推荐回答(3个)
苜蓿栽培悠久而广泛。在从西班牙到中国,从瑞典到北非的广大地区都有野生苜蓿分布。现在的非洲南部、欧洲、大洋洲、北美洲、南美洲都有大面积栽培的苜蓿。
苜蓿主要分布于温暖地区,在北半球大致成带状分布,美国、加拿大、意大利、法国、中国和苏联南部是主产区;在南半球只有某些国家和区域有较大规模的栽培。阿根廷、智利、南非、澳大利亚、新西兰栽培较多。
对苜蓿栽培面积,目前尚无权威的精确统计数据,其生产总体上是在发展扩大,但是20世纪80年代全世界种植面积比60年代末稍有减少,主要原因是70年代中叶,能源危机影响了苜蓿脱水工业,再加上病虫害盛行,致使苜蓿产业遭受到很大打击,欧洲许多国家的苜蓿种植面积都明显减缩,而代之以更能赚钱的其他作物。由于科学技术的发展,在苜蓿的新品种选育、病虫草害的控制、综合开发利用等方面都取得了长足的进步,到90年代全球苜蓿生产又略有回升。

苜蓿是苜蓿属(Medicago)植物的通称,俗称"三叶草"(三叶草亦可称其他车轴草族植物),多年生开花植物,其中最著名的是作为牧草的紫花苜蓿(Medicago sativa),是牲畜饲料。
一年生或多年生草本植物;羽状3小叶,小叶小,有小齿,叶脉伸入齿端;托叶与叶柄合生;花小,组成腋生的短总状花序或头状花序;萼齿近相等;花冠黄色或紫,旗瓣倒卵形或长圆形,基部渐狭,近无柄,龙骨瓣钝,比翼瓣短;雄蕊10,二体(9+1);子房有胚珠多数,花柱短,扁或锥状;荚果旋卷,常呈贝壳状或弯镰状,不开裂,平滑或有刺,有种子1至数颗。可作为食物,将其在热水中焯过,凉拌即可,味道极佳。
本属多系重要的饲料植物,世界各地广泛引种栽培。
Medicago L. 苜蓿属,蝶形花科,65种,分布于欧洲、亚洲和非洲,我国有16种,分布颇广,野生和栽培均有,为良好的饲料。一年生或多年生草本;羽状3小叶,小叶小,有小齿,叶脉伸入齿端;托叶与叶柄合生;花小,组成腋生的短总状花序或头状花序;萼齿近相等;花冠黄色或紫,旗瓣倒卵形或长圆形,基部渐狭,近无柄,龙骨瓣钝,比翼瓣短;雄蕊10,二体(9+1);子房有胚珠多数,花柱短,扁或锥状;荚果旋卷,常呈贝壳状或弯镰状,不开裂,平滑或有刺,有种子1至数颗。
中国江浙沪地区称黄花苜蓿为草头,又名金花菜,称紫花苜蓿为草紫,有时亦将两种苜蓿均称为草紫。每百克鲜菜含维生素C:118毫克;钙:713毫克;铁:9.7毫克;硒:8.5毫克。苜蓿可碱化体质并为身体解毒,用作利尿剂,可抗发炎及抗霉菌。降低胆固醇、平衡血糖及荷尔蒙、促进脑下垂体功能。对贫血、关节炎、溃疡、出血性疾病、骨骼或关节疾病、消化系统和皮肤均有帮助。

苜蓿属豆科苜蓿属多年生草本,喜温暖、半潮润到半干旱气候条件,耐盐碱、耐旱、不耐水淹,再生能力强。常见的有紫花苜蓿和黄花苜蓿两类,以前者分布最广,主要分布在西北、华北和东北地区,是我国目前栽培最多的牧草。可以单播,也可以与禾本科牧草,如羊草、苏丹草、无芒雀麦混播。品质好,产量高,被称为“牧草之王”。其蛋白质含量高,每公顷苜蓿含粗蛋白1500-3000kg,相当于18.75-37.5℃玉米所含蛋白,必需氨基酸齐全,干物质中赖氨酸含量是玉米的5倍;富含维生素和矿物质,其中钼0.2mg/kg,钴0.2mg/kg,胡萝卜素18-161mg/kg,维生素C5-6mg/kg,B族维生素5-6mg/kg,维生素K150-200mg/kS0,苜蓿适口性好,消化率很高,有机物消化率一般可达60-80%,粗纤维可达40%以上。不论鲜喂还是制成干草,都是家兔的优质饲料。

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