustepts) but a strongly calcareous substrate together with an alkaline reaction (pH from 8,2 to 8,6) within 100 cm depth occurs. Since the 15th century pears were cultivated in the area and since that time they were crossed to produce increasingly tastier fruits. As the study pointed out yet, edaphic factors seem to be actually related to yield and fruit quality: moreover soil conditions in the “Mantuan Pear” cultivation district are strongly different from those of the surrounding territory, where pears are not and have never been cultivated. However the effect of soil qualities and behavior on the performance of high quality crops by the regulation of the genotype expression should be investigated more in the future.

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