Determination of Optimal Drip Irrigation Timing and Duration for Tea Field in Yangtze River Region of China

Drought frequently constrains tea production in low-slope hilly regions, where inefficient irrigation scheduling often leads to substantial water losses. This study optimized drip irrigation management for tea plantations by quantifying soil wetting dynamics under different emitter flow rates, spacings, and initial soil water content conditions. Field and laboratory experiments were conducted to investigate wetting-front migration, wetted-body morphology, and soil moisture redistribution. The results showed that emitter flow rate primarily controlled the migration of vertical and lateral wetting fronts, whereas emitter spacing mainly influenced the overlap degree and uniformity of the soil wetted body (SWB). Both vertical and lateral wetting fronts exhibited strong power-function relationships with irrigation duration (R2 > 0.98). The optimal configuration for achieving an effective root-zone wetting depth of 40–45 cm was identified as a flow rate of 2.0 L·h−1 combined with a spacing of 40 cm. Based on multi-depth soil moisture monitoring, a soil water content equivalence model was developed to determine irrigation initiation and duration. Validation experiments demonstrated that the proposed control strategy reduced irrigation water use by 17.6% compared with the conventional method while maintaining adequate root-zone moisture distribution. These findings provide a practical framework for precision irrigation management in tea plantations under drought-prone hilly conditions.