The Effect Of Topography On The Growth Of Mountain Apple And The Control Technology Of Fruit Pre-harvest Dropping In ‘honeycrisp’ Apple

In recent years,Shaanxi mountain apples have developed rapidly and have become the pillar industries for farmers in northern Shaanxi to get rid of poverty.However,the mountain orchard has a complex topography and the microclimate phenomenon is obvious.In this study,the 7a raw‘Honeycrisp’apple tree was used as the test material,and the mountain top,the upper mountainside sunny slope,the upper mountainside shady slope,the lower mountainside sunny slope,the lower mountainside shady slope,the valley and the mountain foot were selected in the mountain‘Honeycrisp’orchard.A typical topography investigates the meteorological factors and the growth and development levels of‘Honeycrisp’apple trees,providing a theoretical basis for the rational management of mountain apple orchards.‘Honeycrisp’fruit has high quality and good economic benefits,but the problem of fruit drop before harvest is serious.In this experiment,Leave fruit with long stalk during fruit thinning at young fruit stage,Sugar alcohol calcium is sprayed in the young fruit stage,and NAA and GA₃ were sprayed one month before harvesting.‘Honeycrisp’pre-harvest fruit drop control.The main findings of the test are as follows:（1）Average temperature,5-25 cm soil temperature and sunshine hours at the top of the mountain in April were 1.3℃,1.6℃and 65 hours higher than those at the foot of the mountain,respectively.Therefore,the initial flowering stage,the full flowering stage and the declining flowering stage at the top of the mountain were 13,14 and 12 days earlier than those at the foot of the mountain,respectively.（2）Frost damage occurs in different topographical locations and phenological periods,resulting in different freezing conditions.The upper mountainside sunny slope was in full blossom stage and was seriously frozen.The survival rates of top flower buds and side flower buds were 0%and 12%respectively.The lower mountainside sunny slope was at the beginning of flowering stage and was lightly frozen.The survival rates of top flower bud and side flower bud were 50%and 44%respectively.Although valleys and foothills did not blossom,the location of valleys and Foothills was low,the temperature was lowest and lasts for a long time during freezing injury,and the freezing was the most serious.The fruit setting rate was the lowest,which is 20%and 14%respectively.The yield per plant was the highest（9.12 kg）in the sunny slope below the hillside and the lowest（1.54 kg）in the foothill.（3）The average temperature,5-25 cm soil temperature and total illumination hours in April-October on the upper mountainside sunny slope were 2.13℃,1.84℃and 292 hours higher than those on the foothill,respectively,and 1.77℃,1.34℃and 177 hours higher than those on the upper mountainside shady slope,so the dry and fresh weight,leaf thickness,leaf area,leaf area index and chlorophyll content of the leaves on the upper mountainside sunny slope were significantly higher than those on the foothill and upper mountainside shady slope.The length of autumn shoots was the longest at the foot（28.54 cm）,shorter at the upper mountainside sunny slope（18.45 cm）and shorter at the lower mountainside sunny slope（16.10 cm）.（4）Fruit shape index of upper mountainside sunny was 0.06 and 0.05 higher than that of foothill and the upper mountainside shady slop respectively,fruit firmness was 1.67kg/cm³ and 1.13 kg/cm³ higher than that of foothill and the upper mountainside shady slop respectively,/and single fruit weight was 7.7%and 3.8%higher than that of foothill and the upper mountainside shady slop respectively.Soluble solids were 3.3%,1.76%higher and acidity was 0.13%and 0.15%lower than that of foothill and the upper mountainside shady slop respectively.The fruit quality of sunny hillside is better than that of shady hillside.（5）Leave fruit with long stalk during fruit thinning at young fruit stage of‘Honeycrisp’,spray sugar alcohol calcium at young fruit stage,spray 40 mg/L of NAA one month before harvest,spray 40 mg/L of NAA and 100 mg/L of GA₃ at the same time one month before harvest,which were 5.17%,9.09%,31.33%and 27.06%lower than CK,respectively.The pre-harvest drop rate of‘Honeycrisp’treated with GA₃ at 100mg/L a month before harvest was 25.66%higher than CK.This may be caused by the discomfort of spraying concentration and spraying time.The best concentration of NAA for preventing fruit drop before harvest was 40 mg/L,and the best spraying time was one month before harvest.（6）The fruit weight of the‘Honeycrisp’,which spraying calcium alcohol at the young fruit stage,was increased by 7.2%,and the acidity was reduced by 12.8%compared with CK.There was no significant difference in fruit quality and CK under NAA treatment.The fruit hardness of GA₃ treatment was significantly higher than that of CK.The fruit shape index was 0.83 when the fruit was thinned during the young fruit period,which was significantly lower than CK（0.88）.The reason is that the fruit with long stalk is mostly edge fruit,while the fruit with short stalk is mostly centre fruit.The edge fruit is not as big as the centre fruit,and there is no high stake in the center fruit.（7）The length of the stalk is one of the reasons for the‘Honeycrisp’before harvest.The peak of the normal curve of the fruit stalk length（18 mm）of the falling fruit was lower than the length of the fruit stalk of the unfalling fruit（20 mm）.The average length of the fruit stalk of the falling fruit was 12.32 mm,and the average length of the stalk of the unfalling fruit was 20.92 mm.