Normal commercial nitrogen, phosphorous and potassium (NPK) solutions containing potassium are very dilute, containing not more than 12% K2O, because of the low solubility of KCl and K2SO4. The water content imposes an unnecessary load, in terms of volume of equipment and in expense, on storage and transportation costs.
The challenge for the fertiliser industry is to find NPK formulations which are as concentrated as possible (ie. using more soluble K salts) with minimum water, but remain liquid at the temperatures at which liquid fertilisers are normally transported.
Urea and ammonium nitrate (UAN) solutions are a step in the right direction for nitrogen-only solutions. UAN-type solutions would give maximum percentages of NPK and minimum expenses for storage and transportation both inland and overseas of liquid fertilisers. In practice, the producer would add 5-10% water as a safeguard against solid deposition during transport in unusually cold areas, and to keep the viscosity at...