Slow release granular fertiliser prodn. - by granulating a mixt. contg. alkaline earth (hydr)oxide and treating with carbon dioxide

Process for making long-lasting fertilisers comprises using lime, calcined dolomite and magnesite, cpds. of N,P,K useful as fertilisers and other usual components, by first granulating with addn. of water mixts. contg. >=30 wt. % alkaline earth oxides and/or hydroxides (calculated on oxides plus fertiliser ingredients). The granules are then treated with CO2 at 100-250 degrees C. Pref. the granules are granulated a second time, before CO2 treatment, with 5-20 wt. % alkaline earth oxides and/or hydroxides to give them an oxide coating. Treatment with CO2 causes partial recarbonisation of the surface oxides so that the speed at which the soluble fertiliser components are released is much reduced. Components which are normally incompatible can now be used together.