This is an important characteristic of liquid fertilizer solutions. The volume weight represents the weight in grams per cubic centimeter of fertilizer solution (gr/cm³). 1 gr/cm³ = 1 Kg/Lt = 1 metric ton/m³.
The volume weight of a 21% solution of Ammonium nitrate is 1.28 gr/cm³.
Therefore in 1000 cm³ (= 1 L) there are 1280 gr (1.280 Kg) of ammonium nitrate.
In 1 m³ (1000 litres) there are 1280 Kg (1.28 ton) of Ammonium nitrate.
The two most common means to determine the volume weight of a fertilizer solution are:
The hydrometer: an easy to use instrument, it is inmersed in the fertilizer solution and the volume weight is read directly on its scale in units of gr/cm³.
By laboratory analysis with three replicates: the average weight of 10 cm³ of the fertilizer solution determined on an exact scale.
Important!! It is very important to measure the volume weight of the solution in order to calculate fertilizer dosage. Solid fertilizers are sold and invoiced by weight. Therefore all commercial quantities are quoted in kilograms or in metric tons. Liquid fertilizer, however, are metered / applied by volume, (in litres per unit area). Therefore it is important to know the volume weight of each liquid fertilizer source.
A 32% solution of Urean (urea–ammonium–nitrate) contains 320 gr (pure) N per Kg of solution, as calculated with the following formula:
Weight of fertilizer x % nutrient concentration/100 = Weight of nutrient in one Kg fertilizer
1000 gr fert. x 32 % N / 100. = 320 gr N / 1 Kg fert.
The volume weight of Urean 32% is quoted as: 1.30 gr/cm³ (1.3Kg/L).
Therefore: 1 litre of fertilizer solution weight 1300 gr (1.3 Kg /Lt) and therefore contains 416 gr (pure) N as calculated with:
320 gr N / Kg fert. x 1.3 Kg/ L = 416 gr N / L fertilizer.
Important!! Wherever the volume weight of a fertilizer solution is mentioned in this catalogue, its always given in units of weight per cubic cm (gr/cm³), (Kg/Lt) or (metric ton/m³).
* Farmers, agronomists and fertilier distributors may also use the terms “density” or “specific weight”.