Deficit Irrigation Strategies on young orange trees (cv Tarocco Sciara)

The economical sustainability of citrus orchards has to cope with the availability of water resources. One way to optimise water resources is to employ deficit irrigation (DI) strategies. DI effects on some physiological characters of young orange orchards were analysed. The orchard includes 300, 4-years old, plants located at the CRA-ACM experimental farm in Lentini, Sicily (37° 20 N; 14° 53 E). Four irrigation strategies were replicated 4 times: (i) Subsurface drip irrigation, supplying 75% IR (irrigation requirement), (ii) Partial root-zone drying, supplying 50% IR, (iii) Regulated deficit irrigation, supplying 50-100% IR, depending on crop phenological phases and (iv) Surface drip irrigation, supplying 100% IR. The IR was calculated using the Penman-Monteith approach, by assuming a crop coefficient of 0.45, and correction coefficients accounting for the localized irrigation. On selected plants, measurements of LAI, PAR, xylematic potential, canopy temperature, gas exchanges, trunk diameter and shoot number were carried out. Soil water content (SWC) was monitored by using Time (and Frequency) Domain Reflectometry. Preliminary results, obtained during the 2011 season, showed that: (i) xylematic potential and stomatal conductance were slightly variable between the investigated treatments with values quite below the stress condition, (ii) LAI and PAR were slightly variable between each plant and treatments, (iii) SWC was below the field capacity, (iv) trunk diameters were quite similar among the analysed plants.