In the past, farmers used to smell their soil in order to ascertain whether their farmland was healthy. But an understanding of what is happening underground requires more than just a keen sense of smell. Radboud University ecologist Rosa Boone is focusing on an ‘electronic nose’ that can provide insight into soil conditions. In recent years, the growing demand for food has led to an intensification of the agricultural sector. Although this has boosted food production, which has been partly due to the use of fertilisers and pesticides, this intensification has also led to a reduction in underground biodiversity. Boone claims that this may be detrimental to soil sustainability. “When it comes to soil, it’s all about collaboration, including the collaboration between plants and soil life. Plants and fungi exchange sugars and nutrients. Once you add fertiliser, this collaboration is terminated. In addition to this, organisms work together to form a defence system against disease-causing fungi. And when there’s a decline in the biodiversity, the soil’s resistance to disease can also declines.” It is therefore crucial to know how “healthy” the soil is and how it functions, but this is not something that is easily ascertained. For a long time, farmers had to make use of their senses. This means that they had to rely on their experience and practical knowledge of the soil. It is now possible to take soil samples and analyse, for example the biodiversity by means of a DNA analysis. However, this method also has its drawbacks. “There’s a lot going on underground. Soil life is extremely heterogeneous and is constantly changing and samples only provide a static image,” says Boone. Measuring soil gases During her PhD research, Boone has been focusing on an instrument that can capture the dynamics of soil life and help farmers to monitor the condition of their soil. For this purpose, it is important to know what makes soil healthy. “Soil gases have the potential to become a proxy. During secondary metabolism, Microbes, fungi and bacteria emit gases in the soil. These are known as Volatile Organic Compounds (VOCs). Measuring these VOCs will give you a picture of the organisms that are living in the soil and, by extension, will possibly also provide you with a profile of the soil conditions.” A tailor-made product for farmers Different types of soils have a varying range of soil life. So far, Boone has collected VOCs from the sandy loam and clay soil in the Ooijpolder and VOCs from the sandy soil at Nijmegen’s Bodemzicht climate farm. “It’s for this reason that we’d like to assess whether there are any VOCs that are specific to different soil conditions. It would be perfect if you could link VOCs to specific groups of organisms in order to gain as detailed a picture of soil life as possible.” This would allow for the construction and comparison of VOC profiles. “As a result, we’d also be able to determine where the boundary lies between healthy and intensively used soil, and which organisms are associated with which types of soil management. It would be best if we could produce a tailor-made product that has been developed together with farmers. This could be a product like a sensor, which they could use on their farm in order to detect which soil gases are in their soil. This would allow them to monitor their own soil conditions and take any measures if necessary.” Living Lab Ooijpolder Rosa Boone’s PhD research is part of Living Lab Ooijpolder, which is a project in which scientists from multiple disciplines join forces with relevant parties such as farmers, authorities and companies in order to work on restoring the biodiversity and to focus on the key success factors for recovery. Photo: Dylan de Jonge via Unsplash