Aarhus Universitets segl

Converting soil with contrasting fertility and quality to semi-natural grassland: temporal changes in carbon storage and soil structural characteristics

Main subject area: Soil quality, Soil management, Soil recovery, Soil organic carbon, Soil structure, Pore characteristics

Short project description

Loss of soil organic carbon (SOC) is a major threat to sustained soil functions and services globally. Further, the climate crisis demands a focus on mitigating greenhouse gas emissions in agriculture. One strategy is to sequester CO2 from the atmosphere by converting arable land to grassland. However, it remains unknown how introduction of grassland will change the SOC storage and pore characteristics depending on the fertility and quality level of the arable land. The project exploits a unique long-term field experiment from Askov starting in 1981 with varying amounts of straw incorporation (0, 4, 8, 12 t/ha/year) and +/- ryegrass as cover crop in a spring barley monoculture. The experiment was terminated in spring 2020 and all plots were converted to semi-natural grassland. The plots hence had contrasting soil fertility and quality levels at the time when they were converted. The aim of this project is to quantify the temporal changes in SOC and soil structure for soils with different soil fertility and quality levels converted to grassland.

Department and supervisor

Project start

Any time

Physical location of project and students work

Department of Agroecology, AU Viborg

Extent and type of project

45 ECTS: Experimental theses in which the student is responsible for collection and analysis of his/her own original data or 60 ECTS: Experimental theses in which the student is responsible for planning, trial design and collection and analysis of his/her own original data.

Additional information

The project will build on data on SOC and pore characteristics measured in spring 2020 and autumn 2023, i.e. shortly before and 3½ years after the conversion to grassland. The student may supplement the dataset with bulk soil samples in the field experiment and carry out soil structural measurements such as soil structural stability and/or aggregate strength.

Useful reading

Chebet S, Munkholm LJ, Jensen JL. 2023. Rapid increase in soil organic carbon and structural stability in a sandy loam soil following conversion from long-term arable to semi-natural grassland irrespective of initial soil conditions. Geoderma, 438, 116646
Jensen JL, Eriksen J, Thomsen IK, Munkholm LJ, Christensen BT. 2022. Cereal straw incorporation and ryegrass cover crops: the path to equilibrium in soil carbon storage is short. European Journal of Soil Science, 73, 10.1111/ejss.13173.  Jensen JL, Schjønning P, Watts CW, Christensen BT, Munkholm LJ. 2020. Short-term changes in soil pore size distribution: Impact of land use. Soil and Tillage Research, 199, 104597.
Qi J, Jensen JL, Christensen BT, Munkholm LJ. 2022. Soil structural stability following decades of straw incorporation and use of ryegrass cover crops. Geoderma, 406, 115463.