Annual change of potassium content and accumulation in apple tree

Chinese. 以“富士”苹果树为试材，对树体生物量及不同器官钾含量和钾累积量的变化规律进行了研究。结果表明，03-26～09-21，果树地上部和整株的生物量逐渐增加，果实成熟期（09-21）之后趋于平稳；03-26～07-30，根系生物量几乎没有变化，07-30以后快速增加。果树新生器官（果实、叶片和新梢）中钾含量均表现为物候期前期较高，中后期较低；成龄器官（枝、干、根系）中钾含量基本呈降低的趋势，但变化幅度较小。03-26～04-30，果树主要利用贮藏的钾素建造器官；04-30～09-21，果树生长所需的钾素主要依靠根系从土壤中吸收，且钾素分配随生长中心的变化而转移。03-26～07-30，整株钾累积量逐渐增加，于07-30达最大，之后降低；年周期内根系钾累积量变化较小。不同时期各器官中钾累积量差异较大。07-30～09-21，果实中钾累积量增加幅度最大，建议果实膨大前适当增施钾肥以提高苹果产量。

English. With “Fuji” apple trees used as the subject, biomass, potassium content and accumulation in different parts of apple trees were studied in this paper. The results showed that biomass of the parts above ground and tree increased slowly from Mar. 26 to Sep. 21, and kept placid after fruit harvest time (Sep. 21). But biomass of roots system had no change from Mar. 26 to Jul. 30, and increased quickly after Jul. 30. Potassium content in new organs (fruits, leaves and shoots) during early spring was higher than that at other time. The curve of potassium content in old organs (branch, trunk and root) fell. From Mar 26 to Apr. 30, trees mainly constructed organs by using storage potassium; the necessary potassium nutrition for tree growth was absorbed by roots from soil from Apr. 30 to Sep. 21, and potassium distribution changed with the growth center. From Mar. 26 to Jul. 30, potassium accumulation of tree increased gradually, and reached the highest in Jul. 30, then decreased. Potassium accumulation in roots system almost had no change in one year. Potassium accumulation in different organs of apple trees changed largely at different time. From Jul. 30 to Sep. 21, potassium accumulation in fruits increased quickly, so it was better to fertilize for improving output before fruit expansion time.