making dung for composting.

White Clover wrote: »

You will still have a certain amount of p & k offtake go out the gate in the form of meat, milk etc. Stock don't make p & k.
Slurry/ dung from stock fed on forage grown on low index p&k ground is going to be low in p & k.
The straw will be a help in replacing some but where will the rest come from?

A bit of chemical p or k to maintain soil levels isn't the worst thing you could put out.
To get the most out of it with minimal effect on soil biology ideally you would know rough off takes in milk/liveweight versus bought in straw and meal.
Take regular tissue/soil samples to see what plants actually have available to them as well as what the soil sample says.
And from that aim to keep things stable with a topup of artificial fert. But it might not actually be needed as the soil testing system oversimplifies soils.
Also in the index system, 3 is to maximize yields. In index 2 the plant isn't deficient just it must divert more energy to the soil which means lower yields. But the soil gains, finding that balance that works best on you're farm is the challenge. Messing about leaving gaps with dung/fert (and maybe sample these) is probably the only way to find what suits you.
Cutting n and increasing sward diversity would do an awful lot on its own though even with normal p+k applications