CQU’s Professor David Midmore, based in Rockhampton, was invited to make a presentation to the Third OFA Conference, and the Darling Harbour Convention Centre, on the subject of sustainability in intensive organic production systems.

The conference was timed to coincide with the Organic Expo 2006, Australia's premier certified organic and environmental products and services (eco-ganics) expo.

Professor Midmore questioned the sustainability of nutrient management in organic production systems.

Focusing on vegetable crops, and arguing that organic manures release nitrogen at a rate that cannot easily be managed by growers, especially to ensure that it is only available at times when crops need high concentrations of soil nitrogen, he proposed a number of options to growers to reduce the loss of nitrogen and to increase the returns to added manures and composts.

These included ensuring a functioning root is always in the field (through relay cropping – the planting of one vegetable crop into an existing vegetable crop, before the latter is harvested), the use of simple starter solutions (a small quantity of concentrated nutrient solution applied to the root ball at transplanting), and the practice of ploughing in green-manure crops to ‘tie-up’ the readily available soil nitrogen.

He also spoke of the need to develop interrogative data bases that can predict release of available nutrients from ‘recipes’ of inputs used for the preparation of manures and composts.

The science and practice of these options are not well understood, and require substantial financial investment if the management of nitrogen in organic productions systems is to be considered sustainable.