Regulated deficit irrigation induces compensatory growth in Tibetan barley by optimizing growth dynamics

Regulated deficit irrigation (RDI) is a key strategy for efficient irrigation water management in barley production on the Qinghai-Tibet Plateau. However, the responses of barley water consumption patterns and biomass dynamics to RDI remain unclear. Field experiments in 2023 and 2024 tested five irrigation regimes: no deficit (ND), moderate deficit at vegetative stage (MV), severe deficit at vegetative stage (SV), moderate deficit at reproductive stage (MR), and severe deficit at reproductive stage (SR). Results showed that severe water deficit treatment led to a significant 8.90–20.12% reduction in crop evapotranspiration when compared with ND. The highest yield was observed under ND (5115.97 and 5317.22 kg ha–1 in 2023 and 2024, respectively), which showed a significant difference with SV. However, RDI had no significant effect on water productivity. Moreover, water deficit during the vegetative stage delayed early growth, increasing the accumulated thermal time required for growth initiation by 21.31–56.19% compared with other treatments across years. Yield showed a significant positive correlation with duration of the rapid growth period, maximum growth rate, and mean growth rate. Taken together, Tibetan barley exhibits compensatory growth after rewatering by regulating its growth rate. This study highlights barley’s drought tolerance at key growth phases and quantifies compensatory effect based on the temperature-dependent growth process.