This. Very much thisI've always thought slurry spread onto chopped straw would be a good idea, and less risk of importing blackgrass etc.
Everything baled here though, most of it put through the pigs and back out as muck.
Ottomh there is about 7kg/t each of p&k, so roughly 3 quid of k & £4.50 of P. N is negligible, but lots of trace elements.
I charge my pig enterprise straw at what I could sell it at, (this year £55/t ex field) and sell the arable the muck at £8/t.
From an arable perspective, I count the om/soil conditioning element as equivalent to the cost of spreading the muck.
Muck is one thing that does more than it says on the tin - benefits last more than one season and it provides more than it's nutritional value.
Also seen more benefit from not ploughing it down, in spuds and cereals.
Is that the value of the available nutrients?