4 billion worth of nitrogen

By John Howieson

Associate Professor Howieson, Director of the Centre for Rhizobium Studies at Murdoch Unviersity in WA, in National Supervisor for the GRDC/AWI jointly funded National Rhizobium Program.

The nitrogen fixed by Australia"s pasture and pulse legumes has a national benefit worth about $4 billion a year. This estimate is based on data for nitrogen fixation rates, legume areas and the cost of urea fertiliser.

And the price of carbonbased fossil fuels is expected to increase substantially in the next five years, so the value of nitrogen fixation to Australian agriculture will further escalate.

It is also important to realise that more than 50 per cent of the nitrogen in cereals exported from Australia, and 85 per cent of the protein in meat and wool, derives from legume pasture nitrogen fixation.

In other words, of the six million tonnes of nitrogen required for crop and animal production each year, about 3.8 million tonnes is fixed by legumes. This equates to the nitrogen in eight million tonnes of urea.

However, without research supporting the rhizobiology of legumes, this asset is likely to decrease, and new species such as perennial herbaceous legumes may not reach commercial reality.

Nitrogen fixation benefits are not captured if legume nodulation is sub-optimal. This can happen in many ways:

Poor nodulation will also result from farmers not inoculating when they should, or from using inoculation practices that do not deliver sufficient rhizobia to the developing legume seedling.

It is the role of the National Rhizobium Program to ensure that Australian agriculture evolves with a reliance on legumes that are effectively nodulated. This reliance cannot be imported from Europe or the US, because Australia"s soils, environments, legumes and rhizobial strains are unique.

There is an imperative that we nurture the scientific infrastructure in Australia to protect and increase the $4 billion asset that exists in legume nitrogen fixation.

For more information: John Howieson, 08 9360 2231, J.Howieson@murdoch.edu.au