Sunday, 13 March 2011

The importance of compost

This is the start of an ongoing series of blogs on growing fruit and vegetables in your backyard. Last year I moved to a new property and decided to resurrect my vegetable garden to help reduce the weekly food bill.
Whilst the TV shows often glamorise growing in well manicured gardens, the reality can be quite different; yet a vege garden with a few weeds and the odd bug aren’t likely to change the flavour or appearance of your produce greatly, so don’t worry if you don’t have a lot of horticultural experience. The key thing is simply to get started. Like your fruit and vegetables, it all will grow from there.
In broad terms there are winter vegetables and summer vegetables. Winter veges like broccoli, cabbage and cauliflower are planted in late summer/ early autumn and summer veges such as tomato, capsicum, cucumber and sweetcorn are planted in spring, after frosts have finished and soil temperatures warmed.
Now that you have selected the type of vegetables that you wish to grow - in the appropriate time-slot, the next fundamental point is that the basis of a good garden, is healthy compost. If you lose the wheelie bin and start a compost heap you have already started to save money. The compost process involves converting the nutrients wrapped up in surplus growth such as plant prunings, weeds and household scraps into plant usable nutrients.

On a town section, space is limited, so the compost heap is best contained within a barrier. Alternatively purchase a commercially available compost bin. For ground based compost heaps like in the adjacent photo, ensure that it will be well drained. Avoid a location where stormwater run-off will wash into the mound. This is an example of a simple wooden bin, note that the front side can be lifted out for ease of filling/unfilling.

Start by placing larger coarse material such as sticks, prunings from shrubs or straw for the basal layer. To achieve good compost there should be air within the heap. It shouldn’t be a big soggy mess as many of the bacteria that break down the stalky plant material (cellulose) are aerobic. In addition for worms to colonise the heap, they too require oxygen.

Once the first layer is laid down, then apply a mix of grass clippings, food scraps and weeds from the garden in thin layers. Progressively build the heap alternating between the various types of plant material from around your garden.

In addition, leaf litter from deciduous trees or mulched prunings can also be incorporated into the heap. The key is to never put excessive quantities of dense material like lawn clippings in one layer, or it can create a barrier that won’t break down.  

Once your compost heap is prepared it will take up to six months to compost, depending on temperature. Summer temperatures being higher, accelerate the breakdown of the plant material. It may be necessary to water the heap in the first week or two, particularly if dry 'straw-like' grass is added. As we progress towards winter, temperatures cool and the compost process will take longer.
Mature compost contains key nutrients for plant growth such as nitrogen, potassium and phosphorus. Importantly it also contains digested organic matter to feed soil organisms like earthworms. Another benefit from your compost is many of the organic compounds from the digestion process act as 'glue' binding soil particles together, improving the soil structure in your vegetable garden and ultimately enhancing the yield potential of the soil.

Rich compost containing earthworms
In the short-term if you don't have compost, numerous commercially available composts are available at garden centres and horticultural supply stores.

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