DPI staff Deirdre Harvey and Nerida Donovan, planting eggplants at the Centre for Recycled Organics in Agriculture at Camden.

A continuing trial at Camden is evaluating the benefits of using green waste compost for crop productivity and soil health in vegetable farming systems.

The field trial at the Centre for Recycled Organics in Agriculture (CROA) compares growing vegetables with compost against farmers’ conventional practices with a mixture of poultry manure and inorganic fertilisers.

The trial is being conducted under both high and low soil phosphorus regimes to see if compost can also play a role in reducing or reversing phosphorus accumulation in soils used for growing vegetables in the Sydney basin.

The first crop, broccoli, was planted in April and harvested in August 2005, said NSW DPI principal research scientist and project leader, Dr Yin Chan.

'Average broccoli yield was 12.9 tonnes per hectare; yield and quality using only compost was similar to yields achieved by conventional methods,' Dr Chan said.

'No yield differences were observed between broccoli grown in high and low phosphorus soils.'

In the next two and half years, a rotation of vegetable crops will be grown and monitored for yield and quality; DPI staff have just put in eggplants.

In addition, data on water consumption, chemical use and soil quality will be collected to perform a cost-benefit analysis and determine which management system during the three year project is the most cost effective forgrowers.

The source of the garden waste, which includes grass clippings and prunings for the trial, is close at hand - every year Sydney siders produce about a million tonnes.

From this, approximately 500 000 tonnes of recycled organic products, such as composted mulches and soil conditioners, are produced for landscaping and homegarden applications.

The products are high in organic matter and contain important plant nutrients such as nitrogen, potassium and phosphorus.

At present, only four percent of these materials are used in agriculture.

Six collaborative projects are currently underway at CROA, assessing new products derived from organic wastes, examining critical environmental criteria and indicators, producing best practice guidelines and developing extension programs for the sustainable use of recovered resources in agriculture.

Contact: Dr Yin Chan, Richmond on 02 4588 2108.

This story appears in Agriculture Today.