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The research was carried out in a warm-arid area of Southern Italy (Basilicata region) on two peach orchards managed using different agronomic practices (green manuring and inorganic fertilisation). In November 1994, microbial biomass C, soluble organic C, total organic C and total N were evaluated in soils two years after planting. Trunk diameter and leaf area were measured in the two treatments. In 1996, the evolution of mineral nitrogen concentrations was monitored after cover crop (Vicia faba and Avena sativa) incorporation. The same material was the objet of experiments conducted under controlled conditions in the laboratory.

The green manured soil in the field showed significantly higher values of microbial and soluble C than the inorganic fertilised one. Cover crop incorporation induced lesser tree vegetative growth. Green manuring ensured a sufficient supply of mineral nitrogen at the time of greatest demand by the peach trees (one month after bloom).

In laboratory, under controlled conditions, incorporation of Vicia faba alone made for highest mineral nitrogen levels. It is suggested that the mineralisation process could be regulated by varying the specific composition of the cover crops.