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微量营养元素通常富集在表层土壤中,其含量随土层深度递减。尽管土壤中大多数微量元素的含量很高,但只有一小部分能被植物吸收。微量营养元素,也被称为痕迹元素,所需数量微小,但其缺乏会对农作物生产和动物健康造成严重影响。农作物对不同微量营养元素有着不同的反应。芸苔和豆类对Mo和B有较高的响应度,而玉米和其他谷类对Zn和Cu较为敏感。在温润和湿热地区,由于强降雨和强淋溶作用,微量营养元素缺乏较为普遍。土壤pH值是影响微量营养元素对植物有效性的重要因素之一。除Mo以外,微量营养元素的有效性随pH的增加而减小,Mo的有效性随pH的增加而增加。对于大多数植物来说,叶片中的微量营养元素含量高于植物的其他部分。因此,可以用叶片作为样品来测定农作物中微量营养元素的含量。大多数微量营养元素缺乏表现在植物顶部的新叶上,而过量则表现在老叶上。根据Deckers和Steinnes的结论,土壤较为贫瘠的发展中国家与土壤肥沃的欧洲及北美地区相比,微量营养元素缺乏现象较为普遍。许多营养元素缺乏区位于潮湿的热带地区,土壤极度贫瘠、高度风化和/或强淋溶,营养元素十分匮乏。此类其他土壤分部于半干旱及毗邻地区,这些地区的碱性和石灰性土壤条件严重限制了微量营养素对植物的供给。通常,可以满足草料作物生长的Cu、Fe、Mn、Zn、Se含量水平,却不能满足家畜的需要。Se是植物生长所不需要的微量元素,因此草料作物中Se的含量很少。然而,如果动物所食农作物和草料中Se含量偏低,会造成严重的肌肉异常和其他疾病。白肌病是最常见的由于Se缺乏造成的疾病,在牛犊和羔羊中都有发现。本文讨论了与动物需求相关的农作物微量营养元素充足度。
Micronutrients are usually enriched in topsoil and their content decreases with soil depth. Although most trace elements in soils are high, only a small fraction of them can be absorbed by plants. Micronutrients, also known as trace elements, require small quantities, but their lack may have a serious impact on crop production and animal health. Crops have different responses to different micronutrients. Brassica and beans have a higher responsiveness to Mo and B, while maize and other grains are more sensitive to Zn and Cu. In warm and humid areas, micronutrient deficiencies are more common due to heavy rains and strong leaching. Soil pH is one of the important factors that affect the availability of micronutrients to plants. In addition to Mo, the availability of trace nutrients decreases with increasing pH, and the effectiveness of Mo increases with increasing pH. For most plants, the micronutrients in the leaves are higher than the rest of the plant. Therefore, the leaves can be used as samples to determine the content of micronutrients in crops. Most micronutrient deficiencies are found on the new leaves on the top of the plant, whereas over-abundance is on the old leaves. According to Deckers and Steinnes, micronutrient deficiencies are more common in developing countries with poor soils compared to fertile Europe and North America. Many areas lacking nutrients are located in humid tropical areas, where the soil is extremely poor, highly weathered and / or strongly leached, and nutrients are scarce. Such other soils are subdivided into semi-arid and adjacent areas where alkaline and calcareous soil conditions severely limit the supply of micronutrients to plants. Generally, the content of Cu, Fe, Mn, Zn and Se in forage crops can be satisfied, but they can not meet the needs of livestock. Se is a trace element that is not needed for plant growth, so Se content is low in forage crops. However, low levels of Se in animals and forages can cause severe muscle abnormalities and other diseases. White muscle disease is the most common disease caused by lack of Se, found in calves and lambs. This article discusses the micronutrient abundance of crops associated with animal needs.