Green manure and water consumption in Southern Italy orchards

The research was carried out in Southern Italy (Basilicata Region), on a mature table grape vineyard and a young peach orchard located in two different sites, green manured with a fall/winter Vicia faba and Avena sativa mixture. In each orchard, two different plots were established. One was cover cropped in the inter-row strip (Green Manure plot, GM), while the other one was managed according to the ordinary fertilization and tillage techniques (Mineral Fertilization plot, MF), normally used by the growers of the two areas. At springtime, when the cover crops were buried, soil water content was measured at 10 to 90 cm depth. The soil water content of the GM plots was lower than that of the MF plots, showing a deficit of about 80 mm in the peach orchard and 40 mm in the vineyard. The results obtained from the trials suggest that: a. Cover crops can affect water content of the soil, by causing a consistent depletion of its moisture, even in deep soil layers. b. In soils interested by green manure it is necessary to start earlier with irrigation, especially in dry years, in order to avoid dangerous water stresses due to the strong water uptake exerted by the cover crops, occurring during their intense vegetative growth phase. c. The utilization and feasibility of the cover crops in semi arid environments must be evaluated on a single case basis.