1. Symptoms of phosphorus deficiency in plants:
Phosphorus is the main element of the cytoplasm. When plants lack phosphorus, cell division is blocked, crop stems and leaves grow slowly leaves
curl and narrow, leaves are dark green, seriously red, or purple, and root development causes late flowering and insufficient fruit.
2. Type, properties, and application of commonly used phosphorus fertilizer
(1) Calcium perphosphate
Chemical formula: Ca (H2PO4)2· H2O + CaSO4
Short for general calcium, is the world's earliest production of phosphate fertilizer, is also a quick effect of water-soluble phosphate fertilizer, also
known as standard phosphate fertilizer (generally containing P2O5 16% as the standard content).
Gray white or brown white powder into the granular, slightly sour taste, strong hygroscopic, easy to block, to the use of inconvenience.
The main component is calcium phosphate, which is soluble. The aqueous solution is acidic (PH = 5) containing the active ingredient P20516-18％.
Because it contains 3~5% free acid (sulfuric acid and phosphoric acid).
Therefore, there is a certain corrosion, so pay attention to the storage container.
When applied to alkaline soil, monocalcium phosphate is easy to combine with calcium ions in the soil to form dicalcium phosphate, and ocalcium phosphate finally forms decalcium phosphate, thereby reducing the fertilizer efficiency of superphosphate.
2. Application key points:
(1) It is a quick-acting fertilizer, suitable for a variety of soil and crops.
(2) It is appropriate to make base fertilizer, the dosage should account for more than 70% of the total amount of phosphorus fertilizer, should not be directly mixed, a dosage of 3-5 kg/mu.
(3) to the tillage layer and soil, but the effect is not as good as the base fertilizer.
(4) Before and after flowering, it is most suitable for leaf spraying, which can be matched into 0.5-2% solution, spray the leaves, spray once every 7-10 days, and spray 2-3 times. The time is generally sprayed in the evening when there is no wind or rain. Time is generally sprayed in the evening without wind or rain.
(2)Referred to as heavy calcium, also known as three phosphate fertilizer. The main component is calcium phosphate, which does not contain or rarely contains calcium sulfate, so the effective component is high, containing P2O536-52%, which is 2-3 times higher than general calcium.
Gray white particles or powder, soluble quick effect, acid reaction, hygroscopic, corrosion is stronger than calcium, so more attention should be paid to safety.
2. Application method:
It is basically similar to general calcium, but because the concentration is too high, the amount should be reduced by 1/2-2/3 accordingly, because it does not contain calcium sulfate, so the application effect is not as good as general calcium for sulfur-loving crops such as potatoes, beans, cruciferous rapeseed, and other crops, and it is not as good as general calcium in alkaline soil.
(3) Bone powder
It is made of animal bones and crushed, containing P, Si, Ca, and other elements.
It is an insoluble P fertilizer and is often used as a base fertilizer. It is currently less used in production.
Utilization rate of phosphate fertilizer
The utilization rate of phosphorus fertilizer in seasonal crops is the lowest in chemical fertilizers. According to the statistics of 849 test results around China, the general seasonal crop is only 10-25%. Among them, rice is 8-20% and wheat is 6- 26%.
However, the phosphorus fertilizer applied into the soil has not been absorbed by the crops in the season, and about 75-90% of the phosphorus is fixed
by the soil and stored in the soil.