Abstract: In order to study the effect of nitrogen spray at different times on color and yield parameters of grape cv. Pykany, an experiment was carried out in factorial based on randomized complete block design with four replications in Khalil Abad County in 2015. The treatments included three concentrations of nitrogen (0, 5 and 10 ppm) and three spray times (Late April, before bloom stage, and after pollination and fruit set stage). Color parameters such as brightness rate (L), redness (a) and yellowness (b), chroma, hue angle and browning index were evaluated in this experiment. The results of variance analysis and means comparison showed that the effect of treatment containing spray at concentration of 10 ppm on yield was significant at 1%. There were not significant differences among treatments of urea concentrations and spray times on L and b but different concentrations of urea had significant effect on a* at the level of 1%, so that the highest amount of significant difference was due to the treatment of urea spray at the concentration of 10 ppm and the lowest amount was due to the control treatment. Furthermore, the interaction effect of concentration and different times of nitrogen application on color intensity index was significant at the level of 5%. Based on the results, the effect of different concentrations of urea spray on hue angle was significant at 1% so that the highest level of significant difference was due to the concentration of 10 ppm and the lowest was related to control treatment.

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