March VIII: an audit of compost requirements…

Everyone is agreed that compost is good for your vegetable garden. Where people differ is in:

1. What they consider good raw materials for making compost.

2. How much compost you need to add per square metre of vegetable garden.

3. Whether it should be applied as a surface mulch or added at a deeper level.

As I use the no-dig method, I apply all my compost as a surface mulch.

With my 50sqm of growing space, my requirements are:

a. 5 cubic metres if I wish to apply a uniform 10cm covering to all beds;

b. 2 cubic metres if I wish to apply a uniform 4cm covering to all beds;

c. 55 pails, if I wish to apply 1 pail per square yard as was suggested in a 1940s publication of a prize winning gardener (of course, it might be helpful to define the volume of a pail, as no doubt different suppliers sell them in different sizes).

On a more pragmatic level, there is the issue of how much compost you can actually generate, rather than how much you would like to apply.

I have two ancient wire cages, which can realistically each be filled to contain about 0.5 cubic metres.

I also have four 0.22 cubic metre ‘daleks’, which can be used to finish compost in an environment protected from rain.

Given the fact that waste materials reduce in volume considerably, you need considerably more starting material than your final target volume of compost.

My approach is as follows:

1. I build a dedicated horse manure pile aimed at producing 0.2-0.4 cubic metres of compost to be applied in late November to the bed growing potatoes the following year.

2. I fill two wire cages in late March/early April when the first cut of grass produces a lot of green waste. I secure cardboard waste from garden centres and straw-based manure to act as brown waste. There is usually also some residue from previous piles which can act as a filler. I apply a few handfuls of volcanic rock dust as I build the layers.

These piles are usually ready to be combined at the summer solstice, at which point they are used as additives to the daleks each time sufficient kitchen waste is present  in those bins. During April, May and June, grass cuttings can be left to dry to become brown waste to add to daleks along with comfrey leaves, which accelerate composting beautifully.

As a result, careful management of the bins allows two rounds of composting a year in each dalek, which means around 1 cubic metre of high quality compost is generated from the daleks. I use this to treat the other 3 beds used in the four year rotation, although reality means that it is not all applied in November, rather when it becomes available/when new crops are being transplanted.

A third pile is built in a wire cage around the solstice and a fourth around the end of September. These also serve as ‘fuel’ for the daleks as well as lower grade compost for some of the boundary beds which are cultivated less intensively.

As I grow tomatoes in pots, I also end up with around 0.5 cubic metres of spent tomato compost, which is used where appropriate as compost.


In a perfect world, I would apply 5-7cm of compost uniformly across all beds. In the real world, I apply 4-5cm to my best growing areas and whatever else remains to the rest.


One thing is certain, if you compost all your garden materials rather than giving it each week to the council, you will be surprised how much compost you make yourself.

Author: Rhys

Rhys trained as a research biologist, working for a decade in the cancer research charity sector, before completing an MBA and working in management consultancy, technology transfer and early technology investment spaces, mostly working with UK academics to turn their scientific discoveries into value for society. AS a younger man, he was fascinated with mountains, both climbing them and ski-ing down them. Whilst living in Scotland, he completed a round of (then) all 277 Munros, the independent mountains over 3000ft originally complied as a list by Munro. He also spent his holidays representing the Ski Club of GB, as a Representative and Party Leader between 1990 and 1997. During that time, he found to his bemusement that he was able to predict, without understanding fully why, to a remarkable degree of accuracy, when good snow conditions would occur in the Alps, gaining an unworthy reputation for predictive genius in 1990 when predicting the evolution of the 1989/90 winter in Wengen, Switzerland for his CEO boss. He used this skill for the next seven years to ensure that he enjoyed powder snow pretty much every time he went ski-ing. An MD student he was training in Oxford also impressed his wife by taking Rhys' advice about when to take her to Italy in the mid 1990s! In recent years, Rhys has turned his mind toward how to grow prize tomatoes, winning several prizes in local and London shows and has, in the past 3 years, moved toward taking over a 50 square metre urban vegetable patch, which he has turned into a no-dig area since autumn 2014.

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