Different strategies of deficit irrigation have been studied in an 11-year old citrus trees ( Citrus sinensis L. Osb. 'Navelina') grafted onto Carrizo citrange ( Citrus sinensis L. Osb. * Poncirus trifoliata L. Raf.). A sustained deficit irrigation (SDI) treatment was established, with a water supplied of 60% of the crop evapotranspiration (ET c); and a low-frequency deficit irrigation treatment (LFDI), watered according to the plant-water status. As a control a full irrigated at 100% of ET c was included. Midday stem water potential (Psi stem), stomatal conductance (g s), and micrometric trunk diameter fluctuations were measured during the maximum evapotranspirative demand period to evaluate the plant-water status, and to establish the main relationships between them. The seasonal pattern of the studied variables had a behavior consistent with the applied irrigation volumes. Significant relationships between Psi stem and g s, and the maximum daily shrinkage (MDS) were found. The lowest Psi stem and g s values were registered in the deficit treatments being the MDS significative higher in these treatments than in the control treatment. Yield response was highly influenced by irrigation strategy, being these results for LFDI significant better than SDI. Considering these results and the significant relationships between MDS and Psi stem, LFDI can be a sustainable deficit irrigation strategy, encouraging significant water savings without important impact on yield and fruit quality.
