Effects of different irrigation rates on the yield and quality of greenhouse-cultivated Platycodon grandiflorus crops considering transpiration

The consumption of agricultural water resources is enormous, and in the face of water scarcity, optimizing the utilization rate of water resources is an urgent need. As a common medicinal plant, the planting area of Platycodon grandiflorus crops has increased. Therefore, in order to maximize the yield and quality of Platycodon crops, different irrigation treatment methods are developed in this study based on their evaporation capacity and the impact of different irrigation amounts on Platycodon crops is explored. Different irrigation amounts affect various indicators of Platycodon plants. The experimental results of this study indicate that for the daily transpiration of Platycodon, 120% irrigation is more effective during the maturity period, and the stemflow efficiency performs better overall on sunny days. Irrigation at a rate of 120% can obtain the maximum number of leaves. Regarding the quality of Platycodon grandiflorus crops, 120% irrigation can achieve the highest contents of saponins, flavonoids, and polysaccharides, but 100% irrigation is required to achieve the highest soluble protein contents. Overall, Platycodon crops require 100% irrigation during the flowering stage and 120% irrigation during the maturity stage. As the temperature increases, the irrigation amount should be appropriately increased, and it should be reduced as the temperature decreases. This research demonstrates the impact of irrigation volume on Platycodon crops, and controlling the irrigation volume can effectively enhance the utilization efficiency of water resources.