Laura Skadell

On June 16, 2025, Laura Skadell successfully defended her doctoral thesis entitled “Effects of agricultural management on organic carbon in topsoil and subsoil, and its implications for soil water retention” at Leibniz University Hannover. The dissertation was written as part of the BonaRes joint project Soil3 and supervised by Prof. Dr. Axel Don (Thünen AK) and Prof. Dr. Georg Guggenberger (Hannover). 

The project investigated how the water and nutrient resources in the subsoil (< 30 cm) can be better utilized for agricultural practice and how carbon dynamics behave in the soil profile down to a depth of 100 cm. Laura's task was to determine the extent to which agricultural management also affects organic carbon stocks in the subsoil. She also investigated how agricultural management affects the properties of organic soil matter, such as stable isotopes in topsoil and subsoil. She also analyzed the extent to which an increase in soil carbon through agricultural measures influences water retention capacity, especially plant-available water – a key aspect in terms of adapting agriculture to increased weather extremes. 

In her dissertation, Laura evaluated data from ten German long-term field experiments, with soil sampling reaching down to one meter depth. She was able to show that agricultural management influences soil organic carbon stocks down to a depth of 50 cm. In contrast, isotope contents changed almost exclusively in the topsoil. Here, fewer subsoil effects but complex relationships with the fertilization regime were observed. 

For the third part of her work, she used data from eleven field sites. The evaluations showed that even agricultural management with maximum increases in soil carbon content (e.g., long-term organic fertilization with manure) has only a minor impact on the soil’s capacity to store plant-available water. Therefore, other advantages of increasing soil carbon content, such as reducing soil erosion, should be given greater attention. 

The dissertation focused on the subsoil as an important nutrient-, water-, and carbon reservoir, thereby beginning to close important gaps in research.