Potassium Phosphite

I. Mechanism of Potassium Phosphite

1. Stage 1
   After application, potassium phosphite can be absorbed by plant leaves and roots, transported within the plant, and exert its direct fungicidal effects. It also activates the plant's disease defense system. When pathogens invade, potassium phosphite stimulates the production of phytoalexins, enhancing the plant's disease resistance.

2. Stage 2
   When pathogens invade, potassium phosphite attacks them, partially controlling their spread. The plant cells recognize the pathogens, triggering the defense system to produce phytoalexins and PR proteins that directly attack the pathogens. Additionally, the plant sends signals to other unaffected cells to activate their defense systems. This process increases polysaccharides and additional proteins, strengthening the cell walls and suppressing or killing the pathogens. The accumulation of phytoalexins is a typical defense response, and potassium phosphite promotes this accumulation, activating phytoalexins to participate in the plant's defense. Chitinase and glucanase, which are pathogenesis-related proteins, also accumulate in leaves, surface wounds, or infected areas, enhancing resistance to diseases like canker.

3. Stage 3
   Potassium phosphite induces the plant to send disease resistance signals to other cells, activating their defense systems. It also stimulates the production of lignin, thickening the cell walls.

From its mechanism, potassium phosphite often acts as a biostimulant rather than directly targeting pathogens. It stimulates the plant's natural defense system, akin to a vaccine in animals. It is absorbed and transported bidirectionally through the xylem and phloem, faster than phosphate-based phosphorus. It activates the production of polyphenols and reactive oxygen molecules, enhancing defense enzyme activity. Regular use significantly improves the plant's stress and disease resistance, promoting root, flower, and fruit development.

II. Uses of Potassium Phosphite

1. Effective Prevention of Canker: At the early stages of infection, normal application can stop canker perforation and prevent the spread of lesions. During severe outbreaks, it can be combined with copper-based sprays for effective treatment. Potassium phosphite is a systemic fungicide with no resistance issues, improving the utilization of other trace elements. It effectively prevents and treats fungal and viral diseases like blight, downy mildew, root rot, and late blight. Regular use enhances disease resistance and stress tolerance. It prevents grape downy mildew, gray mold, and viral diseases while improving leaf flexibility and thickness.

2. Promotes Fruit Expansion: Potassium phosphite regulates and promotes fruit enlargement, coloring, and extends shelf life while improving color quality.

3. Root Growth: Enhances root development, improving water and nutrient absorption.

4. Growth Control: Effectively controls apical dominance, preventing excessive vegetative growth. In citrus and cherry trees, it thickens leaves, promotes spring shoot maturation, and inhibits summer shoot growth while ensuring flower and fruit retention. It is safe for use during spring shoots and young fruit stages without causing phytotoxicity.

5. Flower Promotion: Enhances flower bud differentiation, resulting in fuller, healthier flowers and improved fruit set and quality.

6. Promotes Shoot Maturation and Fruit Greening: Accelerates the maturation of new shoots and the greening of young fruits.

7. Nutrient Supplement: With a high phosphorus and potassium content of 675 g/L, it quickly supplements essential nutrients and trace elements.

III. Characteristics of Potassium Phosphite

1. Rapid Absorption: Absorbed through leaves, roots, xylem, and phloem, it is five times faster than phosphate-based phosphorus. It promotes root growth, controls apical dominance, and ensures timely nutrient supply during peak fruiting periods, improving flower and fruit quality. Its efficacy surpasses that of monopotassium phosphate by three times.

2. Disease Prevention and Control: As a +3 phosphorus-based fertilizer and systemic fungicide, it triggers molecular reactions in plant cells, activating the plant's immune system. The +3 phosphorus inhibits spore formation, altering fungal walls and preventing further proliferation.

3. Systemic Translocation: It is absorbed and translocated bidirectionally, activating polyphenol and reactive oxygen production, and enhancing defense enzyme activity. It treats and prevents internal infections, improving stress and disease resistance. It can be applied via foliar spray, drip irrigation, or drenching for rapid phosphorus and potassium supplementation.

4. Improves Soil Microelement Utilization: When applied to roots, it releases fixed calcium, zinc, and iron, improving soil structure and root health. It is not easily fixed in soil and enhances the absorption of trace elements. It is compatible with most pesticides, copper-based products, and fertilizers without causing precipitation or phytotoxicity.

5. High Safety and Compatibility: It can be mixed with various copper-based products, pesticides, and fertilizers (except strong alkaline products). It is safe for use during spring shoots and young fruit stages without causing phytotoxicity.

IV. Application Methods

1. Foliar Spray: Dilute at 1000x concentration. Apply in the evening under windless conditions, ensuring both sides of the leaves are evenly covered. Apply 2-3 times during the growth cycle.

2. Drip Irrigation or Drenching: Apply 300-500 mL per mu each time, combined with other fertilizers. Apply 2-3 times during the growth cycle.