Abstract: To explore the response mechanism of alfalfa productivity,quality formation,and sustainability to cutting height,a finely controlled pot experiment was conducted to study the effects of four cutting heights (H30,30 cm;H40,40 cm;H50,50 cm,and H60,60 cm) on aboveground and below biomass,nutritional quality and root characteristics of alfalfa. The results showed that the aboveground biomass of alfalfa,regrowth rate,below biomass,specific root length,and taproot diameter of alfalfa increased significantly with the increase of cutting height,but the relative feed value decreased significantly. Taproot diameter was positively correlated with below biomass and regrowth rate (P<0.05). There was a binomial curve relationship between cutting height and crude protein yield (P<0.05),and a significant positive linear correlation between cutting height and change rate of taproot diameter (P<0.05). According to the linear analysis of taproot diameter change rate and cutting height,when the cutting height was lower than 45.13 cm,the taproot became thinner,and the growth of the aboveground part would consume the nutrient stored in the root system,thus reducing the persistence and limiting the production potential of alfalfa. The results can provide data support for the scientific utilization of alfalfa grassland.

Key words: Cutting height, Aboveground biomass, Regrowth rate, Relative feed value, Root characteristics

摘要： 为探究紫花苜蓿（Medicago sativa L.）生产力，品质形成和可持续利用性能对刈割高度的响应机制，本研究采用盆栽精细控制试验，探究了4个刈割高度处理（H30，30 cm；H40，40 cm；H50，50 cm和H60，60 cm）对紫花苜蓿地上地下生物量、营养品质和根系形态特征的影响。结果表明：随着刈割高度的增加，紫花苜蓿地上地下生物量，再生速度，比根长与主根直径均显著增加，相对饲喂价值显著降低；主根直径与地下生物量和再生速度均呈显著正相关关系（P<0.05）；刈割高度与粗蛋白产量和主根直径变化率呈显著正相关关系（P<0.05）；刈割高度低于45.13 cm时，降低紫花苜蓿草地的持久性，限制生产潜力的发挥。研究结果可为紫花苜蓿草地科学利用提供数据支撑。

关键词: 刈割高度, 地上生物量, 再生速度, 相对饲喂价值, 根系特征