土壤碳氮比对平邑甜茶幼苗生长和碳氮分配的影响

为探讨土壤碳氮比(C:N)对苹果(Malus pumila)植株生长和碳氮分配特性的影响, 采用碳氮双标记示踪技术, 以二年生平邑甜茶(Malus hupehensis)幼苗为试验材料, 研究了6个不同土壤C:N处理(T1-T6分别为4.70、9.78、14.70、19.96、25.60和28.83)下平邑甜茶的生长状况和氮素吸收、利用分配以及碳水化合物的运转特性。结果表明, 随着土壤C:N的逐渐增大, 平邑甜茶幼苗根系干重逐渐增加, 而株高、茎粗、地上部干重和植株总干重呈先增加后降低的趋势, 以T4处理最大。土壤C:N显著影响了平邑甜茶幼苗的 ¹⁵N利用率, 从T1到T4处理, 植株的 ¹⁵N利用率逐渐升高, T4处理(18.46%)是T1处理(10.65%)的1.73倍; 随着土壤C:N的进一步增加, 植株的 ¹⁵N利用率逐渐降低, T5和T6处理分别比T4处理降低了1.59%和2.58%。土壤C:N较低的T1和T2处理, 平邑甜茶幼苗各器官从肥料中吸收分配到的 ¹⁵N量对该器官全氮量的贡献率(Ndff)大小顺序为根>叶>茎, 随着土壤C:N的进一步增大, 叶片的Ndff均为最大, 其次是根, 茎最少。随着土壤C:N的增大, 叶片 ¹⁵N分配率逐渐升高, ¹³C分配率逐渐降低; 而根系 ¹⁵N分配率逐渐降低, ¹³C分配率逐渐升高。综合考虑植株生长和氮素利用状况, 本试验条件下适宜平邑甜茶生长的土壤C:N为21-23。

Effects of soil C:N on growth and distribution of nitrogen and carbon of Malus hupehensis seedlings

Aims Soil C:N is a sensitive indicator of soil quality and an indicator for assessing carbon and nitrogen nutrition balance of soils. Our objective was to explore the effects of soil C:N on growth and distribution of nitrogen and carbon of Malus hupehensis seedlings.
Methods Using the track technology of C and N double mark, we investigated growth parameters (height, stem diameter and dry matter of different organs), ¹⁵N parameters (absorption, N derived from fertilizer, distribution and utilization) and ¹³C parameters (distribution in different organs) of two-year old M. hupehensis seedlings under six different soil C:N treatments (T1-T6 were 4.70, 9.78, 14.70, 19.96, 25.60 and 28.83, respectively).
Important findings With increase of soil C:N, dry matter of roots increased significantly, while the height, stem diameter and dry matter of above ground parts and total plant increased at first and then decreased. The highest value appeared in the T4 treatment. There were significant differences in ¹⁵N utilization efficiency among the six different treatments. ¹⁵N utilization efficiency increased from T1 to T4, and the rate of T4 (18.46%) was 1.73 times than that of T1. But, the ¹⁵N utilization efficiency decreased with a further increase of soil C:N, as the rate of T5 and T6 reduced that of T4 by 1.59% and 2.58%, respectively. In the two lower soil C:N treatments (T1 and T2), the order of Ndff value ( ¹⁵N derived from fertilizer) in the organs was roots > leaves > stems. With increase of soil C:N, Ndff value in leaves was the highest, followed by roots and stems. ¹⁵N distribution ratio in leaves increased, while ¹³C distribution decreased with increase of soil C:N, but the changes were the opposite in roots. Considering plant growth and utilization of nitrogen, the suitable soil C:N was 21-23 under these experimental conditions.