Study On The Techniques Of Cutting Roots And Spraying Pro-calcium Acid To Regulate The Growth Of Apple Trees

The cultivation mode of the dwarf stock dense planting is the development direction of apple industry in the world.At present,China is in the transition period from dense planting of arbor stock to close planting of dwarf stock.Tree control is the key to the success of close planting of dwarf stock.Apple tree regulation is mainly achieved by using dwarfing rootstock,pruning technology,spraying plant growth regulators and other technologies,but due to the need for special machinery,the traditional crown pruning technology is less applied to the root pruning of the underground part.PBO is often used in chemical control production,but its degradation is slow and its residual period is long.If it is not used properly,it is easy to cause serious side effects.As a new type of plant growth retardants,Pro-calcium Acid has the characteristics of safety,high efficiency,environmental protection,short residual period and low residue.The experiment is conducted to study the effects of root cutting and spraying of Pro-calcium Acid on the growth of apple trees,which bases on the Malus robusta as the base stock and "Tianhong No.2" with SH40 as the intermediate stock,aiming to provide a more efficient and safe method for the control of apple trees with dwarf rootstocks.The major findings of the experiment are as follows:1.Appropriate root cutting treatment effectively inhibits the growth of young trees and adult trees.Among the single and double side root cutting treatments with 50cm,60cm,70cm and 80cm away from the trunk,the effect of bilateral 50cm root cutting is the most prominent.The trunk diameter,tree height,branch spread and super long branch number of young trees are significantly reduced by 17.9%,12.1%,25.7%and 77.7%respectively compared with the control.The trunk diameter and autumn shoot length of adult trees are reduced by 25.2%and 60.2%respectively.On the whole,the inhibition effect of bilateral treatment is greater than that of unilateral treatment,and the root-cutting distance has an opposite trend to the inhibition effect.What’s more,when the distance of root cutting is 50～70cm away from the trunk,the effect is more obvious.2.Foliar sprayed Pro-calcium Acid can significantly inhibit the growth of apple shoots.For 6-year-old trees,it has the best economic benefit and inhibiting effect when sprayed 175ppm once before spring shoots growth(5.1)or sprayed 125ppm twice before the spring and autumn shoots growth(5.1).6.15).For 3-year-old young trees.spraying 300ppm once at the early stage of spring shoot growth(5.1)or spraying 150ppm once before the growth of spring shoots and autumn shoots(5.1,6.15)has the best economic and inhibitory effects.3.In the range of 25ppm～175ppm,when the concentration of Pro-calcium Acid is higher than 125ppm,the leaf thickness increases.while the leaf area become smaller and the petiole become shorter.Spraying different concentrations of Pro-calcium Acid can promote the increase of chlorophyll content in apple leaves.The chlorophyll content of apple leaves is increased by 14.9%compared with the control when the concentration of Pro-calcium Acid is 150 ppm.And there is no significant effect on the fruit quality of the same year and the next year in this range.4.The Fv/Fm value decreases first and then increases within 30 days after spraying Pro-calcium Acid,while Fv/Fm value shows a downward trend when PBO is sprayed 150 times.The Fv/Fm value is significantly higher than that of the control when the concentration of Pro-calcium Acid is higher than 150 ppm,and the Fv/Fm value is the highest when the concentration is 300 ppm.The result shows that spraying the appropriate concentration of Pro-calcium Acid can increase the maximum photochemical efficiency of leaves,promote the transfer of photosynthetic electron transfer and the utilization efficiency of light energy..5.The effect of spraying different concentrations of Pro-calcium Acid on endogenous hormones in apple leaves is studied in the experiment.The result shows that spraying different concentrations of Pro-calcium Acid can reduce the content of endogenous hormones GA3,IAA and ZR in apple leaves when compared with the control,and increase the content of ABA,while the content of GA3,IAA,ZR and ABA in the treatment of 150 times PBO is between 150 ppm and 300 ppm of Pro-calcium Acid.6.There is no significant effect of foliar spraying with different concentrations of Pro-calcium Acid on the yield of that year.When the spraying concentration is 175 ppm,it can significantly increase the next year’s flower amount of apple trees,which increases by 27.7%compared with the control.Compared with the control,the yield of the current year and the amount of flowers in the next year decrease significantly by 30.7%and 25%respectively after 6 times of spraying.7.There is no significant difference in leaf length,leaf width,petiole length and leaf area between spraying 300 ppm Pro-calcium Acid 6 times and spraying 150 times PBO in the same year.While in the next year.the leaf length.leaf width.petiole length and leaf area of 150 times PBO treatment are significantly reduced by 36%.37.2%,24.6%and 56.3%compared with spraying 300 ppm Pro-calcium Acid for 6 times,and the leaf surface is in the state of curling.Spraying 300 ppm Pro-calcium Acid for 6 times has no significant effect on the fruit quality of the next year,while the hardness and soluble solid content of 150 times PBO treatment increase by 17.1%and 9.7%compared with the control,but the weight of single fruit,titratable acid content,fruit compared with the control,the length of the shank was significantly reduced by 45.4%,38.2%,and 74.3%.In conclusion,As a new plant growth regulator,Pro-calcium Acid is more ideal than PBO.