What is best for impoverished soil ?

Hello I use a company called kings compost he gets horse manure from racing stables then composts it for a couple of years it's well rotted and can be used for top dressing or as we do put it under the runner beans trench jezza

Any organic matter you can get your hands on...leaf mold, spent mushroom compost, spent hops from a local brewery, and obviously well rotted manure

I find mpc is good to start with but soon breaks down and loses structure so is not as useful as you might first think

And if you have space, perhaps start your own compost bins. I add masses of shredded paper to mine as well as everything else suitable I can get my hands on... serves me well, but not helpful to you right now Mrs B I know. But next year....

because adding organic matter is a regular job every single season

I've been looking at using green manures on a trial basis to see how green manures compares to other  manures  I found quite there was a write up on caliente mustard and the benefits of using this type of mustard including improving soil fertility

and because we have small holes in our potato crop that may be wireworm cliente mustard is said to deter wireworms and other soil-borne pathogens so its on my list to set out a plot for green manure trials

that's interesting to note jezza  thanks for that advise because I was intending to cut the mustard down by hand maybe its best to cut mustard on a dull day