| To study the effects of different supplemental irrigation systems on the growth, yield, and water use efficiency of broomcorn millet under limited irrigation conditions during the critical growth period and to explore the optimal supplemental irrigation system to achieve the goal of efficient water use and stable and high yield. In 2022 and 2023, 'Yumi No. 2' was taken as the research object, and the field experiment was conducted in Yulin, Shaanxi Province. In the experiment, 50% of the field water capacity of the 0~20 cm soil layer was taken as the lower irrigation limit, and 70% and 90% of the field water capacity of the 0~20 cm soil layer were designed as the upper irrigation limit, respectively. Two supplemental irrigation periods were set up: supplemental irrigation at the heading stage and supplemental irrigation at the jointing stage + heading stage. Specifically: supplementary irrigation at heading to 70% θf (H70), supplementary irrigation at heading to 90% θf (H90), supplementary irrigation at the jointing to 70% θf + supplementary irrigation at the heading to 70% θf (J70H70), supplementary irrigation at the jointing to 70% θf + supplementary irrigation at the heading to 90% θf (J70F90), supplemental irrigation at the jointing stage to 90% θf + supplemental irrigation at the heading stage to 70% θf (J90H70), and supplemental irrigation at the jointing stage to 90% θf + supplemental irrigation at the heading stage to 90% θf (J90H90). Non-mulched rainfed (CK) was used as a control. The effects of different supplemental irrigation periods and amounts on plant height, leaf area index (LAI), dry matter accumulation and translocation, yield, and water use efficiency of broomcorn millet were studied. Supplemental irrigation significantly promoted the growth and development of broomcorn millet, increased the dry matter accumulation rate, number of ears, number of grains per ear, water use efficiency, and precipitation use efficiency, and shortened the rapid growth period（ΔT）. With the increase of supplemental irrigation amount, irrigation water use efficiency and irrigation benefit gradually decreased. This study showed that the yield and water use efficiency of H90 were 3790.41~4748.99 kg/hm2 and 1.45~1.85 kg/m3. The yield and water use efficiency of J90H70 were the highest (4067.39~5373.72 kg/hm2, 1.59~1.96 kg/m3), which were 54.41%~88.73% and 31.20%~55.25% higher than those of CK, respectively. Under the condition of limited irrigation, considering the yield, water use efficiency, and irrigation benefit, J90H70 is the optimal supplementary irrigation scheme for high yield and high efficiency. When the water was supplemented once, the H90 irrigation strategy could achieve the yield increase effect of J70H70 and save the production cost. This study can provide a theoretical basis for promoting the efficient production of water-saving agriculture in broomcorn millet in arid and semi-arid areas. |