I will use commercial fert according to my test results mixed with a weed killer in the spring and normaly spread liter 2 more times during the year (pasture and hay fields) I can fert at a rate of 2 ton of liter per acre for only $20.00, at that price the return on the growth you get in your field makes it money well spent. I also rotate my cattle so they are never on a field right after I spread the liter, I want it to rain and wash into the grass before i put them on the field, I do the same with the liquid fert also.
The amount of times I fertilize is also driven by our rain fall or lack there of like it was this year.