Abstract: In order to explore whether the porous character of biochar could promote the growth of Medicago sativa L. by improving the nitrogen-fixing ability of rhizobia,we studied the effects of different levels of biochar addition and drought stress on photosynthetic efficiency and growth of Medicago sativa L,which inoculated with rhizobia ‘sm1021’. The experiment had four water treatments and five biochar level (0%,0.5%,1%,1.5%,2%). The result showed that the drought stress depressed both growth and photosynthesis (Pn) of the plant significantly,moreover,the severe drought inhibited plant growth and photosynthesis (Pn); Biochar additions promoted the Pn and alfafa growth; As the biochar level increased,the photosynthetic efficiency and biomass of alfafa increased initially and then decreased. Overall,the result showed that addition of biochar at the level of 0.5%~1% could increasd leaf area and Pn,alleviate the damage caused by drought stress and promote alfafa growth.

Key words: Biochar, Drought stress, Alfalfa, Photosynthetic efficiency, Rhizobium

摘要： 试验以接种根瘤菌‘Sm1021’的紫花苜蓿（Medicago sativa L.）为材料，将土壤和生物炭按比例混合（0%，0.5%，1%，1.5%，2%），然后进行不同程度（正常土壤水分处理，轻度，中度，重度）干旱胁迫，旨在研究土壤中添加不同水平生物炭与干旱胁迫对接种根瘤菌紫花苜蓿光合效率及生长的影响，探讨生物炭多孔性特性是否能够提高根瘤菌固氮能力，从而促进苜蓿生长。结果表明：干旱胁迫显著抑制紫花苜蓿的光合效率和生长（P<0.05），重度干旱抑制作用最显著（P<0.05）；添加生物炭能够提高接种紫花苜蓿光合效率，促进植株生长；随生物炭水平升高，紫花苜蓿光合效率和生物量先增加后降低。研究认为，添加0.5%~1%水平的生物炭可增加接种紫花苜蓿叶面积，促进光合效率，缓解干旱胁迫对植株造成的伤害，从而促进生长。

关键词: 生物炭, 干旱胁迫, 紫花苜蓿, 光合效率, 根瘤菌