To prevent Drought damage in Tea gardens and reduce losses in tea production, supplementary measures to replenish water and suppress evaporation can be taken before the onset of drought. These include irrigation to supplement water, loosening the soil and weeding, inter-row grass covering, etc., to maintain and regulate Soil moisture and improve the microclimate around the tea plants, thereby enhancing the tea trees' drought resistance.
Irrigation Replenishment
Tea garden irrigation methods include furrow irrigation, sprinkler irrigation, drip irrigation, among others, each with its own advantages and disadvantages. Furrow irrigation is suitable for flat tea gardens and can quickly increase soil moisture levels, promptly rescuing drought-stressed tea trees, but it consumes a large amount of water, has a small impact on air humidity, and can lead to waste of water resources through surface runoff and deep seepage, as well as damaging some of the topsoil structure. Drip irrigation reduces evaporation and saves water, but it requires a higher initial investment and cannot effectively improve the microclimate of the tea garden. Therefore, in recent decades, sprinkler irrigation has been the primary method used for drought prevention and mitigation in tea gardens.
Sprinkler Irrigation can not only increase soil moisture but also lower the air temperature and Leaf surface temperature near the tea bushes, increase relative humidity in the air, and improve the microclimate of the tea garden, achieving comprehensive drought resistance. Experimental data shows that during high-temperature drought periods in Hangzhou, 24 hours after sprinkler irrigation, the ground surface temperature in the irrigated area is 2.0-4.8°C lower than in the control area, with the highest temperature reduction reaching 9°C. When the humidity at a depth of 10 cm drops below 60% of field capacity or when the daily maximum temperature exceeds 35°C or the average daily temperature is greater than 30°C during the transition between summer and autumn, the tea garden can be thoroughly irrigated every 4-5 days to meet the soil moisture needs of the tea trees. At other times, the garden should be sprayed at least once a day to enhance the microclimate effects above ground.
For promoting tea bud growth, it is best to spray twice a day, in the morning and afternoon. During hot summer nights, tea buds grow by 80% of their total daily elongation, and spraying water in the afternoon is appropriate for supplying the necessary moisture for nighttime growth. Observational data indicates that immediately after sprinkler irrigation, the temperature drops by 4.0-5.0°C, and the increase in relative humidity can reach 30%. The average daily cooling effect is 1.0-2.0°C, and the daily increase in humidity is 5%-10%. According to gradient calculations, the cooling and humidifying effects of sprinkler irrigation are not significant above 200 cm from the ground surface, and the cooling effect diminishes over time after irrigation.
Water Retention and Moisture Conservation
Before the occurrence of drought and heat stress, measures such as intermediate cultivation and soil loosening, combined with fertilization and covering the ground between tea rows with straw, can reduce surface runoff, prevent soil erosion, allow more water to slowly infiltrate deeper into the soil, and reduce the intensity of soil surface evaporation. This helps conserve water and moisture, reducing the harm caused by drought to tea trees.
Shade for Drought Resistance
For young tea gardens, intercropping with short-stemmed green manures (such as Sesbania and Stylosanthes) or placing branches of evergreen trees like Chinese fir or camphor next to tea seedlings can provide shade for young tea plants to resist drought.
This article refers to “Tea and Meteorology,” edited by Li Zhuo and He Lingxuan, published by China Meteorological Press.