Liquid Fertilizer Density: UAN Solutions and Agricultural Spraying Guide
A complete guide to liquid fertilizer density for agronomists and spray operators. Convert kg to litres for UAN-28, UAN-32, ATS, and liquid NPK fertilizers.
The Importance of Liquid Fertilizer Density in Modern Agronomy
In precision farming, field spraying, and agricultural logistics, liquid fertilizers have largely replaced granular dry fertilizers for many intensive cropping systems. Commercial liquid nitrogen—most commonly Urea Ammonium Nitrate (UAN)—is delivered to farm holding tanks in bulk metric tonnes, priced per ton, but applied across fields through self-propelled crop sprayers calibrated in litres per hectare (L/ha) or gallons per acre (GPA).
A catastrophic mistake made by novice operators is treating liquid fertilizer as having the same density as water.
Commercial liquid fertilizers are concentrated salt solutions with densities ranging from 1.28 kg/L to over 1.48 kg/L—meaning a 1,000-litre IBC tote of liquid fertilizer weighs between 1,280 kg and 1,480 kg, nearly 30% to 50% heavier than pure water!
Ignoring fertilizer density leads to severe crop scorch, under- or over-fertilization, nozzle pressure miscalculations, and collapsed sprayer boom suspensions.
Density and Properties of Major Agricultural Liquid Fertilizers
The table below outlines standard densities, nutrient grades, and conversion factors for common liquid fertilizers at 15.5^°C (60^°F):
| Fertilizer Product | Nutrient Grade (N-P-K-S) | Density @ 15.5°C (kg/L) | Mass per 1,000 L (Tonnes) | Litres per 1,000 kg | Salt-Out Temp (°C) |
|---|---|---|---|---|---|
| UAN-28 | 28-0-0 | 1.280 | 1.280 t | 781 L | -18°C |
| UAN-30 | 30-0-0 | 1.305 | 1.305 t | 766 L | -10°C |
| UAN-32 | 32-0-0 | 1.325 | 1.325 t | 755 L | -2°C |
| Ammonium Polyphosphate (APP) | 10-34-0 | 1.405 | 1.405 t | 712 L | -18°C |
| Ammonium Thiosulfate (ATS) | 12-0-0-26S | 1.330 | 1.330 t | 752 L | -5°C |
| Potassium Thiosulfate (KTS) | 0-0-25-17S | 1.460 | 1.460 t | 685 L | -15°C |
| Liquid Potash Solution | 0-0-15 | 1.180 | 1.180 t | 847 L | -4°C |
| Anhydrous Ammonia (Liquid under pressure) | 82-0-0 | 0.618 | 0.618 t | 1,618 L | N/A |
Calibrating Sprayer Nozzles: The Specific Gravity Conversion Factor
All agricultural spray nozzle tip manufacturer charts (TeeJet, Hypro, Lechler) publish nozzle flow rate capacities in litres per minute of pure water (Specific Gravity = 1.00).
Because dense fertilizer solutions flow more slowly through a nozzle orifice at a given hydraulic pressure than pure water, operators must apply a Specific Gravity Conversion Factor (CF):
Conversion Factor = √(Fertilizer Density ÷ Water Density)
Nozzle Flow Calculation Example
An agronomist wants to apply 150 L/ha of UAN-32 (ρ = 1.325 kg/L, Specific Gravity = 1.325):
Conversion Factor = √1.325 = 1.151
Equivalent Water Application Rate = 150 L/ha × 1.151 = 172.65 L/ha
The sprayer computer must be calibrated using the equivalent water rate of 172.7 L/ha; otherwise, the sprayer will under-apply nitrogen by over 15%, robbing crops of critical yield potential at peak vegetative growth.
Calculating Active Nitrogen Application (kg N per Hectare)
To calculate how many kilograms of elemental nitrogen are being delivered per hectare:
kg N per Hectare = Application Rate (L/ha) × Density (kg/L) × % Nitrogen
Agronomic Field Example
A wheat grower applies 180 L/ha of UAN-28 (ρ = 1.280 kg/L, 28% N by weight):
- Calculate total liquid mass applied per hectare:
Mass = 180 L/ha × 1.280 kg/L = 230.4 kg/ha - Calculate elemental nitrogen delivered:
Active N = 230.4 kg/ha × 0.28 = 64.51 kg N/ha
If the grower had used water density (1.00 kg/L) in the calculation:
Underestimated N = 180 × 1.00 × 0.28 = 50.4 kg N/ha
They would erroneously believe they applied only 50.4 kg N/ha, leading them to over-apply additional fertilizer and cause severe crop lodging and nitrogen runoff into local waterways.
Essential Safety and Storage Rules for Liquid Fertilizers
- Tank Structural Load Capacity: Never fill a poly water storage tank with liquid fertilizer. Standard poly water tanks are designed for fluids with a specific gravity of 1.00. Filling them with UAN-32 (SG = 1.325) can cause catastrophic sidewall ruptures. Always use heavy-duty tanks rated for specific gravity 1.50 or higher.
- Salt-Out Temperature Awareness: Notice in our table that UAN-32 salts out (crystallizes into solid urea and ammonium nitrate crystals) at -2^°C (28^°F). In cold regions, farms should purchase UAN-28, which remains fully liquid down to -18^°C (-0.4^°F).
For rapid field lookups, use our dedicated liquid fertilizer kg to litres calculator.