PRELIMINARY RESULTS ON THE EFFECTS OF PARTIAL ROOTZONE DRYING, REGULATED DEFICIT IRRIGATION AND SUSTAINED DEFICIT IRRIGATION ON 'VERMENTINO' GRAPEVINE IN SARDINIA (ITALY)

In a two-year trial (2006-2007), Sardinian ‘Vermentino’ native grapevines were irrigated according to different irrigation strategies: Full Irrigation (FI, control), Partial Root-zone Drying (PRD), Regulated Deficit Irrigation (RDI), Sustained Deficit Irrigation (SDI) and Farmer’s aid-irrigation management (FIM). A randomized block design was carried out using irrigation treatments (FI, RDI, SDI, FIM and PRD) as controlled variability factor. Qualitative and quantitative production parameters were determined and plant water stress indicators, i.e. Maximum Daily Shrinkage (MDS) and midday Stem Water Potential (mSWP), were monitored. The main results showed that RDI and SDI water-saving irrigation strategies significantly improved must quality, without the expected sensible reduction of plant productivity, in comparison with FI. The PRD treatment reduced yield in the first year, but increased it in the second year, compared to control (FI). The severe water reduction of the FIM treatment induced a strong yield reduction and must quality worsening, especially in the first year. The MDS was a more powerful plant water stress indicator than the mSWP. The SDI treatment gave the highest water-use efficiency in both years.