Melon crops (Cucumis melo L., cv. Tendral) grown in a mediterranean environment under saline–sodic conditions: Part II. Growth analysis

Abstract

Abstract An irrigation experiment using saline–sodic waters was carried out in 2004 in the Volturno river plain (southern Italy) to investigate the growth of the melon cultivar Tendral under saline–sodic conditions. Four salinity irrigation treatments (C, T0.5, T1 and T2) were tested using water with electrical conductivities of 0.9, 8.7, 15.3 and 28.2 dS m−1, respectively. At the end of the crop cycle the electrical conductivity ( E C e d ) of the saturated paste in the soil profile between 0.0 and 0.9 m reached values of 0.9, 3.2 4.2 and 6.6 dS m−1, respectively, for the C, T0.5, T1 and T2 treatments. Increasing salinity led to a rise in specific leaf area (SLA; cm2 g−1) while it reduced leaf area (LA, m2 per plant), leaf area ratio (LAR, cm2 g−1), the unit leaf rate (ULR, g m−2 per day) and water use efficiency (WUE g kg−1). The relative growth rate (RGR, g g−1 per day) and the biomass produced (W, g plant−1) decreased. The reduction in RGR was closely related to the reduction in relative leaf area growth rate (RLAGR, cm2 of leaf cm−2 per day), the relative leaf weight growth rate (RLWGR, g of leaf g−1 per day) and the relative fruit weight growth rate (RFWGR, g of fruit g−1 per day). A highly significant positive correlation was found between RGR and LAR (R2 = 0.9847***), while between RGR and ULR the determination coefficient was also significant but lower (R2 = 0.6808***). The most visible effect of the salinity treatment was on LA reduction. In T0.5, T1 and T2 the LA was respectively 10%, 34% and 45% less than in the C treatment. W and the crop evapotranspiration (ETc) also decreased with increasing salinity. The reduction in W for T0.5, T1 and T2 (respectively, 2%, 28% and 40% less than treatment C) was greater than the reduction in ETc (respectively, 2%, 22% and 32% less than treatment C). Therefore also the WUE significantly decreased as salinity increased. The Tendral cv. responded to salinity mainly with morphological adaptations, first with a LA reduction that was followed by decreases in the W and ETc. There may well also be functional adaptations associated with ULR reduction.