I use a soil les growth medium referred to as MM
think of 15 buckets of stuff
Five buckets of five different composted materials, no two to be duplicates or bags with the some of the same materials if at all possible if your buying the stuff in as pre-bagged composted matter .
five buckets of coarse vermiculite
five buckets of peat or reconstituted coir waste
total number of buckets of soil less material is 15 buckets worth.
The different materials to use... One bucket of each to make a total of five buckets of composted matter
composted sea weed , composted fish waste , worm casts, bat guano composted cow muck with straw , composted horse muck with bedding's soaked in urine made up of straw , pulp wood or shavings or hemp waste . chicken muck with straw or neat , turkey muck with bedding's, goose muck ,composted or neat Llama beans , neat rabbit muck , composted pig muck , composted vegetable matter that has no soil in it but it can have torn up newspapers & corrugated brown cardboard , one bucket only of mushroom compost.
I didn't buy anything just used the animal dugurine 7 bedding's sourced locally and we composted them ourselves using " The Berkeley 18 day hot composting method "
Do not use stuff from the local amenity recycling place, it liable to have all manner of harmful stuff in it , like residual weed killers & other toxic chemicals , glass , sand , engine oil etc etc.
Only use one bucket of anything that has any form of wood product waste in it as the wood is not usually composted enough to allow it to produce nitrogen ..it steals it from the garden instead for up ti seven years or more.
Once I'd done my home composting and made up the growth medium I filled somewhere in the region of 9 cubic metres of raised beds with it and have grown some amazing crops .. Though for the first two years the long root veg did produce lots of massive forked roots
Right from the start I began making my own home made compost heaps with the Berkeley method and this has been used as replenishment nutrient to the bed ..I have no need to buy fertilizers anymore, but do use dried blood dried fish meal & dried ground up bone meal as an all in one top dressing feed for my onions.
The recipe :-
Five buckets of fluffed up peat or reconstituted fluffed up coir waste or fluffed up garden enhancer marketed in the name of VERVE from B&Q it's a mix of the two and from renewable sources apparently .
I got the compacted coir blocks of eBay in bulk with the enhancer chemicals in sachets included as I can always use them if needed in the future .
Five buckets of coarse to medium grade vermiculite .. comes in 110 litre bags that weight about 14 pounds each
I got mine from Keyline builders merchants & got 20 bags @ £ 21 ish inc vat this time last year . ( I still have six unopened ones left for making up my potting medium to the same formula for the next few years. )