Feeding soils to feed a global population
Carbon lost to the atmosphere, from intensively farmed agricultural soils, is contributing to climate change. Professor Steve Banwart’s research is focused on developing farming methods that protect soils and enhance carbon storage while producing enough to feed a growing world population.
The key question driving Steve Banwart’s research is, “how can we use soil more intensively to grow enough food but do this in a way that does not contribute to climate change and environmental damage?” Soil is a vital part of the climate system, containing large amounts of organic matter and up to three times as much carbon as the atmosphere. Current intensive methods of land use for food production, forestry and biomass resource production all degrade soils, releasing carbon from the soils into the atmosphere as carbon dioxide. Soil organic matter is around 50% carbon, but also around 3% as the plant nutrient nitrogen that can be transformed by soil biota into nitrous oxide, a potent greenhouse gas.
“The key is getting more carbon and nitrogen into soils and keeping it there” says Professor Banwart. “This also has many important co-benefits, from improved water retention to better fertility through increased levels of phosphorus, nitrogen and other nutrients”. Through the CIRCASA project, working in partnership with over 20 mostly European organisations, the scientists aim is to create a ‘roadmap’ for the next 5-10 years of how Europe can encourage global action to improve soil management and land use for better carbon and nitrogen retention.
Research is showing practical actions that can make a difference. Disturbing the soil less, combats carbon that is lost through soil erosion, so reducing ploughing and using compressed air seed injection is one change in farming practice that could bring benefits. Methods familiar to organic gardeners, like mulching, adding compost and sowing green manures, are being trialled on larger scales, as ways to increase soil carbon and nitrogen in agricultural land. Using more perennial crop plants could be part of the solution, as these don’t need annual soil disturbance when sowing. A promising new practice pioneered by the Leverhulme Centre for Climate Change Mitigation is spreading silicate rock powder on agricultural fields, which draws CO2 out of the atmosphere and provides nutrients to crops as the minerals dissolve in soil.
Trees are particularly effective at capturing carbon and storing it as biomass, which increases soil organic matter over time. Agroforestry and interspersing crops with trees, are showing promise in cutting soil erosion and increasing soil carbon. The University of Leeds farm is a key resource in trialling new farming practices that could help us adapt to and mitigate the effects of climate change.
Soil’s building blocks are rock fragments, pore spaces filled with air and water, living organisms and decaying carbon from dead biomass. Fresh organic matter from plant litter and dead roots provides carbon and a source of energy for soil microbes to grow and these form biofilms on particle surfaces, pulling them together to form aggregates. These aggregates, or ‘crumb’ are the key to a good soil. Acting like sponges they allow the soil to hold more water within them giving drought resistance and also create larger pore spaces left behind as aggregates form, allowing for better drainage. They support the microbial activity which decomposes organic matter and releases the nutrients for plant growth.
“Understanding the development of soil from the underlying geology and how it creates the locally unique conditions for plant growth in different parts of the world, is key to solving the problems of food security in a changing climate.” said Professor Banwart. “We understand the aggregates in broad terms, but we can’t yet quantify all the effects or have the fundamental knowledge to understand all the linkages between organisms, water, air and rock in the soil system”. Understanding the fundamentals of soil and aggregate formation through mathematical modelling and soil chemistry and soil biology is one strand of his research. Valuable learning is coming from collaboration with other geochemistry experts, like Professor Caroline Peacock at the University of Leeds, who investigates organic matter and microbial interactions in marine sediments.
Understanding the development of soil... and how it creates the locally unique conditions for plant growth in different parts of the world is key.
In a joint project with China (Chinese Academy of Sciences, Nanjing University, and Jiangsu Academy of Agricultural Sciences) through the Newton Fund, the researchers are working to improve the sustainability of soils through getting organic matter back into soils using a circular economy approach. Taking organic farm waste and sewage sludge from cities to produce organic fertilizers for food crops is a way of recovering resources instead of producing waste, at the same time as bringing carbon and nutrients back into soils. This has the potential to be scaled up globally, reducing the demand for mineral nitrogen fertilizer, which currently carries large fossil fuel consumption and energy costs. Discussions with the regional and National governments in China are tackling the issues of what kind of policy interventions would be implemented to introduce this to farmers on a large scale.
Professor Banwart is the Director of the Global Food and Environment Institute (GFEI) at the University of Leeds, which is a major cross disciplinary research institute, bringing together expertise from across the university to solve the global challenges around future food security. This brings together engineers and biological scientists, working on the efficient manufacture of organic fertilizers, and climate scientists working on mitigation initiatives and crop adaptations to climate change. Researchers from the Law and Business schools bring expertise on adapting international trade for the circular economy, vital in helping assess the value of organic fertilizer products. “All these diverse disciplines are connected through GFEI, enabling us to build projects with the wide scope needed to find solutions to the global food challenges created by a changing climate” said Professor Banwart.
If you would like to know more about this area of research, please contact Professor Steve Banwart.