6.8 Use of organic streams to increase soil organic matter - Understanding soil biogeochemical responses

This position is closely related to Wetsus position 6.7.


Soils are a central element in the global ecosystem, linking water, food and energy flows. Soil erosion and declining soil fertility present a significant threat not only to food production, but also to fresh water quality and availability and carbon storage. Soil organic matter plays an important role in the build-up of healthy soil in terms of soil structure, biological activity, and retention of water and nutrients. In a circular economy, organic streams such as sewage sludge, animal manure and agricultural plant residues can be used to increase soil organic matter. Treatment of organic matter is required to reach appropriate biochemical conditions for soil application. More insight is needed to define the most suitable form of organic matter addition, required treatment concept of organic waste streams and the interactions between the organic matter and soil components with respect to micro-organisms, organic carbon, and nutrients/minerals.

Research challenge
The goal of this research project is to establish a platform to test end design residue (pre)treatment in order to achieve most optimal effects with respect to soil quality which conceptually will be approached by combining water treatment technology with soil biology and soil physico-chemistry.

Two main research directions (in two PhD projects) are:
6.7 Residue engineering: treatment of organic waste streams and effect of application of these amendments on soil physico-chemical properties;
6.8 Understanding soil biogeochemical responses: biogeochemical processes and interactions in soils in response to different additions of amendments.

Key questions are:
· What are the resulting physico-chemical properties of residues after (pre) treatment?
· What are the key physical, chemical and biological parameters influencing soil processes in relation to organic matter?
· What is the effect of treatment of organic waste streams (e.g. composting, anaerobic digestion, Bokashi treatment) on organic matter content in soils and on soil health?
· In what way does the increase in organic matter influence the run-off of nutrients and micropollutants?
· How do the microorganisms involved in the organic matter treatment influence the biochemical interactions in soil?
· What is the role of microbial additions such as Effective Micro-organisms (EM)/inocula in improving soil biological activity, with specific focus on biodiversity and crop disease control?

We are looking for two candidates with a MSc degree in environmental engineering, biotechnology, soil physico-chemistry, soil biology or similar discipline. Knowledge of soil microbiology is beneficial. Indicate in your motivation letter what is your main research interest: 6.7) residue engineering, or 6.8) soil biogeochemistry

The research project is part of the Wetsus research theme Soil. For collaboration in this project we have several interested companies and institutes who are involved in the management of organic streams, water bodies, and soil health.

Promotor: Cees Buisman (Wageningen University, Environmental Technology).
Co-promotor: Annemiek ter Heijne (Wageningen University, Environmental Technology).

For more information contact Inez Dinkla (

Wetsus, Leeuwarden, the Netherlands


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