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

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, T(0.5), T(1) and T(2)) 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 (EC(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, T(0.5), T(1) and T(2) treatments. Increasing salinity led to a rise in specific leaf area (SLA; cm(2) g(-1)) while it reduced leaf area (LA, m(2) per plant), leaf area ratio (LAR, cm(2) g(-1)), the unit leaf rate (ULR, gm(-2) per day) and water use efficiency (WUE g kg(-1)). The relative growth rate (RGR, gg(-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, cm(2) 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 (R(2) = 0.9847***), while between RGR and ULR the determination coefficient was also significant but lower (R(2) = 0.6808***). The most visible effect of the salinity treatment was on LA reduction. In T(0.5), T(1) and T(2) 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 T(0.5), T(1) and T(2) (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. (C) 2011 Elsevier B.V. All rights reserved.