We evaluated the osmotic adjustment capacity of leaves and roots of young olive (Olea europaea L.) trees during a period of water deficit and subsequent rewatering. The trials were carried out in Basilicata (40 degrees 24' N, 16 degrees 48' E) on 2-year-old self-rooted olive plants (cv. 'Coratina'). Plants were subjected to one of four drought treatments. After 13 days of drought, plants reached mean predawn leaf water potentials of -0.45 +/- 0.015 MPa (control), -1.65 +/- 0.021 (low stress), -3.25 +/- 0.035 (medium stress) and -5.35 +/- 0.027 MPa (high stress). Total osmotic adjustment increased with increasing severity of drought stress. Trees in the high stress treatment showed total osmotic adjustments ranging between 2.4 MPa at 0500 h and 3.8 MPa at 1800 h on the last day of the drought period. Osmotic adjustment allowed the leaves to reach leaf water potentials of about -7.0 MPa. Active osmotic adjustment at predawn decreased during the rewatering period in both leaves and roots. Stomatal conductance and net photosynthetic rate declined with increasing drought stress. Osmotic adjustment in olive trees was associated with active and passive osmotic regulation of drought tolerance, providing an important mechanism for avoiding water loss.

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The aim of the present work was to evaluate the effects of regulated deficit irrigation (RDI) applied in the post-harvest stage of peach\ud trees. The 3-year trial was carried out in Italy (N 4020¢, E 1648¢) on mature peach plants (cv ‘‘Springcrest’’) trained to transverse Y. From bud break to harvest, irrigation was carried out by applying 100% ETc, while from harvest to early autumn, plants were separated into three groups and subjected to different irrigation treatments (100, 57 and 34% ETc). The decrease in soil water content caused a reduction in the values of tissue water potential and gas exchange both in 57%\ud ETc and 34% ETc treatments. RDI determined the reduction in the growth of waterspouts and lateral shoots but did not influence the growth of fruiting shoots. During the trial, no significant reductions in crop yield and quality were observed in the 57% ETc treatment, whereas about 1,100, 1,800 and 2,500 m3 ha–1 of water were saved in the first, the second and the third year, respectively. In the second year of the trial, the use of RDI in the post-harvest stage determined\ud carbohydrate and nitrogen accumulation in roots, branches, shoots and floral buds. The results demonstrate that, under scarce water supply conditions, a clear benefit can be obtained through the use of RDI during the post-harvest stage. This confirms the possibility to reduce the irrigation water by applying RDI during phenological stages less sensitive to water deficit without negatively affecting peach growth and yield

This 4-year on-farm study reports the effects of different agricultural practices on yield and soil organic carbon (SOC) in kiwifruit and apricot orchards grown in a Mediterranean area. Groups of plants under local orchard management (LOM,x) practices (i.e. soil tillage, removing of pruning residues and mineral fertilisers) were compared with plots under soil-protecting orchard management (SPOM) actions (i.e. cover crop, no-tillage, compost application and mulching of pruning residues). In the SPOM blocks fertilisation rate was based on plant demand and irrigation volumes calculated on the evapotranspiration values, while they were empirically calculated in the LOM plots. Results show that yield was 28–50 per cent enhanced by SPOM practices while SOC remained close to the initial values. In comparison with LOM plots, changed practices increased up to 28–90 per cent the amount of P and K, and 13 per cent that of N annually incorporated into soil increasing their reservoir in the soil. The study demonstrates that appropriate land management can increase the mean annual carbon soil inputs from about 15 to 90 t ha1 per year