Impact of Harvest Time on the Dry Matter Content, and Nutritional Parameters Related to Forage Quality of Maralfalfa (Cenchrus purpureus (Schumach.) Morrone, Poaceae) under Mediterranean Climate

地中海气候下收获时间对紫花苜蓿（Cenchrus purpureus (Schumach.) Morrone, Poaceae）干物质含量及与牧草品质相关的营养参数的影响