Introduction: The limitation of freshwater resources is an important limitation in the growth and development of the plant, which affects the quantity and quality of production. On the other hand, the increasing population, the development of industries, the increase in cultivated area, and finally the decrease in precipitation, especially in arid and semi-arid regions, make the use of saline water in agriculture inevitable. Melon is a plant that is semi-tolerant to salinity, and different cultivars differ from each other in this respect, and this difference becomes more obvious in high salinities. This research was carried out with the aim of investigating the management of saline and conventional water consumption in late melon cultivation and its effects on the amount of sodium and potassium in plant organs, the physical characteristics of the produced fruit and its storability.
Materials and Methods: In order to investigate the content of elements sodium, potassium and the ratio of potassium to sodium in leaves, stems and roots and the quality of fresh and stored green melons irrigated with salt water, an experiment was conducted in split plot arrangement base on randomized complete block design in three replications at Torgh Mashhad Agricultural Research Station in 2020-2021 and 2021-2022. The main plot was the year and sub-plots was included different irrigation treatments: T1: control treatment, irrigation with fresh water (0.6 dS.m^-1), T2: irrigation with 3 dS.m^-1 salinity, T3: irrigation with 6 dS.m^-1  6 salinity, T4: irrigation with 3 dS.m^-1  salinity from 40 days after germination to harvest, T5: irrigation with 3 dS.m^-1  salinity from 20 days after germination to harvest, T6: irrigation with 6 dS.m^-1  salinity from 40 days after germination to harvest and T7: irrigation with 3 dS.m^-1  salinity from 20 days after germination to harvest.
Results and Discussion: The results of composite variation showed that the amount of sodium was increased by about 52%, 140% and 47% in the leaf, stem, and roots respectively, in comparison to control by application of T3 treatment. The stem had the greatest decrease in K/Na ratio in comparison to control by applied salinity irrigation, so the application of T3 treatment was decreased K/Na ratio in leaf, stem, and root about 40.2, 65.3, and 27.6 % in comparison to control respectively. The application of the T6 treatment had the lowest flesh weight to the whole fruit and the T5 treatment had the highest Brix of different parts of the fruit. The highest number of melons (9552  per ha^-1) and total yield (19.2 ton ha^-1) was obtained from the T1 treatment. Combining fresh water with high EC caused a further decrease in the number of melons and the total yield per hectare. Storing fruit for 14 days in cold storage did not have a significant effect on most of the measured traits, but the firmness of the fruit tissue showed a decrease of about 21% and the Brix of the fruit showed an increase of 4.3% in compare of first period in storage.
Conclusion: The use of irrigation water with less salinity in the early stages of the plant, such as the four-leaf stage and flowering time, although it caused better plant growth, but with the change (increase) in the salinity of the irrigation water, more stress was applied to the plant. The results showed that irrigation with saline water caused a cumulative increase in sodium and potassium content in leaves, stems and roots. Which was effective on changes in potassium to sodium ratio in root and stem plant. The results of the effect of salinity on the quality parameters of the fruit showed that the increase of salinity from 0.6 dS.m^-1 to 3 dS.m^-1 caused an increase in the flesh of the fruit to the total weight and Brix of the fruit in all three parts of the tip, middle and the end of the fruit, which indicates that the increase in salinity through the increase in sugar has an effect on the Brix value of the fruit. The results of the traits measured before and after two months of storage in cold storage showed that although applying salinity treatments did not have a significant effect on the firmness of the fruits, the firmness increased only up to a salinity of 3 dS.m-1, but during storage due to the effect environmental conditions and internal reactions of the fruit, the amount of firmness of the fruit decreased slightly and the amount of brix of different parts of the fruit increased significantly.