Melon crops (Cucumis melo L., cv. Tendral) grown in a mediterranean environment under saline-sodic conditions: Part I. Yield and quality

Melon plants (Cucumis melo L.) cv. Tendral were grown in an open field trial in 2004 to investigate the effect of increased saline sodic water concentration on yield, crop tolerance, fruit quality and ion content. Three saline water concentrations were created by adding 5, 10 and 20 g l-1 of commercial sea salt (NaCl) to well water. These treatments were compared against well water (C) with an electrical conductivity (ECw) of 0.9 dS m-1. The ECw of the saline water was 8.7, 15.3, and 28.2 dS m-1 for treatments T0.5, T1 and T2, respectively. The experimental field was used between 1995 and 2001 for trials that studied the effects of saline irrigation on crop yield responses. Later, between 2002 and 2003, the same field was irrigated by well water. Increased salinity significantly reduced the leaf area index (LAI) and leaf area duration (LAD) for both vegetative growth and fructification, whereas the net assimilation rate (NAR) was reduced only during vegetative growth. Yield reduction resulted from the number and average weight of the marketable fruit. The maximum mean seasonal electrical conductivity of a saturated soil paste without yield reduction (i.e., the salt tolerance threshold) was 1.73 and 1.54 dS m-1 for the total yield and the marketable yield, respectively. Above the salt tolerance threshold, the total yield was reduced, per unit increase of soil salinity, by 14%, and the marketable yield by 15%. The salinity positively affected the refractometric degree. Preservability was moderate in treatments C, T0.5 and T1, whereas it was good for treatment T2. There were significantly fewer rotten fruit in T2 than in treatments C, T0.5 and T1. The salinity treatments increased the Na concentration in the leaves and stems; Na concentration decreased from the basal to apical part of the plant (for both leaves and stems). In addition, the maintenance of K selectivity in both plant parts could be a strategy used by the plants for increasing their salt tolerance and enhancing fruit quality (TSS).