Effects of agricultural management on organic carbon in topsoil and subsoil, and its implications for soil water retention

authored by

Laura E. Skadell

supervised by

Georg Guggenberger

Abstract

Agricultural management can influence the soil organic carbon (SOC) stocks and the quality of soil organic matter (SOM). These in turn may have an influence on the water retention capacity of the soil. In order to make agricultural production more sustainable in the context of climate change, so that soils can continue to provide their ecosystem services (e.g. provision of clean water and food) in the future, an understanding of the relationship between SOM and soil water retention is required. Here, the subsoil (> 30 cm) is of crucial importance and at the same time the least understood. Within the scope of this dissertation, three studies were carried out in which the SOC supply (Study I), the SOM quality (Study II) and the water storage capacity (Study III) in the topsoil and subsoil (0-100 cm) were investigated. A total of 13 long-term field experiments, four short-term trials and three deep-ploughed soils were sampled throughout Germany. This thesis showed that the influence of agricultural management on the SOC stock is also significant in the subsoil. The SOM quality was particularly influenced by the agricultural management in the topsoil, as shown by the changes in the stable isotopes of carbon and nitrogen. However, detection of such changes was challenged in subsoils due to larger heterogeneity and overall lower SOM content. The water storage capacity of the soil, especially that available to plants, was positively, but only moderately influenced by higher SOC contents in the topsoil and subsoil. The results have implications for the accounting of carbon farming measures, as these generally only take into account changes in the topsoil and therefore ignore a significant proportion, namely 20 %, of the total management effect. Since a higher SOC content does not significantly contribute to a higher plant-available water capacity, the focus should be on other benefits, such as erosion control.

Organisation(s)

Soil Science Section

Type

Doctoral thesis

No. of pages

142

Publication date

21.07.2025

Publication status

Published

Sustainable Development Goals

SDG 2 - Zero Hunger, SDG 6 - Clean Water and Sanitation, SDG 13 - Climate Action

Electronic version(s)

https://doi.org/10.15488/19207 (Access: Open)