Abstract:【 Objective 】 Using Tunisia Soft-seed pomegranates as experimental materials, we performed 21 treatments, taking 7 physical protection measures under 3 soil thickness. The temperature and humidity changes of Tunisia Soft-seed pomegranate trees under various physical measures were measured, and the heat preservation effects of different measures were studied. In this paper, the freezing damage of Tunisia Soft-seed pomegranate of different tree ages was studied, with the freezing damage grade formulated. Moreover, the different freezing damage levels were analyzed, and the rules of freezing damage were combed. Eventually, the anti-freezingcultivation modes were summarized, as a resuilt, we could provide guidance for production practice. 【Methods】Seven kinds of physical protection measures under three kinds of covering soil thickness were taken in the experiment, with a total of 21 treatments, during which all of Tunisia Soft-seed pomegranate trees were entirely covered with soil. There were 3 creeping cultivated 'Tunisia Soft-seed 'pomegranate seedings under each treatment, and the 'Tunisia Soft-seed 'pomegranate seedlings planted in the open field without any protection measures were used as the control group. The daily minimum temperature, daily temperature variation amplitude, daily maximum temperature, daily mean temperature and air relative humidity of soft-seeded pomegranate were compared and analyzed. The daily variation of temperature around the trees treated with different cold-proof measures was compared when the extreme minimum temperature (December 31) occurred.3-year-old pomegranate 'Tunis Soft-seed' were utilized as the experimental materials. 5 kinds of cold-proof measures were set in Company 20 cold sheds and 2 kinds of cold-proof measures were set in Company 19 cold sheds to investigate and analyze the freezing damage of pomegranate trees in the following spring so as to screen the suitable cold-proof and overwintering measures. 【Results】The winter temperature in southern Xinjiang is relatively low, and the cold-proof effect of the traditional buried soil method is not so good. 'Tunis Soft-seed' pomegranate trees still suffer from severe freezing damage, and the frozen parts are mainly the root necks and branches. The older the tree, the lighter the degree of freezing damage. Through this experimental study, it was concluded that the seven physical protection measures could effectively increase the daily average temperature around the ' Tunisia Soft-seed ' pomegranate trees, reduce the daily maximum temperature, daily temperature variation amplitude, and the temperature difference, greatly increasing the relative humidity of the air in the tree microenvironment. The relative humidity was close to 100 %. The thicker the covering soil was, the gentler the daily temperature change was, and the smaller the temperature difference between the tree microenvironment under different covering materials was. It can be seen that by covering the buried soil cold-proof layer, the fluctuation of the tree microenvironment temperature with time can be effectively reduced, thereby increasing the micro-domain temperature and reducing the daily range. Among the seven kinds of physical protection measures, the cold-proof measures of straw curtain + covering soil, straw curtain + steel rebar holder + covering soil and straw curtain + plastic membrance + covering soil had better effects on the safe overwintering of soft-seed pomegranates, obviously increasing the daily average temperature and daily minimum temperature of pomegranate tree microenvironment. In the field freezing damage investigation experiment, the ' Tunisia Soft-seed ' pomegranate trees covered by straw curtain + plastic membrance+ covering soil 15 cm cold-proof measures had the lightest overall freezing damage (freezing damage index 8.3 ). The best physical protection measure among the different covering methods in the cold sheds was straw curtain+arched shed, none of the 'Tunisia Soft-seeded' pomegranate seedlings were frozen, and the physical protection measures that were more effective were respectively felt (freezing damage index 11.0) and soil cover (freezing damage index 17.3).Burying' Tunisia Soft-seed ' pomegranate seedlings under the soil to overwinter in the cold sheds can reduce the degree of freezing and drought, which is a more effective physical protection measure.【Conclusion】The winter climate of Xinjiang is very cold. Even with the traditional cold-proof measure of soil cover, 'Tunisia Soft Seed' pomegranate still suffered severe freezing damage. It is necessary to take other physical protection measures combined with covering soil to avoid freezing damage. The freezing damage of Tunisia Soft-seed pomegranates covered with straw curtain + plastic film + soil covering 15cm cold-proof measures was the lightest (frost damage index 8.3%), which could be popularized and applied. The cultivation of cold sheds alone does not have a good anti-freezing and drought-resistant effect on Tunisia Soft-seed pomegranate trees, and the construction of small arches in cold sheds and the covering of grass curtains on them can ensure the safe overwintering of soft-seeded pomegranate trees.
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