Fewer fertilisers

Fertilisers are mixtures of chemicals that keep plants healthy. Without nutrients such as nitrogen and phosphorus, plants cannot grow or mature properly.

But manufacturing fertilisers requires huge amounts of energy, which is expensive and contributes to climate change. When it rains, the chemicals wash from fields into rivers and streams and can damage the ecosystem.

Can GM help? Giles Oldroyd, a plant expert at the John Innes Centre, thinks so. He is creating rice that can produce fertiliser from thin air...

Nitrogen fix

Plants need nitrogen to grow. But although nearly 80% of the air around us is nitrogen, most plants cannot use it. Instead, they use nitrogen-based chemicals in the soil, which farmers replace with fertilisers.

Some plants, such as clover and beans, can make their own fertiliser. Helpful bacteria living in lumpy 'nodules' on their roots take nitrogen from the air and 'fix' it into a form the plants can use.

'The problem is that most of our major crop plants such as rice, wheat and maize are unable to host nitrogen-fixing bacteria,' says Oldroyd.

Genetic N-gineering

Oldroyd is using genetic modification to help rice host these useful bacteria.

'If we can engineer our crop plants to work with nitrogen-fixing bacteria, then we will be much less dependent on nitrogen fertilisers,' he says.

'We are currently transferring the genes from clover into rice, trying to get rice to recognise the nitrogen-fixing bacteria. We do not know whether recognising the bacteria will be enough to get the partnership going, but it is the first step to transferring nitrogen fixation into these crop plants.'

Future hopes

Making crops that can use nitrogen from the air has long been the dream of crop scientists. Re-engineering the way plants work was thought to be an impossible task. Oldroyd's work has brought the goal much closer.

And the team won't stop there. 'Rice is an easy plant to do experiments on. However, if these rice experiments are successful then we plan to do the same with other crops such as wheat,' Oldroyd says.

'We hope this work will mean that farmers will no longer need nitrogen fertilisers.'

Phosphorus

Plants don't only need nitrogen to stay in tip-top condition. Fertilisers also contain phosphorus, which helps roots to grow.

Farmers used to use guano – bird poo – to top up their fields with phosphorus. Now we get the chemical from rocks, but there may only be 75 years of supply left, according to Peter Gregory, a crop expert at the Scottish Crop Research Institute (SCRI).

'Many places around the world, like Africa and Australia, face huge problems with soils containing low levels of phosphorus,' he says. 'This problem is becoming more widespread.'

Making the most of it

Scientists at the SCRI are working with the Australian Commonwealth Scientific and Industrial Research Organisation to help wheat thrive when phosphorus is low.

'We have made a new variety of wheat with an added gene from soil bacteria,' says Gregory. 'Its roots release an enzyme that helps it dissolve phosphorus, making it easier for the plant to absorb.'

The new wheat is already growing better than regular wheat in soils with low phosphorus. However, Gregory estimates it will be 10–15 years before we see grain with this characteristic in fields.