TMAP vs. TDAP: Chemistry, Application, and Global Trends

Monoammonium Phosphate (MAP) and Diammonium Phosphate (DAP) are both ammonium phosphate fertilizers synthesized by neutralizing phosphoric acid with ammonia. These two types of phosphate fertilizers share several features: they are water-soluble, contain high levels of phosphorus and ammoniacal nitrogen, possess excellent physicochemical properties, and are readily absorbed by plants, offering high fertilizer efficiency.

They can be applied alone as base or topdress fertilizers and also serve as raw materials for compound and blended fertilizers. Together, they represent the most widely produced and applied phosphate fertilizers globally, accounting for about 90% of total phosphate fertilizer production.

Basic Information

Item	MAP (Monoammonium Phosphate)	DAP (Diammonium Phosphate)
Common Name	Monoammonium Phosphate / Monoammonium Dihydrogen Phosphate	Diammonium Phosphate / Ammonium Hydrogen Phosphate
CAS No.	7722-76-1	7783-28-0
Chemical Formula	NH₄H₂PO₄	(NH₄)₂HPO₄
Appearance	White crystalline powder	Grey-white to dark grey granules
Solution pH (0.1mol/L)	Acidic, pH 4.4–4.8	Weakly alkaline, pH 7.8–8.2
Solubility (20°C)	37.4 g/100mL	41 g/100mL
Nutrient Grades (N-P-K)	11-44-0 / 10-50-0 (Agri), 12-61-0 (Tech)	18-46-0 (Agri), 21-53-0 (Tech)

Table 1. Physicochemical Properties Comparison

Property	MAP	DAP
Chemical Formula	NH₄H₂PO₄	(NH₄)₂HPO₄
Crystal Structure	Orthorhombic	Monoclinic
Nitrogen Content (N%)	12.2	21.2
Phosphorus Content (P₂O₅%)	61.8	53.8
N:P₂O₅ Ratio	1:5.1	1:2.5
Density (g/cm³, 20°C)	1.803	1.619
Melting Point (°C)	190.5	Decomposes
Enthalpy of Formation (kJ/mol)	−1451	−1574
Heat of Solution (kJ/mol)	16	14
Heat of Fusion (kJ/mol)	35.6	—
Critical Relative Humidity (30°C)	91.6%	82.5%
pH (0.1mol/L solution)	4.4	8.0
Solubility (g/100mL, 20°C)	39.5	68.9

Key Differences in Properties

• MAP has better thermal stability and a high melting point. It resists decomposition even at 190°C, has high critical humidity, low hygroscopicity, and excellent solubility.

• DAP, however, is less thermally stable. It decomposes slowly above 80°C, releasing one ammonia molecule and converting into MAP. It is more hygroscopic and prone to caking during storage and transport.

Application Differences

1. Nutrient Composition

• MAP has higher phosphorus but lower nitrogen than DAP due to its single ammonia molecule.

• DAP has higher nitrogen content and a more balanced N:P ratio, suitable for crops requiring more nitrogen.

  
  

2. pH Impact

• DAP is weakly alkaline (pH ~8). When mixed with calcium-rich materials (e.g., superphosphate or lime), it can form insoluble calcium phosphate, reducing phosphorus availability.

• MAP is weakly acidic (pH ~4.4), avoiding this reaction and retaining more available phosphorus, especially beneficial in calcareous soils.

  
  

3. Soil Suitability

• MAP slightly acidifies the soil solution, enhancing phosphorus uptake and reducing ammonia volatilization when mixed with nitrogen fertilizers like urea.

• DAP may raise pH and cause ammonia loss in alkaline soils, particularly under high temperatures or poor ventilation, potentially harming young seedlings.

Recommended Usage Scenarios

Use Case	MAP	DAP
Thermal Stability	High	Low
Moisture Sensitivity	Low, suitable for powder/granules	High, only granules
Suitable Soil	Acidic to neutral	Neutral to alkaline (avoid high-Ca soils)
Best Use	Base + Topdressing + Blending	Base fertilizer mainly
Crops	Fruits, vegetables, flowers	Grains (wheat, rice, maize)

Manufacturing Differences

1. MAP production is more energy-efficient. Reaction heat doesn't cause significant ammonia loss. High-pressure jet neutralization is highly efficient.

2. DAP requires more careful temperature and ammonia control to prevent ammonia volatilization and conversion into MAP. Yields are lower, and costs are higher.

3. Raw Material Tolerance: MAP tolerates lower-purity phosphoric acid (e.g., containing Mg, Fe, Al). DAP requires purified acid made from high-grade phosphate rock (>30% P₂O₅).

Storage and Transport

• MAP is denser and more stable with a higher critical humidity. Less prone to caking, even in powder form. Suited for long-term storage.

• DAP is thermally unstable, sensitive to moisture, and may degrade under direct sunlight. Always stored as granules. Proper storage conditions are critical to maintain quality.

Application Methods & Precautions

Category	MAP	DAP
Base Fertilizer	15–25 kg/mu (deep placement, mix with organics)	20–30 kg/mu (broadcast before plowing)
Topdressing	Strip, hole, or fertigation (avoid root burn)	Not recommended
Seed Fertilizer	Not suitable	Maintain 3–5 cm distance from seeds
Mixing Warnings	Avoid mixing with alkaline materials, Cu/Zn ions	Avoid acids, Ca/Mg fertilizers, acid pesticides

Global Market Trends

• From June 2024 to May 2025, phosphate fertilizer prices showed high-level fluctuations.

  • Mid-2024: FOB price for DAP and MAP: $600–750/ton.

  • Early 2025: Dropped to $550–650/ton.

  • Apr–May 2025: DAP spot price in the US rebounded to $700–800/ton; Brazil MAP CFR at $650–680/ton.

    
    

• Regional Highlights:

  • USA: Low inventory and tariffs lifted DAP prices.

  • Brazil: MAP prices pressured by FX and import dependency.

  • India: Forced long-term contract DAP prices lower.

  • Europe: Weak demand due to supply chain reshuffling.

Forecast for H2 2025: Global prices expected around $600–750/ton, with an 8% decline in trade volume but a 12–15% increase in average prices due to policy and climate factors.

Summary

While both MAP and DAP are vital ammonium phosphate fertilizers, their core differences lie in:

• Physicochemical Properties: MAP is acidic, high in phosphorus, and thermally stable. DAP is alkaline, nitrogen-rich, and sensitive to heat.

• Applications: MAP is more flexible, usable across soil types and crops. DAP is best for nitrogen-demanding crops in neutral to acidic soils.

• Production & Storage: MAP is easier and cheaper to produce and store. DAP requires more control and care in manufacturing and storage.

Choose wisely based on soil pH, crop needs, and local market factors to achieve optimal fertilizer efficiency.

🏁 Final Message from Kelewell

At Kelewell, we are committed to providing high-quality raw materials and products for modern agriculture. Our ammonium phosphate product offerings include:

• MAP (12-61-0) in 25kg Neutral English Bags

• DAP (21-53-0) in 8kg Neutral English Bags

We welcome technical discussions, documentation requests, and customized solutions to support your product development and regulatory compliance needs.

📩 For inquiries or sample requests, please feel free to contact us.