Sunday, September 18, 2011

A lot of rot

I was working out in the garden on Sunday morning, getting the first of the spring flush of weeds out of the way of the daffodils, hyacinths and irises, and as I often do on Sunday morning, catching up with the National Radio programmes.  There was an interesting discussion about the costs of recycling, and the presenters briefly covered the amount of green waste that goes to the recycling centre.  In some councils’ case it amounts to about 50% of the waste stream, by volume.
New gardeners and perhaps quite a few of us “oldie” gardeners as well, have not realised the economic advantages of composting, quite aside from their advantages to the soil profile.
The activity of growing things uses up the humus in the soil, and depletes some of the soil’s fertility.  In the wild there is a never ending stream of humus and nutriment being returned to the soil in the form of leaf litter, but in our gardens that does not happen.  We harvest our crops – whether that be grass on the lawn, flowers in the house garden or vegetables in the kitchen garden – and often forget to return that goodness to the ground we are working with.
The chemical value of the nutriment, the nitrogen, phosphorous and potassium can be replenished by applying commercial fertilisers, but these products, useful though they are, do not restore the humus levels – to do that we need to return organic matter to the soil.  We can pay the recycling centre to do that, by paying to take it to the centre, and then later on, purchasing the processed compost (and I do that sometimes) but it is easier and more efficient to manufacture your own compost at home.  As well as improving the soil fertility and structure, compost aids the micro-biology of the soil, nourishing a wide variety of life from earthworms down to microscopic bacteria, and as it improves the structure of the soil it also aids in improving the soil’s ability to retain moisture, reducing the need to water so often.
I run a system with four plastic compost bins (a bit of an anachronism but there you go) as well as a large open-formed bin.  My large bin is built against a strong fence, with a buffer of chicken wire to stop leakage, and chicken wire fencing on the two sides.  The front is composed of slats which can be lifted, enabling me access to get in and dig out the compost when it is made.
When I start to fill one of the bins I like to put a layer of twiggy material at the bottom, to help provide the sharp drainage that is so necessary for the bins to work properly.  I always keep some of these when I am pruning in the garden, and have a little heap alongside the bins for when I start a new batch.
When you make your new brew it is important to keep a mixture of ‘greens’ and ‘browns’, the greens being types that are full of nitrogen while the browns tend are high in carbon and also tend to have more fibrous material.  The obvious ‘green’ is the weekly catcherful of lawn clippings but also includes kitchen food scraps, fruit peels, coffee grounds, tea bags, and chopped weeds.  Make sure not to include any of the bad weeds in your mix – you do not want to go spreading convolvulus or oxalis through the garden
‘Brown’ material includes straw, dried leaves and twigs, sawdust, wood shavings and wood ash (all from untreated sources) and  egg shells.  I like to have a few bales of pea straw around all the times, as they are the perfect ‘brown’ material, although by the time I get to use them they have started to rot down and almost become ‘green’!
Well-made compost is made from a mix of organic materials containing both 'green' and 'brown' materials, usually applied in layers of about 100 cm thickness.  I find I always have a steady stream of ‘green’, with clippings, garden waste and kitchen scraps, but the ‘brown’ stream is harder to reliably source, hence the straw bales.

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