Development of a plant-based RDI strategy for almond in semi-arid area of Apulia (Italy): preliminary results of Almond Management Innovation (Amì) project.

Water scarcity is becoming the most serious problem affecting semi-arid areas. During the hottest and driest months increasing water withdrawal could be impossible and dangerous due to sea water intrusion into the aquifers. The Almond Management Innovation project aims at improving the innovation along the whole almond chain getting its production more economically and environmentally sustainable. This study aims at developing a Regulated Deficit Irrigation (RDI) strategy based on the monitoring of tree functionality and its physiological needs. Trees of Guara cultivar were irrigated maintaining midday stem water potential (Ψs) at about -1.0MPa till reaching the final fruit size (beginning of kernel filling). Afterward three water restrictions were imposed till the hull splitting: CTRL, mRDI, sRDI maintaining Ψs at -1.2, -1.5 and -1.9 MPa, respectively. The treatments were compared for leaf functionality, fruit growth, yield and water productivity. 2021 was particularly dry and hot during the summer period. At the end of the irrigation season water supply was reduced of 15 and 25% in mRDI and sRDI, respectively; focusing on the kernel filling period the reduction increased at 20 and 37%. During this period leaf net photosynthesis and stomatal conductance were lower in mRDI followed by sRDI. Volume and dry weight of fruits and seeds were similar as well as yield (1.2tha-1) but sRDI showed a higher number of tight-hull fruits. The highest water productivity was recorded in sRDI followed by mRDI and CTRL. These preliminary results suggest that managing RDI by means of plant-based indicators could be useful for saving water not affecting the yield of the current year. Further investigations are needed to: identify a pool of reliable and quick to measure plant-based indicators; study the role of the stored carbohydrate on kernel filling stage; evaluate the effect of the current water shortage on the next year performance.