1. Tree management 1. Saplings are fixed and shaped. Proper early drying and low drying are conducive to early formation and early results. Generally, it should be fixed in the period of 2-3 years after planting, and the height of the tree should be fixed at a height of 1 to 1.2 meters. The height of the dryness should be about 80 cm, and all the secondary branches below the fixed position should be removed or a short section should be left. 2. The result tree is trimmed. Follow the principle of “pruning by tree and shaping with branches†to solve the problem of ventilation and light transmission, and moderately double-cut the jujube head of the outer extension branch, so that the growth of jujube head is maintained at about 30 cm per year. The total number of buds on the annual jujube should account for 1/8 to 1/6 of the whole tree.
Second, under the tree management 1, fertilization. Spring fertilization includes early application of base fertilizer and late spring application of quick-acting fertilizer. In late spring, the quick-acting fertilizer is mainly based on nitrogen fertilizer, which is carried out before and after germination in April-May. Each plant is topdressed with 0.5-1 kg of urea and 2 kg of superphosphate. 2, ploughing in the spring. In the spring, the ploughing is carried out after the soil is thawed. The depth of ploughing is 30-40 cm, and the depth near the trunk should be shallow to prevent damage to the roots. 3, spring irrigation. Generally, irrigation is carried out by acupoint irrigation and furrow irrigation. The irrigation in the northern germination period is better, and it is best to combine with topdressing.
Third, pest control 1, scraping bark, spray stone sulfur mixture. It is best to scrape the old bark in the winter and freeze the wintering eggs. In the first ten days of March, the whole tree was sprayed with a 5-wave US stone sulphur mixture to eliminate the source of pests and diseases. 2, wrapped around a plastic apron or coated with shellac. In the middle and late March, a plastic band of 6-10 cm wide or sticky shellac was wrapped around the trunk to prevent pests such as jujube from coming to the tree.
Although there are many types of tapping screws, they all have the following similarities:
(1) are generally made of carbonized carbon steel (accounting for 99% of total production). It can also be made of stainless steel or non-ferrous metals.
(2) The product must be heat treated. Carbon steel tapping screws must be carbonized and stainless steel tapping screws must be solution hardened. In order to make tapping screws to meet the requirements of the standard of mechanical properties and performance.
(3) The product surface hardness is high, the core toughness is good. That is, "soft inside strong outside". This is a major feature of tapping Screw performance requirements. If the surface hardness is low, it can not be screwed into the matrix; If the core toughness is poor, a twist will break, can not be used. So "inside soft outside steel" is self-tapping screw to meet the use of performance, very important requirements.
(4) The surface of the product needs surface protection treatment, generally electroplating treatment. Some product surface must be treated by phosphate (photostatting), such as wall panel self - tapping screws for photostatting.
(5) Production by cold heading process. It is recommended to use high-speed cold heading machine and high-speed wire rolling machine or high-speed planetary wire rolling machine. High speed is emphasized here to ensure product quality. Only the head of tapping screw produced by high-speed machine is well formed and the thread quality is high.
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