Making fertiliser out of thin air will revolutionise agriculture

Plants that breathe nitrogen. University of Nottingham

Each year more than 1 million tonnes of mineral nitrogen fertiliser is applied to arable and grass crops in the UK. This pollutes waterways through nitrate run-off and the atmosphere from the release of ammonia and nitrogen oxides.

Nitrate pollution represents a significant health hazard and causes oxygen depleted “dead zones” in our waterways and oceans. A recent study estimates that the annual cost of damage caused by nitrogen pollution across Europe is £60-£280 billion a year.

The world needs to unhook itself from the Haber-Bosch process of nitrogen fertiliser production. The energy, economic and environmental costs are too high. With global concerns about food security, sustainable production, and consumer worries about GMOs, an alternative is desperately required to enable more effective delivery of nitrogen.

The development of a seed inoculation based upon a naturally occurring bacterium called Gluconacetobacter diazotrophicus (Gd), which is able to remove nitrogen from the atmosphere, offers a genuine opportunity to deliver such a solution. The inoculation and the symbiotic relationship of crops such as peas and beans with a nitrogen-fixing bacteria called Rhizobia has long been known and promoted in agriculture. These bacteria are applied to seeds or the soil where they are taken up by the growing plant in their root nodules, where they fix the nitrogen.

The ability of such legumes to produce root nodules is essential to this relationship. Research is underway by other organisations to genetically modify crops to enable them to produce root nodules, but we are many years away from developing a practical solution.

However, we have discovered that under certain conditions Gd - a bacteria originally isolated from sugarcane - will colonise growing cells of the developing root of any crop plant, where it then fixes nitrogen. This means a practical solution to help reduce nitrogen fertiliser use by farmers will be available within a few years.

The approach is neither genetic modification nor bio-engineering. Rather, we used simple but effective means to encourage this naturally occurring bacteria to form a symbiotic, mutually beneficial relationship with the plant. The plant provides sugar used by the bacteria as an energy source in order to fix nitrogen, half of which is released to the plant for protein production and growth.

Through staining the bacteria and using microscopic techniques, it was possible to see the Gd within plant cells. Unlike Rhizobia, which is confined to the root nodules of peas and beans, the Gd moves throughout the whole of the plant, the roots, stems and leaves.

This research has taken more than 10 years, with extensive programmes on a range of crops in the laboratory, growth rooms and glasshouses.

It has been possible for plants to be grown in the laboratory in the total absence of any fixed nitrogen within their roots so that they have to fix nitrogen from the air around them. This is the ultimate demonstration of the bacteria functioning in true symbiosis with the plant.

However, it is not an expectation or even necessary that the bacteria produce all of a plants’ nitrogen requirements. Rather, it should be sufficiently effective to allow the reduction in use of synthetic nitrogen fertilisers. This alone will provide a cost saving to the farmer while maintaining or even increasing yields. It would also reduce the scale of the negative side effects of water and atmospheric pollution from nitrogen fertilisers.

The current research programme has moved into a product development phase via Azotic Technologies Ltd in order to determine how well the Gd inoculation works under normal crop growing conditions. Initial results are promising and it is anticipated that within two years, products based on Gd will be available for farmers, for use on a wide range of crops, on a global basis.

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