Rock Phosphate - 100% Organic Fertilizer agricultural grade

Rock Phosphate (RP) is a natural, mined ore used both as a direct-application fertilizer and as the primary raw material for manufacturing water-soluble phosphate fertilizers like SSP, TSP, and DAP. Its effectiveness depends heavily on its origin and specific properties.

Detailed Specifications for Rock Phosphate Fertilizer

1. Chemical Composition and Analysis

Rock Phosphate is primarily valued for its phosphorus content, but its full chemical profile determines its effectiveness.

1. Total Phosphate Pentoxide (P₂O₅): Typically ranges from 28% to 36%. This represents the total phosphorus content in the ore.
2. Citrate Soluble P₂O₅: This is the "available" phosphorus for plant uptake and is a key indicator for direct application. It typically ranges from 2% to 8% for most direct-application grades. Higher reactivity is better.
3. Calcium Oxide (CaO): A major component, acting as a secondary nutrient. Content is usually between 35% and 50%.
4. Silicon Dioxide (SiO₂): Essentially inert filler, commonly between 5% and 20%.
5. Fluorine (F): A natural constituent of the apatite mineral, usually present at 2.5% to 4.0%. This is removed during industrial processing.
6. Iron and Aluminum Oxides (Fe₂O₃ + Al₂O₃): Combined content is typically 2% to 6%. High levels can reduce the solubility of the phosphate.
7. Magnesium Oxide (MgO): Present as a secondary nutrient, usually between 0.5% and 2.0%.
8. Sulfur Trioxide (SO₃): Can be present from 1% to 3%, providing a minor sulfur benefit.
9. Heavy Metals: Trace amounts of cadmium, lead, arsenic, etc., must be within the legal limits of the destination country's fertilizer regulations.

2. Physical Properties

1. Form and Appearance: A fine, free-flowing powder. The color can vary from gray to brown, black, or yellowish.
2. Fineness: For direct agricultural use, it is finely ground. A common specification is that a minimum of 80% to 90% of the material must pass through a 100-mesh sieve (150 microns). This fineness is critical for increasing its surface area and reactivity in the soil.
3. Moisture Content: Maximum moisture is typically 3% to 5% to prevent caking and ensure easy handling.
4. Solubility: It is insoluble in water. Its value as a direct fertilizer comes from its solubility in weak soil acids or in citric/formic acid solutions, which is a standard test for its "reactivity."

3. Reactivity and Types

The agronomic effectiveness is categorized by its reactivity:

1. High-Reactive Rock Phosphate (HRRP): Sourced from specific deposits (e.g., in North Africa). It has high solubility in neutral ammonium citrate or 2% formic acid (often >20% of total P₂O₅). This type is suitable for direct application on acidic soils.
2. Low-Reactive Rock Phosphate (LRRP): Has lower citrate solubility. It is less effective for direct soil application and is primarily used as a feedstock for manufacturing water-soluble phosphate fertilizers like SSP (Single Super Phosphate) and TSP (Triple Super Phosphate).

4. Key Agronomic Considerations

1. Soil pH: It is most effective in acidic soils with a pH below 5.5-6.0. In neutral or alkaline soils, it remains largely unavailable to plants.
2. Application: It is a slow-release fertilizer, best applied during land preparation and for long-duration crops like pastures, perennial grasses, and tree plantations.
3. Benefits: Provides a long-term phosphorus source, supplies calcium, and can help improve soil health over time.