الفهرس 
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Abstract
Spraying potato plants with melatonin or treated soil with hydrogel increased the number and weight of large tubers /plant. Whereas melatonin was significantly more effective. Also, a significant effect was noted as the interaction between irrigation intervals treatments and treated plants.
Overall results of the present study showed that the highest values were obtained with those plants which sprayed with melatonin at highest concentration and irrigated plants each 10 days, in both seasons. While the lowest values were observed with those plants which were untreated (control plants) and irrigated every 20 days.
The highest values of number and weight of medium size of potato tuber were obtained from potato plants which irrigated at 10 days interval. The results of current experiment showed that the use of hydrogel or melatonin showed significant increase in number and weight of medium size tuber/plant within both seasons.
The longest irrigation intervals showed the highest values of both number and weight of small tubers/plant in the second season only. A decrease of number and weight of small tubers per plant in both seasons in plants treated with melatonin but not with hydrogel. Regarding the concentration effects, our results showed that the differences between control plants and highest concentration were significant in both seasons. Where’s treated plants with high concentration led to a decrease in the number of small tubers /plants.
The height of potato plants was affected significantly with irrigation regime. Irrigation every 10 days showed the highest values of plant height in the first season, while in the second season insignificant differences were detected. Also, our results showed that spraying potato plants with melatonin was more effective in increasing plant height significantly, in both seasons. The highest concentration of hydrogel or melatonin showed the best effect to improve plant height in both seasons.
The results of our current experiment showed that irrigation every 10 days in both seasons significantly increased the total tuber weight /plant. Regarding the same value of total tuber weight/ plant, melatonin showed greater effect. A concentration-dependent effect was also noted in both seasons.
The results of the current trial also showed that increasing the intervals of irrigation up to 20 days markedly decreased the total yield expressed as ton/feddan in both planting seasons. Increasing the concentration of both hydrogel and melatonin had a positive relationship with total yield.
Our results showed that the short interval irrigation regime was more significant in fresh total weight/ plant. Additionally, both hydrogel and melatonin treatments had increased the fresh total weight with a marked significance with melatonin. Increasing traits concentrations were positive in relation with fresh weight/ plant.
The highest values of dry weight g/plant were obtained with the narrow intervals of irrigation. Statistics show that these treatments showed significant effects on this trait and melatonin showed higher values of dry weight g/plant at the highest concentration.
Our results showed that the irrigation every 10 days resulted in a slightly higher percentage of dry matter in both seasons. Melatonin spraying was more effective in increasing potato dry matter percentage as compared to control. Also, the highest concentration of either hydrogel or melatonin showed the highest dry matter percentage.
In contrast, irrigation with 20 days intervals showed the higher values of specific gravity/tuber in both seasons. Spraying plants with melatonin was superior in specific gravity effect and showed the highest values. The highest concentration of both traits obtains the highest values of specific gravity value in both planting seasons.
It’s clear from the data obtained from this experiment that water applied for potato crops was decreased with the irrigation regime of 10 days interval in both seasons. The hydrogel or melatonin trend decreased the amount of water applied to potato crop. About 60% of conventional water was required as hydrogel or melatonin is used.
The average quantity of water applied m3/fed was lower with those plants which irrigated each 20 days in compare with those plants which irrigated each 10 days, but with regarding to the correlation between these quantities of water and total yield of potato as ton/fed or kg/plant it is clear that irrigate each 10 days was better in compare with irrigate each 20 days.
On the other hand, application of hydrogel or melatonin treatments data show that average quantity of water applied resulted in saving water and improved its correlation with total yield (kg /plant).
These results reflect how much irrigation water can be saved when the experiment treatment is applied with growers and farmers in applied fields.
Water use efficiency was increased with using melatonin at higher concentrations in compare with either using lower concentrations of melatonin or hydrogel when added to the soil before planting at the highest rate.
In conclusion, this study showed that irrigation regime is every 10 days which starts after 30 days from sowing and hydrogel treatment at 5.0kg /fed. as soil additive pre-planting potato plants foliar treated with melatonin (150ppm) two times at 45 and 60 days from planting enhanced plant growth, potato tuber productivity and water use efficiency. This treatment could be recommended for application to potato fields under quite similar environmental conditions.