Investigating the Interaction of Irrigation Regimes and Pressure Irrigation Methods on yield and water use efficiency of tea plant in Fooman region

Tea is the most popular drink after water in the world and more and more people are consuming it every day. Therefore, it is necessary to increase the production of this product per unit area. Since in some months of the year the amount of rainfall does not meet the water requirement of the plant, to produce more product per unit area, Supply of water shortage with proper irrigation method is unavoidable.

In order to investigate the effect of different irrigation methods and irrigation levels on the yield and water use efficiency of Chinese hybrid cultivar tea plant (Camellia sinensis L.), an experiment was conducted as split plots based on randomized complete blocks design in three replications with three main treatments including permanent sprinkler irrigation (SI), local drip irrigation (DI) and strip drip irrigation (TDI), and three sub-treatments including without irrigation (I0), 50 (I1) and 100 (I2)% of crop water requirement in 1399 in the Research Station of Fashalam tea garden in Fooman region. In order to determine the physical and chemical properties of the soil in the study area, soil samples were taken from a depth of 0 to 20, 20 to 40 and 40 to 60 cm and were analyzed in the laboratory. In this experiment, the field capacity, permanent wilting point, bulk density and pH was determined and soil texture was measured by hydrometric method. The meteorological data required to calculate the water requirement of the tea plant were prepared from the Rasht agricultural meteorological station. The amount of rainfall during the irrigation period (May to November) in 2020 was equal to 307.197 mm, which was lower than the average rainfall of the last 30 years in the same irrigation period was 188.2 mm. The water requirement of the tea plant was calculated using the daily data of 30 years of Rasht agricultural meteorological station with penman monteith FAO method by software of CROPWAT 8.0, and then the daily water requirement of the plant by considering the water use efficiency of 80% in sprinkler irrigation system and 95% in the drip irrigation system was determined. Gross amount of irrigation water was determined based on plant water requirement, soil moisture holding capacity and water use efficiency in sprinkler and drip irrigation systems. The net amount of irrigation water in the treatment of the 50% of the plant water requirement was equal to 50% of the amount of the net irrigation water in the treatment 100% of the plant water requirement. The volume of water given to each plot at each irrigation period was measured using a water meter to the nearest tenth of a liter.

The results of the data variance analysis showed that the effect of irrigation methods, different levels of irrigation and their interaction on the yield of green and dry tea leaves and water use efficiency based on green and dry tea leaves were significant at the level of one percent probability. So that the average of the lowest green and dry leaf yield and water use efficiency based on green and dry leaves with 3846.90 and 1044/7 kg/ha, and with 1.23 and 1.33 kg/m3 in DI irrigation method and the highest of them with 7859.70 and 2129.6 kg/ha, and with 2.39 and 0.65 kg/m3 were observed in SI irrigation method which increased by 2.043 and 2.038, and 1.94 and 1.97 times in compared with DI irrigation method, respectively. Also, the lowest green and dry leaf yield and water use efficiency based on green and dry leaves with 1050.1 and 299.16 kg/ha, and 0.44 and 0.13 kg/m3 at I0 irrigation level, and the highest of them with 8947.20 and 2418.17 kg/ha, and 2.53 and 0.65 kg/m3 were observed at I2 irrigation level which increased by 8.52 and 8.08, and 5.75 and 5.00 times in compared with I0 irrigation level, respectively. The results of the interaction of irrigation methods at different levels of plant water requirement on green tea leaf yield showed that the highest yield with 13000 kg/ha was obtained in SI irrigation method with I2 irrigation level. Therefore, SI irrigation method with I2 irrigation level can be considered as optimum method to the tea green leaf production in the Fooman region.