Corn science fertilization should focus on four aspects.
First, the principle. In fertilization, we should grasp the application of nitrogen, phosphorus, potassium and trace elements, balance fertilization, deep application of fertilizer, staged topdressing, water and fertilizer combination, and improve fertilizer efficiency. In terms of fertilization amount, it should be considered comprehensively according to various factors such as the fertilizer absorption rule, yield level, soil fertility capacity, fertilizer nutrient content and utilization rate.
Second, the base fertilizer. The fertilizer applied before sowing is called base fertilizer. Generally, organic fertilizer, compound fertilizer or part of nitrogen fertilizer, potassium fertilizer and micro-fertilizer are mixed and concentrated in the ditch. If it is too late to apply, it can be applied once as a seedling.
Third, the seed fertilizer. When planting, the fertilizer applied next to the seed or along with the seed is the seed fertilizer. It can satisfy the needs of nutrients in the early stage of corn growth, and promote the development of the lineage and the growth of seedlings. Generally, diammonium phosphate or compound fertilizer and urea 3 kg per mu should be used as a fertilizer, and the fertilizer should be isolated to prevent injury.
Fourth, topdressing. The fertilizer applied during the growing period of corn is topdressing. The period, frequency and quantity of topdressing should be based on the law of corn absorption, the level of production, the geographical basis, and the peak period of demand. At this time, if the supply of nutrients is insufficient, there will be falling flowers and fruit. Malnutrition can also affect the normal development of flower organs and fruits. If pollen is small and the style is slender and uneven, it can not be pollinated and shedding.
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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