I harrow my grass each spring when it's dry enough, usually end of March/April. I think it's essential to rake out the dead grass/moss etc and the one year I didn't do it the grass didn't grow as well. I also use it to spread the horse manure that has accumulated over winter! I get great satisfaction from flattening the molehills and it doesn't do a bad job of the trenches made by my rooting pigs, although it can't quite return the soil to a nice even consistency
.
Mine is a spring tine one with adjustable angle of the tines, so you can use it lightly or aggressively. The debris from the fields usually ends up stuck in the tines which I have to extricate into a pile after I've finished
.
This year I harrowed and rolled all the fields to perfection, and since the start of April it has done nothing but rain and my beautifully harrowed and rolled horse paddock is now a muddy quagmire with nothing left on it resembling grass
. I have to turn the horses back out onto the winter field (which I spent hours harrowing and rolling) and I'll have to start all over again when it's dry!!