Compost can be a rich resource for building up the fertility and productivity of our gardens.
Compost can be a rich resource for building up the fertility and productivity of our gardens. Photo: iStockPhoto

As the days become longer and the early signs of spring begin to appear, are we ready for the coming growing season?

Composting is the process of mixing a range of plant and animal materials together with a mixture of green and brown materials (nitrogen and carbon elements). With adequate moisture, the compost heap will generate internal heat of about 50C to 60C and decompose the organic materials in a similar way to how forests produce the deep litter. Beneficial fungi, bacteria, earthworms and other microorganisms all perform key roles in this transformation.

By producing our own compost, we are recycling lots of valuable natural resources and not just sending everything to landfill. In the natural environment, there is the recycling of nearly all animal and vegetable materials. Compost can be a very rich resource for building up the fertility and productivity of our own gardens.

There are ways of constructing quite ornate compost bins but one of the simplest methods is to build a compost heap directly onto the earth so that microorganisms can be quickly drawn into the decomposing materials. Earthworms can come up into the mound and then retreat back down into the soil when the temperature begins to rise.

The temperature will be hottest in the middle of the heap. Given that the surface area to overall volume of the heap will have an impact on heat retention, it is recommended that you set yourself the goal to create a heap of at least 1 cubic metre. A good internal temperature is important for killing off unwanted weed seeds and other pathogens.

Use materials that are small in size, if possible. We have been using a chipper mulching machine to chop up prunings and leaves trimmed off acacia windbreak trees, before adding them to the compost. Mowing long grass before adding it to the compost heap will also progress the decomposition process.

The optimum ratio of brown (carbon-rich) to green (nitrogen-rich) materials is about 30:1. Green materials such as lawn clippings and vegetable scraps are fresh and provide the heat to the compost process. Weeds, animal manures, blood and bone and other food scraps are nitrogen-intensive resources. However, too large a portion of soggy green materials will usually turn into a smelly mess in the short term.

Microorganisms have a diet that is much richer in carbon rather than nitrogen and the brown materials provide essential bulk to the heap. Dried grass stems, fallen leaves, old pea vines and straw are some alternatives. Mixing in some straw will aid the additional requirement of a compost heap - accessing air. Air will circulate more easily through the straw stalks, enabling aerobic bacteria to breathe freely, multiply more rapidly and conduct their essential business.

Turning your compost heap helps aerate the elements. You can also stimulate the decomposition process by adding each fortnight a small quantity of organic liquid fertilisers, high in nitrogen, such as the fish emulsions. Be patient - composting over winter will definitely take some months to produce the final product. In summer, with adequate moisture and regular turning of the heap, you might produce good compost within four months.

The finished product is like chocolate gold: a friable, rich, dark-brown crumbly material that can be dug back into your garden directly. It will have many, many living microorganisms which will continue to help plants access the range of essential nutrients.

>> Owen Pidgeon runs the Loriendale Organic Orchard, near Hall.

This week

■ Plant out onion and spinach seedlings. Sow lettuce seeds in punnets and locate in a warm sunny spot;

■ Apply a generous amount of compost as a top dressing to garden beds in preparation for spring plantings;

■ Aim to complete all winter pruning of apple, pear and quince trees (and roses) over the next week;

■ Apply one or two sprays of winter oil to citrus trees if there are signs of scale;

■ For stone fruit, apply one spray of Bordeaux mixture (or pre-mixed Kocide) at time of bud swell as a preventative against leaf curl in peaches and nectarines and shot-hole scab for apricots;

■ Ensure all support fences and trellises are secure and in good condition for the coming spring growth;

■ To make two litres of Bordeaux mixture, dissolve 20 grams of copper sulphate in hot water in a plastic bucket, then add two litres of cold water. Mix separately 20 grams of hydrated lime with a small quantity of water to make a paste. Add to the solutions and stir well.