NSW DPI's Sophie Parks sample nutrient solution for analysis.

Its desirable to prevent nitrate accumulation in vegetables, according to NSW DPI research horticulturist, Sophie Parks.

'From a human health perspective, vegetables with high levels of nitrate are of a poorer quality, for example containing reduced amounts of vitamin C, compared with vegetables having lower levels of nitrate,' she said.

'In terms of vegetable production it is also cost effective and environmentally responsible for growers to avoid excessive use of fertilisers supplying nitrate to growing plants. This reduces the risk of nitrate accumulation in plants,' she said.

Dr Parks said the aim of a Horticulture Australia project ‘Nitrates in vegetables on the Australian market’ which commenced in June last year was to assess the potential health benefits of Australian vegetables, in particular leafy vegetables, in terms of nitrate content.

'The effect of location, season, type of production system and post-harvest conditions on vegetable nitrate concentration is being investigated with the work expected to be completed by January 2008,' she said.

Dr Parks said the research included a regular survey of leafy vegetables sourced from Queensland, Victoria and NSW and a series of experiments investigating nitrate fertiliser supply, shading level and post-harvest conditions on plant nitrate concentration.

'Through this project determination of nitrate levels in Australian vegetables will reflect the quality of Australian vegetables and will identify any issues that can be addressed in production or post-harvest to further increase quality,' she said.

Dr Parks said nitrate could accumulate in vegetables for several reasons.

'Some plants are more likely than others to accumulate nitrate, such as the leafy vegetables lettuce and species from the Chenopodiaceae and Brassicaceae plant families, for example spinach and some Asian vegetables,' she said.

'Growing conditions are also important. High fertiliser inputs and low light levels encourage nitrate accumulation in plants.'

For example, Dr Parks said it has been shown in Europe that nitrates are high in lettuce and spinach grown in the short days and low light levels of winter.

'In Australia, we have high light intensities and so have the potential to produce high quality vegetables year-round using good agricultural practices,' she said.

Contact: Sophie Parks, Gosford, (02) 4348 1914.

This story appears in Agriculture Today.