I garden on around 50sqm of no-dig beds plus some paths, which I cover in spring with the waste generated during passage of ‘compost’ through a coarse sieve.
My strategy at the moment is:
1. Visit a local stables in the early autumn and do about 4 runs in the car with 4 ‘green waste bags’ supplied by the council and a spade, to create a heap of horse manure + straw which rots down over the next 12 months, creating enough to treat the bed for potatoes the following spring, the dedicated pea stretch and the small cherry, plum and pear trees.
2. Generate 0.5 – 1.0 cubic metres of homegrown compost, through a combination of building 0.8*0.8*0.8m heaps in a oner in April time, using fresh horse manure, grass cuttings, newspaper, cardboard (from the waste of a local garden centre), leaves, turning them several weeks later and then transferring this into green bins, where subsequent additions of comfrey, kitchen waste, green waste from harvested crops etc etc is incorporated, along with twigs and small branches (which never fully rot down but are repeatedly returned to compost heaps to help with humus creation). These are topped up repeatedly until about October when they are left to rot down over winter to be ready for use in the spring as needed. The second big heap generated is transferred to other green bins in September and those are topped up through the winter with food waste and then left from March onwards to mature for use in where late summer/early autumn plantings take place.
These first two sources cost only the petrol for collecting the horse manure – probably no more than £15 a year plus whatever you charge to the car depreciation for 60 – 70 miles (probably another £25 – 35).
3. The soil/compost used for growing tomatoes/potatoes in pots is kept in the bags the compost was bought in over the winter and used on salad beds. This is costed not in no-dig calculations but rather in the cost of growing tomatoes or potatoes in pots!
4. This year, I am experimenting with a leaf covering of the bed to be used for parsnip, onion and carrot after a successful small-scale trial in 2015. This of course costs nothing.
I’ve looked at the cost of buying ‘commercial’ manure and its £70/tonne around here. However, if you had a 250sqm allotment, you can get a ‘lorry load’ from a local farmer for under £50, which sounds far cheaper (as it will be several tonnes delivered to the allotment site).
My calculations say if you cover the whole garden with ‘compost’ I need around 1.25 – 1.5 cubic metres per year.
Using the various sources I describe, it all costs in at around £100, of which about half is the cost of compost used to grow tomatoes and potatoes in pots (I do grow rather a lot of tomatoes outdoors – around 100lb a season on around 20 plants). The rest is the petrol plus depreciation costs for collecting all the manure.
I will be most interested in what the outcomes of leaf mulch trials will be, as I can source enough fallen leaves within 200 yards of the garden to cover all the beds easily. The only problem is when you have storms like this weeks’ ones and a whole bed of leaves end up on the garden grass again! I guess there may be a case of putting protective sheeting over the leaves and weighing down with bricks etc.
I’m also going to acquire a wood chipper soon and try a little experiment placing wood chip as a ‘permanent mulch’ to see it the stories on the web about this being a ‘magic top dressing fertiliser’ have any substance or not (since neighbours have sufficient large trees which are cut regularly to provide a sufficient source for many beds if such an approach has real benefits in real trials).