Effect of dwarfing interstocks on tree growth,yields and fruit quality of ‘Miyazakifuji' apple

Abstract:【Objective】The effects of different mulching measures(conventional tillage as the control, plas-tic mulching, and straw mulching) on apple root distribution and nutrient reserves in different organs ofapple trees grown in the dry area of eastern Gansu were studied.【Methods】Fourteen-year-old apple treeswere used as the materials and different orders of roots(diameter ≤2 mm,2-5 mm,5-10 mm and ≥10mm) were collected using stratified sampling method from soil profiles to investigate root spatial distribu-tion, root biomass and root length and surface area, and the ratio and dynamic of storage nutrient contentin apple roots and branch system measured during the nutrient backflow and redistribution period.【Re-sults】Roots of the control were distributed mainly in the soil layer at a depth of 30-120 cm with a dis-tance of 0-60 cm from the trunk. Roots were mainly distributed in the soil layer of 0-100 cm in depth andin a distance of 0-150 cm and 0-60 cm from the trunk in the treatments of straw and plastic mulching, re-spectively. Roots in 20-40 cm from the ground were the most intensive. Plastic mulching narrowed thehorizontal root distribution compared with the control, but the treatment slightly reduced the amount of to-tal fine root, which was 96.35% that of the control. Thick roots were not significantly changed by plasticmulching. Accumulation of storage nutrient during over-wintering period was significantly improved byboth 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 reutilization 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.