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茶树是采叶作物,在它生长发育过程中对氮素的要求十分迫切,因此各产茶国在茶叶生产中都十分重视氮肥的施用。据苏联研究,在茶树栽培中施氮肥最有增产效果,比不施可增产5—8倍。受益率也最高、在每公顷施纯氮300公斤的条件下受益率高达300—350％。日本是世界上茶园施肥水平最高的国家,所推荐的氮肥用量,每公顷为600公斤氮,但每公顷施1200公斤也屡见不鲜,还有所谓高肥栽培法的茶园,每公顷要施2000—2500公斤的氮,印度,斯里兰卡,以及中、东非诸产茶国,每年每公顷茶园也要施200—400公斤的氮,并有日益提高的趋势。由于氮肥用量不断提高,利用率和经济效果不断下降,茶园土壤不断酸化,理化性质恶化,茶区环境污染加剧。因此,世界各主要产茶国对茶园的氮素平衡,茶树对氮素的吸收,肥料氮在土壤中的转化等问题都十分关注。工业较发达的产茶国,如日本、苏联等用同位素~N(15)进行了多方面的研究。他们采用水培、砂培、土培试验
Tea tree is a leaf-harvesting crop, and its requirement for nitrogen in its growth and development is very urgent. Therefore, all tea-producing countries attach great importance to the application of nitrogen fertilizer in tea production. According to the study of the Soviet Union, the most yield-increasing effect of nitrogen fertilizer in tea tree cultivation is 5-8 times higher than that of no fertilizer application. The highest rate of benefit, the rate of benefit of up to 300-350% per hectare under the condition of 300 kg of pure nitrogen. Japan is the country with the highest level of fertilization in the tea plantations. The recommended amount of nitrogen fertilizer per hectare is 600 kilograms of nitrogen, but it is not uncommon for 1,200 kilograms per hectare. There is also a so-called high-fertility cultivation of tea plantations with 2000-2500 hectares Kilograms of nitrogen, India, Sri Lanka, as well as the Middle East and East African tea producing countries, also apply 200-400 kilograms of nitrogen per hectare of tea plantations per year and are on the rise. Due to the increasing use of nitrogen fertilizer, the utilization rate and economic effect are declining, the soil of the tea plant is continuously acidified, the physical and chemical properties are deteriorated, and the environmental pollution in the tea area is aggravated. Therefore, all the major tea producing countries in the world pay close attention to such issues as the balance of nitrogen in tea plantations, the absorption of nitrogen by tea plants and the conversion of fertilizer nitrogen in the soil. The more advanced industrialized tea-producing countries, such as Japan and the Soviet Union, carried out various studies using isotope ~ N (15). They use hydroponics, sand culture, soil culture test