Document Type : Research Paper

Authors

• Ehsan Kahneh ¹
• Samar Ramzi ¹
• Koroosh Falakro ²

¹ Department of Technology and Production Management, Tea Research Center, Horticultural Science Research Institute, AREEO, Lahijan, Iran

² Department of Genetic and Plant Breeding, Tea Research Center, Horticultural Science Research Institute, AREEO, Lahijan, Iran

Abstract

Background and objectives: Color is one of the most important factors in determining the quality of tea, and it is directly influenced by the vegetative and environmental conditions of the plant, including rainfall, fertilizers, and light. Light, as one of the key environmental variables, serves as the primary factor influencing plant color by providing the energy necessary to regulate plant growth. Tea is a shade-loving plant, and reduced light can enhance the quality of the tea beverage by decreasing or slowing the formation of photosynthetic inhibitors. Consequently, the use of various tea plant shading methods to produce high-quality and high-value green tea is increasing in tea-growing regions worldwide.
Methodology: This research aims to investigate the effects of nitrogen fertilizer and light intensity on the quality of green tea leaves. The experiment was conducted as a split-plot in time within a CRBD design, with treatments including: (1) unshaded plants + 250 kg/ha of urea;
(2) unshaded plants + 500 kg/ha of urea; (3) 50% shading + 250 kg/ha of urea; (4) 50% shading + 500 kg/ha of urea; (5) 90% shading + 250 kg/ha of urea; and (6) 90% shading + 500 kg/ha of urea, implemented in three replications. Each replication measured 6 × 0.7 meters, and shading was applied during the spring and summer harvests. Greenhouse shade nets of 50% and 90% density were used as covers. The nets were placed over the bushes for three weeks, ensuring that the sides were also fully covered and secured with rope. After the designated period, the shades were removed, and leaf picking was performed. In each harvest, yield (one bud and two leaves) and yield components, including shoot density and weight, chlorophyll content, concentrations of N, P, and K nutrients, and several biochemical characteristics, were measured in the harvested green leaves.
Results: Using 50% shade with 500 kg of urea increased the yield of green leaves by 14.8% compared to unshaded conditions, while the lowest yield was recorded in Treatment 1. Application of 50% shade had a significant positive effect on green leaf yield relative to unshaded conditions, whereas 90% shade did not produce a positive yield response. The use of 50% shading increased the number of harvestable shoots by 35.3% compared to unshaded plants, with the lowest shoot number observed in unshaded bushes receiving 250 kg of urea. The treatments also had a significant effect on nitrogen concentration in green tea leaves. The highest nitrogen concentration was in Treatment 4, which differed significantly from unshaded treatments and from 90% shade with 500 kg of urea. The lowest nitrogen concentration was found under 90% shade with 500 kg of urea, which did not differ significantly from the unshaded treatments. The highest chlorophyll content and water extract values (37%, 0.68) were observed in Treatment 6, representing increases of 37.2% and 29.27%, respectively, compared to the unshaded treatment with the same fertilizer level. Overall, the results indicate that 50% shading combined with urea has a more positive effect on green leaf yield, whereas 90% shading with urea application exerts a greater influence on quality characteristics, particularly leaf chlorophyll content.
Conclusion: The results demonstrated that the quantitative and qualitative characteristics of green tea leaves are strongly influenced by changes in light availability. Given the simplicity and practicality of installing greenhouse shade nets compared to establishing different canopy trees in existing tea gardens, and based on the findings of this study, it can be concluded that 50% shade combined with nitrogen fertilizer exerts a more favorable impact on green leaf yield. However, 90% shade and nitrogen fertilizer have a superior effect on the quality attributes of green leaves, especially chlorophyll content. Therefore, considering the intended purpose of tea production, it can be suggested that 50% and 90% shade nets are more suitable for producing black tea and green tea, respectively.

Keywords

• Tea
• shading
• yield
• chlorophyll
• water extract

Main Subjects

• Agriculture and horticulture