Detailed Explanation of Common Fertilizer Types and Dosages for Foliar Application
Urea The pure product is white crystals, while the industrial product is small white or light yellow granules, with a nitrogen content of 44-46%. It has low hygroscopicity and is easily soluble in water. It is a neutral fertilizer and is the variety with the highest nutrient content among solid nitrogen fertilizers. Because it is absorbed quickly through leaves, has a high utilization rate, and greatly increases yield, it is most suitable for foliar application. The spray concentration should be determined according to the crop type and season, and its range is roughly as follows: for gramineous crops, such as rice, wheat, corn, and cotton, the suitable concentration is 1-2%; for vegetables, such as cucumber, eggplant, watermelon, and potato, the suitable concentration is 0.5-1.5%; for spraying seedlings in hotbeds, the concentration is 0.1-0.3%.
Superphosphate It is a grayish-white powder with a slight sour odor, easily absorbs moisture, cakes, and is corrosive. It generally contains 12-20% phosphorus, is soluble in water, and is an acidic quick-acting phosphorus fertilizer.
Preparation method of superphosphate solution: first take 10 kg of superphosphate and add 100 kg of water to make a 10% stock solution. After adding water, stir thoroughly and let stand overnight. After the insoluble matter settles, take the supernatant liquid and dilute it with water according to the required concentration. For gramineous crops, such as wheat, millet, rice, etc., the spray concentration is 1.5-3%.
????Potassium Dihydrogen Phosphate White or grayish-white crystals, containing 52% phosphorus and 34% potassium. It has low hygroscopicity, is soluble in water, and its aqueous solution is acidic. It is a high-concentration quick-acting phosphorus-potassium compound fertilizer. Due to its high price, it is currently mostly used for foliar application. This fertilizer is mainly sprayed on field crops, such as wheat and corn, during the jointing to booting stage. The suitable concentration is 0.2-0.3%, sprayed once every 5-7 days, and it should be sprayed continuously 2-3 times during the fertilization period, with good yield-increasing effects.
Boric Acid White crystalline powder, generally containing 17% boron, easily soluble in water, with a smooth feel when rubbed by hand. It is a quick-acting boron fertilizer and is suitable for foliar application. It should be applied only when soil and crop boron deficiency is clearly identified, and excessive application must be avoided. For corn, soybean, etc., the suitable spray concentration is 0.1-0.15%; for Chinese cabbage, radish, lettuce, celery, etc., the spray concentration is 0.05-0.1%.
?Borax White crystals, containing 11% boron, easily soluble in water, with a rough, astringent feel when rubbed by hand, which is the best way to distinguish it from boric acid. It is one of the commonly used boron fertilizers and can be used for foliar application. It should be applied only when soil and crop boron deficiency is clearly identified. For corn, soybean, etc., the suitable concentration for foliar spraying is 0.1-0.25%; for Chinese cabbage, radish, celery, lettuce, etc., the spray concentration is about 0.1%.
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