Main Technical Points of Erecting Anti-hail Net in Orchard
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Main Technical Points of Erecting Anti-hail Net in Orchard

Ⅰ. Erection form and planning design of anti-hail net


1. Erection form


There are three main types: ① plane type. It is suitable for orchards with large area and flat terrain. ②Single slope type. Suitable for small orchards in mountainous areas. ③Wave type (double-sided slope type). It is suitable for orchards with flat terrain and high management level.


2. Planning and design


Choose the erection form according to the terrain and orchard area; plan and design based on the principle that the distance between the main poles should not be greater than 70m and the distance between adjacent side poles should be 8-15m. Estimate the quantity, specification and cost of the main pole, side pole, auxiliary pole, main wire, auxiliary wire, ground anchor stay wire and anti-hail nets of different widths.


Ⅱ. Selection of frame material for anti-hail net


1. Anti-hail net


(1) Material performance requirements:


①Light weight, easy to erect, 667m2 anti-hail net weighs about 30kg;


② Anti-aging and anti-ultraviolet rays, the service life can reach more than 5 years;


③ Stable chemical properties, requiring acid resistance, alkali resistance, various chemical corrosion resistance, strong solvent resistance and steam permeability resistance;


④ The structure is reasonable and stable, with strong impact resistance, and it is not easy to produce relative slip deformation during use;


⑤ Strong light transmission, shading rate is less than 10%, does not affect the normal growth of fruit trees.


(2) Specification structure:


The mesh is mainly diamond-shaped, and rectangular or square can also be selected. The diamond-shaped mesh size is 11mm×11mm as the best, and the web width is 6m, 8m, and 12m.


(3) Quantity of purchased anti-hail nets:


The mesh is diamond-shaped, and if the orchard area is less than 0.67hm2 (10 mu), the net area should be 120% of the orchard area; if the orchard area is 0.67-3.33hm2 (10-50 mu), the net area should be 115% of the area; if the orchard area is more than 50 mu, the net area should be 105% of the orchard area.


(4) The color of the net:


Mainly white, black or other colors can be selected above the altitude of 1000m.


2. Rod


There are main rods, side rods and auxiliary rods. Pole height (m) = (tree height + 0.5) × 1.2, the part of the pole that enters the ground must be carbonized or soaked in asphalt.


(1) Main rod. Concrete poles are mainly used, the small head is 6cm×6cm, the big head is 12cm×12cm, and 6-8 steel bars are added, and the main pole can be extended by 20cm if conditions permit.


(2) Side bars. Concrete pole, small head 4cm×4cm, large head 8cm×8cm, and add 4 to 6 steel bars; wooden pole, small head diameter greater than 6cm.


(3) Auxiliary lever. Concrete pole, small head diameter 4cm×4cm, large head 6cm×6cm, and add 4 steel bars; wooden pole, small head diameter greater than 4cm.


3. Wire frame


There are main wires, auxiliary wires and ground anchor wires. The main wires and ground anchor wires must choose stainless steel stranded wires, and 4~6# steel wire ropes are used for auxiliary wires.


4. Suture rope


It is best to choose sewing rope of the same texture as the mesh, or fine wire.


Ⅲ. Steps of erecting the anti-hail net


1. Mark the position of each pole


(1) Main pole. Flat orchards are located at the four corners of the orchard, and mountain orchards are selected according to the terrain.


(2) Side bars. The pole distance of flat orchards is determined by the net width and the distance of the main pole, and the mountain orchard is determined by the terrain and the distance of the main pole.


(3) Auxiliary lever. Each main rod and side rod determine the secondary rods according to the rhombus, square or rectangular diagonal.


(4) Main rod. For the ground anchor hole of the side pole, the angle between the ground anchor line and the ground is 45°, which should not be greater than 75°.


2. Grid rack


(1) Digging rod pits and ground anchor pits. The main pole pit is 70cm deep, the side pole and auxiliary pole pit are 50cm deep, and the ground anchor pit is 100cm deep. The bottom of the pole pit must be solid (especially for orchards that can be irrigated).


(2) Set up the main network. Lower the ground anchor, plant the main pole, and tighten the main wire and the ground anchor line with wire tightening pliers.


(3) Plant auxiliary rods and pull auxiliary wires. After planting and pulling, pull the mesh diagonally. If the distance is far away, you can use a tight wire anchor to tighten it. The top of each pole must be wrapped with a fertilizer bag.


3. Laying anti-hail net


Choose nets of different sizes according to the needs. The length of the rhombus net is 120% of the length of the net frame, and the length of the rectangular or square net is 105% of the length of the net frame. Avoid stitching as much as possible. The net must be laid in a straight line, and both sides are sewed on the main silk or the auxiliary silk at the same time, and the net surface should be flat.


4. Matters needing attention


(1) It is generally erected before the end of May (before bagging), and the nets are unloaded on sunny days after harvesting autumn and winter fruits.


(2) It should be erected under the guidance of professionals, and strive to plan scientifically and rationally, with low cost, good structure and firm network structure.


(3) Choose the frame material according to the type of hail belt and investment capacity in the orchard. For the hail belt with a lot of hail and long duration, choose high-strength grid frame mainly made of cement poles. Others can be lower, and steel materials should not be selected as much as possible.


(4) The bases of various rods must be guaranteed not to sink, and the base plate should be prefabricated as far as possible. Two ground anchors must be placed on the four-corner main pole, and all other main pole side poles should be ground anchored. For mountain orchards, the inner jack rod can be used instead of the ground anchor.


(5) More than 3 people must work together to erect the anti-hail net. Those who are old, have a history of high blood pressure and fear of heights are not allowed to work on the ladder. Note that one must fasten the safety rope, and the other is to fix the ladder.


(6) The anti-hail net should be kept away from fire sources during storage and transportation, and beware of rat bites.

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