Essential Guide to Successful Composting

Composting is the ultimate ‘soil formation’ tool for gardeners, resulting in rich and nutritious humus.  We get a lot of requests for compost accelerator at the nursery and whilst this is an actual product, you shouldn’t ever need to use it if you follow a few key steps when making your own home-grown gold!!!

An efficient composting system requires the right balance of carbon and nitrogen to feed the microbes that power the decomposition process.  The decomposition process is a natural process undertaken by soil microbes such as fungus and bacteria.  The correct ratio of carbon to nitrogen for a compost heap to decompose efficiently is 30:1 (30 times more carbon than nitrogen).  If you have too much carbon, nitrogen is quickly used up and the decay process slows.  If you have too much nitrogen, organisms snatch it up and then carbon is vented to the atmosphere or mixed with water and washed out of the heap.

Good sources of carbon provide the members of the soil food web (worms, nematodes, anthropods, bacteria, fungi etc) with energy for metabolism and the material to build their cells.  Nitrogen provides the soil food web organisms with the building blocks for proteins, which are used to build cellular structures and to produce the digestive enzymes necessary in the decay process.

Most of the materials you put into your compost heap will contain more carbon than nitrogen, however here’s a guide to assist you in getting your ideal ratio of 30:1.

Group A – Very High Carbon Low Nitrogen

Sawdust  N=0.11  C=450

Group B – High Carbon Low Nitrogen

Straw   N=0.5  C=100

Dead Leaves  N=0.7  C=70

Paper    N=0.27  C=170

Group C – Moderate Nitrogen Materials

Lawn Clippings/Weeds  N=2  C=20

Food Scraps  N=2.5  C= 15

Animal Manures N=2.3  C=20

Group D – High Nitrogen Materials

Blood & Bone  N=5  C=7

Feathers/Hair  N=10  C=4

Manure (grain fed) N=6  C=8

Other essential ingredients for a healthy and happy compost heap are oxygen and moisture.  There are two types of microbes, aerobic which need oxygen and anaerobic which don’t.  The anaerobic microbes are responsible for the unappealing odours in the compost heap and they also decompose organic material at a much slower rate.  So, in our compost heap we need to provide enough oxygen to ensure the aerobic microbes thrive.  Next is moisture, and most aerobic microbes require some moisture to prevent them from drying out, but if the compost heap is dry, the microbes won’t be happy and won’t decompose much material.  If the compost is too wet or soggy, there is very little space for air pockets as they’re taken up by water so the oxygen levels will be much lower resulting in the take over of anaerobic microbes and unhealthy, stinky compost.  As a rule, compost should be damp to touch but not leach water when squeezed

Turning compost is quite an important function for a number of reasons.  If compost isn’t turned regularly, the aerobic microbes we’ve been encouraging will eventually deplete the oxygen levels on the inside of the heap, so by turning the compost heap we introduce fresh air and oxygen for them to utilise.  Turning also brings less decomposed organic matter from the outer edges of the heap to the middle where all the main decomposition action is happening ensuring that all the material added to the compost heap is broken down.

Understanding your compost heaps needs will help you achieve healthy and happy humus for your garden.

If you need more information on composting, feel free to drop into the Sanctuary Point Garden Centre at 118 Macleans Point Road, Sanctuary Point and have a chat with Kathy.