Abstract: Alfalfa has the largest plant area among forage legumes in China, but the quality and yield of the forage are often affected by improper harvesting technology in a conventional harvesting system. To study the effect of different stubble heights and drying times on the hay quality of alfalfa, the yield, stem/leaf ratio, overwintering rate, water evaporation rule and nutrition value of alfalfa were analyzed when the 0, 2~5, 5~8 and 8~11 cm stubble heights of the forage plants are kept, respectively. Results showed that the treatment of 2~5 cm stubble height had significantly higher grass yields than other stubble height treatments at all tested seasons (P<0.05). And it also had higher production capacities, crude protein (CP) contents and relative feeding values (RFV). The stubble height of last cutting should be 8~11 cm because the regrowth rate of following year was 77.44% with the stubble height and significantly higher than other stubble heights (P<0.05). The leaf abscission rate was 56% after 72 hours drying, while the leaf loss rate was only 29% when the moisture content decreased to 52%. These results indicated that leaf drying had an asynchrony with stem drying in the late period.

Key words: Alfalfa, Stubble height, Stem/leaf ratio, Greening rate

摘要： 紫花苜蓿（Medicago sativa L.）是我国种植面积最大的豆科牧草，但在常规的收获制度中因收获技术不当往往造成其品质下降和产量降低。为研究不同刈割留茬高度和不同晾晒时间对苜蓿干草品质的影响，将苜蓿草按留茬高度为0，2~5，5~8，8~11 cm进行刈割，并对其草产量、茎叶比、越冬率、水分散失规律及营养价值进行测定分析。结果表明：刈割留茬高度为2~5 cm时不仅能获得高产的苜蓿草，且其后2茬的草产量也显著高于其他留茬高度的（P<0.05），具有较高的持续生产能力；同时其粗蛋白（CP）含量和相对饲喂价值（RFV）较高。末茬苜蓿草的刈割留茬高度应在8~11 cm，此条件下其翌年的返青率（77.44%）显著高于其他留茬高度下的（P<0.05）。苜蓿经72 h晾晒至安全含水量时，叶片脱落率达56%，而在含水量降至52%时叶片损失率仅为29%，即后期出现严重茎叶干燥不同步现象。基于此，建议苜蓿干燥过程中采用茎秆压扁技术。

关键词: 紫花苜蓿, 留茬高度, 茎叶比, 返青率