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World Soil Day: Madagascar Combats Soil Erosion with Tradition and Nuclear Science

An age-old agricultural method is helping to combat soil degradation and protect a source of food and income for more than 75% of the population in Madagascar. Through a study using isotopic techniques on the mountainous island, scientists working with the IAEA, in cooperation with the Food and Agriculture Organization of the United Nations (FAO), found that traditional terrace farming can reduce soil erosion and run-off in the country by up to 40% when compared to unprotected agricultural fields.

“Farming on Madagascar is a challenge because there are a lot of steep, mountainous areas and high plateaus that limit the options on how to grow food,” said Lionel Mabit, a soil scientist at the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture. “Then when you add soil degradation and the impact of climate change, picking the right approaches to farming is essential. This project is helping them to implement optimal soil conservation strategies.”

Farmers rely on soil as an essential environment for growing food. Madagascar’s upland areas are particularly vulnerable to soil degradation due to challenging physical conditions, such as steep slopes and uneven ground that make soil more prone to eroding and running off. This is exacerbated by the effects of climate change like drought, floods and unpredictable rainfall that further break down soil structure and compromise its health. According to the FAO, around 30% of Madagascar’s land area is degraded.

The traditional method of farming in upland Madagascar is terrace farming. A terraced field is a series of raised flat areas, or steps, cut into the side of a sloping hill where farmers can grow their crops. These steps are formed out of soil and are often reinforced with stones or trees. Little channels are typically built into the steps to allow water to flow freely down the slope while holding the soil in place.

The "Lavaka", a typical erosional feature in Madagascar's highlands (Photo: Naivo Rabesiranana/INSTN–Madagascar)

Scientists at the Institut National des Sciences et Techniques Nucléaires (INSTN-Madagascar) in the capital Antananarivo worked with experts through the IAEA’s technical cooperation programme, and in partnership with the Joint FAO/IAEA Division, to use isotopic techniques to investigate and compare soil erosion rates in terraced and non-terraced agricultural fields. These highly-sensitive techniques allow scientists to track certain atoms, like caesium-137 and lead-210, in soil to determine the soil’s movement and its conditions. Watch this animation to see how this works.

“Although most farmers nowadays use modern intensive agriculture, terrace farming has been around for thousands of years,” Lionel Mabit said. “We know that this traditional method can reduce strain on soil and limit its redistribution. What this project set out to determine is exactly how well it does that in Madagascar.”

Their studies showed that traditional terracing systems significantly limited the loss of soil and reduced erosion by 40%, which means around three tonnes of soil are retained per hectare every year. Farmers in Madagascar are using the results of this study to develop sustainable soil conservation practices and better care for their fields, which ultimately allows them to grow more food.

“The results of this study should encourage farmers in Madagascar to revert to using traditional terracing systems to better conserve their soil,” Lionel Mabit said.

A worldwide issue

Madagascar is one example of how countries are increasingly using nuclear science to help them deal with soil degradation and loss — a major global problem remembered today through World Soil Day.

World Soil Day sets out to raise awareness of the important role of soil for all people. Soil is vital to food production, water supplies and climate regulation; though each year as much as 75 billion tonnes of fertile soil are lost globally due to soil degradation. This poses a major threat to the food security and livelihoods of billions of people worldwide.

The pressure on soil continues to increase as populations grow and along with it the demand for food and land. To help countries deal with this concern, the IAEA, in cooperation with the FAO, supports them in using nuclear science and technology to study and develop strategies to sustainably conserve and protect soil resources.

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