Liquid fertilisers, both organic based and conventional NPK, have various benefits over their granular cousins. Firstly there is no granule pickup by the mowers or granules to disrupt the playing surface.
Secondly the application on a fairway or sports pitches can be much quicker and more accurate with a large sprayer than a granule applicator. Thirdly you can often combine treatments e.g. adding seaweed or other biostimulant to the tank thereby doing 2 jobs at once.