地表覆盖对陇东旱塬苹果根系生长与越冬前后树体贮藏营养的影响

Effects of mulching on root growth and nutrient reservation in overwintering apple trees grown in the dry area of eastern Gansu

【目的】探明陇东旱塬区不同覆盖措施（覆膜、覆草）对苹果园根系生长分布及树体不同器官中贮藏营养分配动态的影响。【方法】以14 a生苹果树为试材,采用土壤剖面分层取样法,对不同径级根系进行空间形态分布调查,测定根系、不同枝类越冬期间贮藏营养的分配比例及动态。【结果】覆草处理可提高根系数量,扩展根系分布范围至距干0-150 cm内的0-100 cm深土层中;覆膜处理细根总量与水平分布范围较对照有所减小。贮藏营养分别主要贮藏在细根、1 a生枝与粗根中,并以淀粉含量的提高效果最为显著。【结论】覆草可有效增大根系分布范围,提高不同枝条与根系中贮藏营养含量,是陇东旱塬区苹果园较为适宜的地表覆盖方式。

[ Objective ]The effects of different mulching measures （conventional tillage as the control, plastic mulching, and straw mulching ） on apple root distribution and nutrient reserves in different organs of apple trees grown in the dry area of eastern Gan＇su were studied. [Methods ]Fourteen-year-old apple trees were used as the materials and different orders of roots （diameter ≤2 mm, 2-5 mm, 5-10 mm and ≥10 mm） were collected using stratified sampling method from soil profiles to investigate root spatial distribution, root biomass and root length and surface area, and the ratio and dynamic of storage nutrient content in apple roots and branch system measured during the nutrient backflow and redistribution period. [ Results] Roots of the control were distributed mainly in the soil layer at a depth of 30-120 cm with a dis^-1 tance of 0-60 cm from the trunk. Roots were mainly distributed in the soil layer of 0-100 cm in depth and in a distance of 0-150 cm and 0-60 cm from the trunk in the treatments of straw and plastic mulching, respectively. Roots in 20-40 cm from the ground were the most intensive. Plastic mulching narrowed the horizontal root distribution compared wiih the control, but the treatment slightly reduced the amount of total fine root, which was 96.35% that of the control. Thick roots were not significantly changed by plastic mulching, Accumulation of storage nutrient during over-wintering period was significantly improved by both mulching treatments, which most significantly increased starch content, which reached 146.69%- 259.78% and 121.67%-129.83% that of the control in straw mulching and plastic mulching treatments,respectively. The main organs for storage of soluble sugars and starch included the fine roots, thick roots, and annual branches. As a result of rapid soil temperature increase in plastic mulching treatment, the root system became active earlier than that in the other treatments, and thus the rate of nutrient reserve reuti- lization and relocation to the aboveground parts was higher. [Conclusion] Plastic mulching treatment reduced roots distribution significantly, while straw mulching increased root distribution both horizontally and vertically and thus increased the space for absorption of water and fertilizers, which enhanced of the build-up of nutrient reserves in branches and roots. Therefore, straw mulching is recommended as the suitable way of soil management in apple orchards in the dry area of eastern Gansu.