Parametri di qualità del suolo in un oliveto lavorato e in uno abbandonato

The abandonment of olive orchards is a phenomenon of great importance triggered mainly by economic and social causes. The aim of this study was to investigate some chemical and microbiological parameters in a soil of a Southern olive grove abandoned since 1985, in order to define its level of fertility recovery. An adjacent rainfed olive grove having the same characteristics and managed according to extensive pract ices was taken as reference. Composite soil samples were taken in July 2010 from 0-20 and 20-40 cm layers. Soil quality recovery in the abandoned olive grove, triggered by the absence of soil and plant management, was evident. In fact, it showed values of soil organic matter, total N and pH significantly higher than those of cultivated orchard due to the natural input of organic matter (senescent leaves and branches of olive trees; weeds and shrubs; roots; root exudates) and the absence of tillage; on the contrary, available P was lower because it was probably used by the considerable spontaneous vegetation for nutritional aims. Microbial counts showed fewer total bacteria and fungi in the abandoned grove which also showed a greater number of cellulolytic bacteria. The activities of some enzymes involved in the carbon cycle were higher in soil sampled from the abandoned orchard because of the consistent organic matter input; particularly, the high ?-glucosidase activity placed soil from abandoned grove in an advanced evolutionary stage. The study of the carbon substrate utilization profiles using Biolog® method revealed a higher microbial diversity and complexity in soil taken from the cultivated orchard. It seems that, under our experimental conditions, the extensive techniques used did not affect microbiological fertility of the cultivated soil.