Diammonium Phosphate (DAP) (18-46-0) Calculator & Dosage Guide

Diammonium Phosphate is the world's most widely used phosphorus fertilizer, combining high phosphorus content with ammoniacal nitrogen for initial root development.

Nitrogen18N
Phosphate46P₂O₅
Potash0K₂O
Solubility:588 g/L
Standard Temp:20°C

Pre-configured Diammonium Phosphate (DAP) Calculator

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Calculated Recipe Output

Configure your targets and click "Run Analysis" to generate your fertilizer recipe.

1. What is Diammonium Phosphate (DAP)?

Diammonium Phosphate (DAP) is a high-grade chemical source supplying essential plant nutrients. The standard NPK ratio of this fertilizer is 18-46-0, which signifies that it contains 18% Nitrogen (N), 46% Phosphorus as P₂O₅, and 0% Potassium as K₂O by total product weight. Under agronomic standards, the phosphorus and potassium components are expressed in their oxide forms rather than elemental phosphorus and potassium.

When dissolved in water, this fertilizer dissociates into plant-available ionic nutrients. This allows roots to absorb them instantly via active transport. Understanding the exact composition prevents chemical lockouts and guarantees optimal nutrient concentrations.

2. Best Used For

This fertilizer is highly effective when applied to crops and systems requiring quick, specific nutrient supply:

  • Wheat
  • Maize (Corn)
  • Rice
  • Soybean
  • Potato

3. Solubility & Mixing Instructions

At a standard temperature of 20°C, the maximum solubility limit of Diammonium Phosphate (DAP) is 588 grams per liter of water. Attempting to mix at concentrations above this threshold will result in precipitation, leaving undissolved particles at the bottom of your reservoir or mixing tank.

Step-by-Step Dissolution Method

  1. Fill your clean mixing vessel or reservoir with 70% of the total target water volume.
  2. Using a digital scale with at least 0.1g precision, weigh out the required amount of Diammonium Phosphate (DAP) calculated above.
  3. Gradually pour the dry fertilizer granules into the water while continuously agitating or stirring.
  4. Stir until the crystals are completely dissolved, then top off the vessel with water to reach the final 100L volume.
  5. Measure the Electrical Conductivity (EC) or Total Dissolved Solids (TDS) using a calibrated meter to verify target ppm.

4. Chemical Compatibility & Warnings

To prevent chemical reactions that render nutrients unavailable to plants, observe the following compatibility constraints:

Do not mix with calcium-based fertilizers in concentrated solution to avoid calcium phosphate fallout.

Avoid applying in direct contact with seeds due to potential ammonia release injury.

5. Related Fertilizers

Compare or blend Diammonium Phosphate (DAP) with other high-grade fertilizer materials to complete your custom recipe: