中文摘要：

对4个苜蓿品种进行不同频次的刈割处理，结果表明，在我国北方地区，黄花苜蓿和杂花苜蓿每年适合刈割2次，此时，地上生物量和粗蛋白质产量均达到最大值；而紫花苜蓿刈割2或3次均可，地上生物量和粗蛋白质产量在刈割2和3次之间差别不大，但明显高于刈割1和4次处理；不同苜蓿品种的粗蛋白质含量与形态发育阶段之间均呈极显著的二次相关，均表现为先下降后上升的趋势。此外，通常认为的黄花苜蓿比紫花苜蓿粗蛋白质含量高，并非是由物种的差异引起的，而主要是由收获时生育阶段的差异引起的。

英文摘要：

Four alfalfa eultivars were mowed with different frequencies. Medicago falcata and M. varia should be mowed two times in the whole growing season in North China, while M. sativa should be mowed two or three times for maximum yield. There was no significant difference in yields of biomass and crude protein when M. sativa was mowed two or three times, although they were higher than for plants mowed one and four times. The correlation in development and crude protein content was an extremely significant quadratic regression. It was the diversity of the morphological development stage that caused the difference of crude protein content in the four alfalfa eultivars.