The secret life of the compost heap – a tale of muck and magic

There is an easy way to spot a diehard gardener, just ask them about their compost heap. This often-forgotten corner is the true ‘engine room’ of the garden, providing the valuable organic matter that is the key to improving soil health and fertility and the eventual success of the garden.

The compost heap is the meeting point of myth and science. Whilst the effectiveness of burying cows horns full of quartz is yet to be proven, the worth of composting is well recognised. The process of recycling organic matter from the garden back to the soil is an age old process, but has been elevated to an art form in modern times with hundreds of accessories for the compost buff, from tumblers and kits to build your heap, to 100s of additives to speed up the process. However you choose to do it, the partial break down of green waste to humus for use in the garden is now universally recognised as an essential and worthwhile process. Advocates who encouraged the modern composting renaissance include Rudolph Steiner, the founder of the Biodynamic system of farming, and Lady Eve Balfour, an early proponent of Organic gardening and one of the founders of the Soil Foundation. Their interest in mimicking the natural process of the environment signalled a move away from the industrialisation of agriculture and the dependence on chemical fertilisers to promote plant health.

Building a compost heap can be as complex, or as simple you want to make it. The first ingredient is organic matter. This should be broken down into suitably sized pieces, whether that means chopping it up in a shredder, or with a spade or loppers. The smaller the pieces, the larger the surface area for the bacteria and fungi to act on and the quicker the breakdown will occur. Compost heaps work best with a mix of materials. We need materials that are rich in Carbon. These will tend to be brown, and are often quite dry like woody prunings, leaves or even cardboard. We also need materials that are rich in Nitrogen. These will tend to be more colourful (often green) and could include grass clippings, veg peelings or bruised and rotting windfall fruit. We also need oxygen and water to feed the bacteria and we have our ideal mix. It is better to have higher carbon than nitrogen levels in the heap (20:1 is often recommended) as a heap high in nitrogen can sometimes stagnate, and begin to produce more methane and ammonia. Few of us will have the ability to monitor our carbon to nitrogen levels quite so accurately, so we must assume that we should just alternately add a little bit of both carbon rich and nitrogen rich materials at a time to ‘feed’ the heap.

Inside the heap the processes start to turn our waste into the most valuable of garden commodities, compost. Small earthworms like ‘Brandlings’, ‘Red wigglers’ and the ‘European nightcrawler’, who all specialise on fresh detritus, will start to colonise the heap. They perform a large part of the process, breaking the waste into smaller pieces, massively increasing the surface area and combining the different substrates together. This huge surface area is then colonised by many different bacteria, fungi, moulds and yeasts that will continue the digestion process, releasing the nutrients locked in the materials. These processes would also happen if the materials were left where they fell in the garden, but the high concentrations present in a compost heap will increase the speed of breakdown, and reduce the chance of these organisms causing problems on plants in the borders. 

The plants (and weeds) that thrive in our gardens do so because they are better than others at isolating, and accumulating the elements our soils may be deficient in. These plants are often termed ‘dynamic accumulators’ of these nutrients. By harvesting them (weeding) then composting and returning them to the soil we can take advantage of the high concentrations they contain to help rebalance and improve our soil.

By composting locally and returning it to the soil we ‘close-the-loop’, saving tons of carbon needed to move it to large-scale, industrial composting sites, then move it back to the garden when we need it to mulch the borders. 

At the garden I care for, when the council started to charge for the removal of household green waste, many of the local gardeners started to resort to bonfires to dispose of their waste. Now barely a day goes by when the air in the village isn’t filled with acrid smoke as one of our neighbours lights a bonfire. This waste of organic matter is completely unnecessary, an environmental hazard, and highly anti-social.

As any gardener knows, good gardening starts with a healthy soil, and the easiest way to improve your soil health is by composting. 


Author: jlrobbins

I grow plants

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