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Product Name: Monopotassium Phosphite

Fertilizer Grade: 0-58-38

Chemical Formula: KH₂PO₃

CAS Number: 13977-65-6

Molecular Weight: 120.086

Product Overview

Monopotassium phosphite (MKPI or MIKP) is a novel, high-purity inorganic phosphorus-potassium fertilizer that combines plant nutrition with biostimulant functions. Its unique “fertilizer-meets-fungicide” characteristic makes it widely applicable in modern agriculture; it not only supplies the high concentrations of phosphorus and potassium required for crop growth but also offers significant benefits in disease prevention, immunity enhancement, and growth regulation.

Key Advantages

Dual Functionality: Nutrition + Fungicidal Action

High-Efficiency Nutrition: Contains up to 58% phosphorus pentoxide (P₂O₅) and 38% potassium oxide (K₂O), providing crops with ample phosphorus and potassium to promote root development, fruit expansion, and sugar accumulation.

Natural Fungicidal Action: Phosphite ions possess direct fungicidal activity, offering significant control against Oomycete diseases (such as downy mildew, Phytophthora blight, late blight, and root rot) and certain fungal diseases (such as grey mould, powdery mildew, and canker). It stimulates the production of phytoalexins, activating the plant’s own immune system—acting essentially as a “vaccine” for the crop.

High Absorption Rate and Stability

Excellent Foliar Absorption: Compared to traditional phosphates, phosphite molecules are smaller and more easily absorbed through leaf stomata and the cuticle, resulting in higher utilization efficiency.

Slow-Release Effect: Upon entering the plant or soil, phosphite gradually oxidizes into phosphate, ensuring a continuous and stable supply of phosphorus while preventing nutrient loss or fixation associated with single-application fertilization.

Resistant to Soil Fixation: It exhibits high mobility in the soil and is not easily fixed by ions such as iron or aluminium, thereby enhancing phosphorus availability.

Excellent Compatibility

Compatible with most pesticides (including copper-based products), insecticides, herbicides, and fertilizers containing secondary or micronutrients; causes no precipitation or antagonistic reactions.

Particularly suitable for tank-mixing with plant growth regulators (such as brassinosteroids) to achieve an integrated management strategy combining disease prevention, nutrition, and growth promotion.

Environmentally Friendly and Safe

Residue-free and eco-friendly; complies with standards for green agriculture and organic farming.

Low in chloride and sodium, and free from heavy metal impurities; suitable for salt-sensitive crops.

Key Technical Specifications

| Item | Specification |

| Appearance | White crystalline powder |

| Main Content (as KH₂PO₃) | ≥ 98.0% |

| Phosphorus Pentoxide (P₂O₅) | ≥ 58.0% |

| Potassium Oxide (K₂O) | ≥ 38.0% |

| Water-insoluble Matter | ≤ 0.3% |

Application Areas and Recommended Usage

1. Cash Crops (Citrus, grapes, strawberries, tomatoes, etc.)

Shoot Control & Flower Promotion: During the autumn shoot stage of fruit trees (e.g., citrus, mango), spray with a 1000–1500-fold dilution to inhibit excessive vegetative growth and promote flower bud differentiation.

Disease Prevention & Yield Enhancement:

Citrus Canker/Anthracnose: Apply a 1000-fold dilution mixed with copper-based products or specialized fungicides; spray 1–2 times at 7–10 day intervals.

Grape Downy Mildew: Apply a 1000-fold dilution mixed with brassinosteroids; spray evenly, ensuring thorough coverage of the undersides of the leaves. Strawberry/Tomato Late Blight & Grey Mould: Apply as a foliar spray or via drip irrigation at a 1,000–1,500-fold dilution to enhance plant resistance, improve fruit quality, and increase sweetness.

2. Field Crops (Rice, Wheat, Corn, Peanuts)

Disease and Stress Resistance: Apply a 1,000–1,500-fold dilution spray—combined with pest and disease control measures—during critical growth stages (e.g., rice jointing/booting, wheat flowering/grain-filling, or corn “large bell-mouth” stage). This effectively prevents sheath blight, rust, and aphids, while increasing thousand-grain weight and overall yield.

Rooting and Seedling Strengthening: Application during the seedling stage promotes deep root development and enhances drought and cold tolerance.

3. Vegetables and Cucurbits

Cucurbit Downy Mildew/Powdery Mildew: Spray with a 1,000-fold dilution; this significantly reduces disease incidence, especially during seasons characterized by high temperature and humidity.

Solanaceous Crop Blight/Root Rot: Apply via fertigation (drenching or drip irrigation) at 7.5–15 litres per hectare during the early growth stages, followed by foliar spraying in later stages to prevent soil-borne diseases.

Precautions

Oxidative Conversion: Potassium phosphite must undergo oxidative conversion into phosphate to fully function as a phosphorus fertilizer; therefore, in cases of severe phosphorus deficiency requiring immediate supplementation, it is recommended to use it in conjunction with traditional potassium dihydrogen phosphate.

Storage Conditions: Store in a well-ventilated, dry area to prevent moisture absorption and caking. Do not store alongside strong oxidizing or reducing agents.