Changes in use of nitrogen fertilizer are key to reducing greenhouse gases.
"2011's biggest problem will be food," John Beddington, the UK government's chief scientific adviser, told a meeting in London on 28 February.
Agriculture must become central to future climate-change discussions, he said, because it contributes a "significant" proportion of global carbon dioxide and nitrous oxide emissions.
The need to tackle climate change while producing more food to feed the world's growing population means that "climate-smart agriculture" is the only way forward, he told scientists, farmers and policy experts at the Royal Society, Britain's national academy of science.
Beddington says that the World Bank will attempt to push agriculture up world leaders' agendas when they meet at the end of the year to negotiate a climate deal at the seventeenth Conference of the Parties to the United Nations Framework Convention on Climate Change in Durban, South Africa.
Between 70% and 80% of agricultural greenhouse-gas emissions, such as nitrous oxide, come from the production and use of nitrogen fertilizers. So future rises in food production must be achieved without corresponding boosts in fertilizer use, added Gordon Conway, professor of international development at Imperial College London.
Conway heralded the 'fertilizer trees' Faidherbia albida as the future, particularly for farmers in Africa. These trees, which reintroduce nitrogen to the soil, have been shown to quadruple African maize yields in soils with no artificial fertilizer added.
But David Powlson, a retired soil scientist with a visiting professorship at the University of Reading, UK, urged caution. He says that countries' fertilizer use should differ according to their stages of development, particularly in Africa, which has soils that are starved of key nutrients such as nitrogen and phosphorus.
The overuse of nitrogen fertilizers elsewhere in the world, such as in China, "should not be used as an excuse not to give nitrogen fertilizers to Africa", he says.
Keith Goulding, a soil chemist at the agricultural research centre Rothamsted Research, in Harpenden, UK, and his colleagues are researching other methods of mitigating greenhouse-gas emissions from agriculture. "We are looking at ways of controlling the loss of nitrogen from the soil," he told the conference.
Goulding and his team are studying the soil microbes that convert nitrogen (from nitrogen-based fertilizers) into nitrous oxide, which is released into the atmosphere. In particular, they hope to manage the microbes, or their genes, so that less nitrogen is lost from the soil.
Preliminary results show that as nitrogen concentrations in the soil rise, there is a change in copy-number of some microbial genes that encode enzymes key to nitrogen escaping from soils. But in test soils with or without added fertilizer, there is little difference in which microbial genes are present, the researchers found. "The genes present are not necessarily the ones that are active," says Goulding. Researchers are now looking to identify the activity of these genes, not merely their presence or copy-number.
In a related experiment, they also found that soils release more nitrous oxide if they are dry and then suddenly become wet — a situation that may become more frequent with climate change. The researchers recommend that farmers keep soil moist to help keep nitrous oxide emissions down.
A group of thirteen scientists, including Beddington, began work last month to figure out how to achieve sustainable agriculture that contributes to food security, while tackling climate change. The scientists, who are working together as the Commission on Sustainable Agriculture and Climate Change, held their first meeting in Washington DC on 15 February. They will deliver their findings in a report to world leaders at the UNFCCC meeting at the end of the year in Durban.
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Gilbert, N. Climate-smart agriculture is needed. Nature (2011). https://doi.org/10.1038/news.2011.131