Manure on Hay Field

[JeffK-MN]

Hi I have 3 small hay fields one is 5 acres and the other 2 are 3 acres. They are about 3 years old. I have put fertilizer and lime on them but it was a old gravel pit that has most of the top soil gone.
I want to try and get it some better with manure spread on it.
But I have been told not to put it on till I'm done haying this year.
I have some old and some new manure. Some horse and some cow with old hay mixed in both.
When is it best to spread it on?
How much can I spread each year?
And still get good hay off it.
Thanks Jeff

 

[dun]

I pile it up as it accumulates then spread it in the late fall or early winter. That way it breaks down over the winter. As too how much, we spread whatever we have and put it on a different field/area each year.