Appropriate application of phosphate fertilizer in phosphorus-deficient soil has a good effect on improving the yield and quality of crops. Some farmers' friends mistakenly believe that the more phosphate fertilizer is applied, the better. In fact, excessive application of phosphate fertilizer is not only unhelpful, but also harmful.
First, the application of excessive phosphorus fertilizer will cause the crop to absorb too much phosphorus nutrition from the soil. Excessive phosphorus nutrition will promote the respiration of crops too strong, the dry matter consumed is greater than the accumulated dry matter, causing the reproductive organs to develop ahead of time, causing premature crop maturity, small grain and low yield.
The second is to induce zinc deficiency in the soil. Excessive application of calcium phosphate will cause zinc in the soil to interact with excessive phosphorus, resulting in zinc phosphate precipitation, which can not be absorbed by the crops, causing obvious zinc deficiency symptoms in the crops; excessive application of alkaline magnesium phosphate such as calcium magnesium phosphate fertilizer will cause soil alkali It reduces the effectiveness of zinc and affects the absorption of zinc by crops.
Third, excessive phosphorus application will cause the crop to lose phosphorus. According to the study, excessive application of phosphate fertilizer will also cause the silicon in the soil to be fixed and not absorbed, causing the crop to be deficient in silicon, especially for the grass crops of Si. If you can't absorb more silicon from the soil, if you can't absorb more silicon from the soil, you will suffer from silicon deficiency, such as slender stems, lodging and poor disease resistance.
Fourth, excessive phosphorus application will result in phosphorus deficiency in the crop. Appropriate application of phosphate fertilizer will promote the absorption of molybdenum by crops. However, excessive application of phosphate fertilizer will cause the phosphorus and molybdenum to lose nutrient balance, affecting the absorption of molybdenum by crops, and exhibiting “molybdenum deficiencyâ€.
The fifth is the accumulation of harmful elements in the soil. Phosphate fertilizer is mainly derived from phosphate rock, which contains many impurities. These include harmful elements such as cadmium, lead and fluorine. Moreover, the application of phosphate fertilizer will cause an increase in cadmium in the soil, and its annual growth rate is 0.15% and 0.08%, respectively, and the cadmium has high effectiveness and is easily absorbed by crops, causing harm to humans and animals.
Sixth, excessive application of phosphate fertilizer will cause deterioration of soil physical and chemical properties. Superphosphate contains a large amount of free acid and is applied in large quantities continuously, which causes acidification of the soil. Calcium magnesium phosphate contains 25%-30% lime. Large amounts of application can exacerbate soil alkalinity and deteriorate physical and chemical properties.
So what is the amount of phosphate fertilizer applied? Generally speaking, even in the case of phosphorus-deficient soil, the application rate per acre should not exceed 40 kg, preferably 30-35 kg.
Set screw is also called head screw and positioning screw. The utility model is a screw specially used for fixing the relative position of machine parts. Type: square flange end set Bolt, GB / t821-1988 square chamfered end set screw, GB / t85-1988 square long cylindrical end set screw, inner square head set screw, etc.
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Hexagon socket set screw, hexagon flat set screw, hexagon cylindrical set screw.
The selection of common set Screws is generally used to fix the relative position of two parts with little force. The axial and circumferential positioning of common sleeve like parts on the shaft. There are many kinds of set screws. The common ones are as follows: according to the end part, there are conical end, flat end, concave end, oblong cylinder head, etc;
According to the head part: slotted, hexagon socket, square head, etc. Tapered end screws and concave end screws with sharp ends can be used to directly top the parts, and the concave end is more reliable and can bear greater force; Taper end screws without sharp points must be drilled in the parts. The flat end is used to top the tight plane, which does not damage the parts, but bears limited load.
Slotted screws have small tightening force and are often easy to screw off. Generally, they prefer hexagon socket head; The tightening force of square head is the largest, but it can not be embedded in parts, and its use is limited. In order to prevent loosening and withdrawal of threaded parts, a set screw can be drilled at the cross seam. The long cylindrical head screw at the top end is used in the keyway of the shaft to lock and prevent circumferential rotation. It can also be used in general unimportant occasions when the key slides in the keyway of the shaft.
Set Screws,Allen Nose Set Screw,Slotted Head Set Screw,Hexagon Socket Grub Screw
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