World Soil Day: Caring for the Planet Starts from the Ground and Nuclear Techniques can Help

Have you ever thought about soil? Thought about this vast limited resource where your food grows? This finite, non-renewable resource is under threat worldwide. Intensive agricultural practices, pollution and climate change threaten its health and the life-sustaining support it offers people and the planet.

But soil has an ally: nuclear science.

Nuclear science is a way to understand soil health and generate data to help improve its quality for food production, make it more resilient against climate change, and to protect it for the future. Scientists, with support from the IAEA and Food and Agriculture Organization of the United Nations (FAO), use nuclear and isotopic techniques to study what’s happening in soil. For example, they can estimate how quickly the soil is lost due to erosion by measuring caesium-137 radionuclides in soil. The data collected can help find ways to protect soil resources and develop guidance for sustainably using it. This work underscores the message of this year’s World Soil Day theme: caring for the planet starts with the ground.

Here are a few examples of the impact of using nuclear science for soil conservation in regions around the world.

Asia and the Pacific: Restoring soil health saves a Vietnamese coffee plantation

Dao Thanh Canh nearly lost his five-acre coffee farm in Viet Nam because his soil was no longer productive. Years of intensive farming and extreme weather became too much and caused the soil to start eroding. Watching it gradually disappear, Thanh Canh saw his livelihood and his family’s future slipping away.

“We were very worried as uncertainty loomed,” Thanh Canh said. “A few centimetres of the soil disappeared every year when we had big hail storms.”

Using fallout radionuclides and the compound-specific stable isotope technique (see The Science box), scientists were able to uncover the exact cause and source of the erosion and how quickly it was eroding. They put together a targeted conservation plan involving methods like intercropping, setting up water basins, and building terraces to hold the soil in place. As a result, they successfully reduced soil erosion by 45%. Now Thanh Canh’s soil is more stable, and his coffee plantation again profitable.

Thanh Canh’s story is just one of many from around the region. Scientists from China, Indonesia, Malaysia, Pakistan, Philippines, Sri Lanka, and Viet Nam have been working together to use nuclear science to help small-scale farmers combat soil erosion. Through their work to protect soil and reduce land degradation, they were able to identify effective soil conservation methods that reduced degradation in studied sites by 50%. This kind of information is used to guide farmers and land users in avoiding poor agricultural practices that can contribute to land degradation and instead adopt more sustainable methods.

Africa: Saving soil and preserving water resources in Morocco

Morocco’s steep, sloping land is losing fertile top soil. Erosion affects up to 40 percent of the country’s total land area. Harsh climate conditions and long periods of drought and short intense rain put a strain on the soil. When combined with overgrazing of animals, deforestation and poor planting techniques, this has led to soil losses of up to 100 million tonnes per year, much of which ends up clogging water reservoirs.

When this fertile top soil slides away, farmers lose a vital resource for growing food. This nutrient-rich resource ends up instead feeding algae in local water supplies, jeopardizing water quality and harming fish populations, said Moncef Benmansour, Head of the Division of Water, Soil and Climate at the National Centre for Nuclear Energy, Science and Techniques (CNESTEN). More than 75 million m3 of water storage capacity is lost each year in Morocco due to soil erosion. To stop the erosion we first needed to know exactly where the problems were, and that’s what isotopic techniques offered.

Through pilot studies using fallout radionuclides and the compound-specific stable isotope technique (see The Science box), scientists from CNESTEN and Morocco’s National Agronomy Research Institute (INRA) and the Forest Research Center (CRF) were able to pinpoint erosion-prone areas and evaluate the effectiveness of different conservation methods. Together with the farmers, they developed management practices involving non-tillage soil conservation techniques and planting cereal crops together with fruit trees and shrubs called Atriplex, which have a root system well-suited to holding soil in place. This reduced soil loss in the Tangier-Tetouan region by 40% and by around 60% in the Casablanca-Seta region.

Morocco’s experiences have also been shared with ten other African countries through IAEA technical cooperation projects and helped to improve research and soil conservation practices around the region.

Latin America: Protecting soil and greening Chile’s commercial forests

While it may be helping Chile’s national economy, intensification of commercial forestry can wreak havoc on the country’s soil. Large-scale forestry plantations, which cover about 2.5 million hectares of land, involve intense planting, logging and harvesting cycles and a constant flow of transport vehicles. These factors, combined with erratic weather, have contributed to a significant increase in erosion and deteriorated water quality.

Soil erosion is a silent process, and one of the biggest challenges is making people aware that when soil is lost, it is not a reversible process, said Claudio Bravo-Linares, professor at the Institute of Chemical Sciences at the Austral University of Chile. Since the government and the commercial forestry industry have seen that isotopic techniques work, we are continuously working with them to use these scientific results to determine critically degraded areas and efficiently mitigate the impact of soil erosion.

Using isotopic techniques (see The Science box), scientists in Chile found that one of the main sources of erosion in unharvested catchments was the unpaved roads used to move around the plantations and transport shipments in and out of the area. By implementing conservation methods, such as stabilizing forest roads with new layers of gravel and improving drainage capacity by repairing damage caused by moving heavy machinery, the forestry industry started to green the sector.

Now scientists in Chile are working together to use their research to provide the government ministries with data for effectively guiding commercial forestry companies toward more sustainable practices.


Fallout radionuclides and compound-specific stable isotope technique

Fallout radionuclides (FRNs) are environmental radionuclides that are found in the atmosphere and typically fall to the soil surface through rain. The three commonly used fallout radionuclides for soil erosion tracking are caesium-137, lead-210, and beryllium-7. These radionuclides are unique in how they bind to soil particles, which makes them useful for tracking and measuring the movement of soil. By analyzing FRNs using high-resolution gamma spectrometry, scientists can identify changes in soil redistribution patterns and rates in large catchment areas. They can also evaluate the efficiency of soil conservation measures in controlling soil erosion. Watch this animation to learn how cesium-137 has helped scientists study erosion.

The compound-specific stable isotope technique involves measuring stable isotopes like carbon-13 found in specific, soil-bound organic compounds, such as fatty acids, found in the soil. These fatty acids come from plant roots, animal waste and other remains found in natural ecosystems, which break down and become part of the soil’s organic matter. These compounds have certain unique stable isotope signatures, almost like fingerprints. By using the compound-specific stable isotope technique, scientists can match the ‘fingerprints’ of the compounds in the soil to those in ecosystems of the target areas. This can help them to identify where the eroded soil is coming from, which areas are prone to soil degradation, and how to effectively prioritize soil conservation needs.

Source: International Atomic Energy Agency