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FertilCrop - investigating the significance of soil quality

In the Core Organic Plus project, FertilCrop, the focus is on weeds as indicators of changes in soil conditions. It is useful to know how certain management changes suppress or change the abundance of weeds.

2016.12.02 | Camilla Mathiesen

The tea bag technique can be used to demonstrate the pace of decomposition in different types of soil.

Andreas Fliessbach from FiBL, Switzerland is the Coordinator of the FertilCrop project. He presented some project activities at the Core Organic Research Seminar in Bucharest in October 2016.  

Andreas Fliessbach explains: "We found out, that a green manure crop is effectively suppressing weeds, but they appear again in the following crop, so we need more research into this.”

The project also uses a technique to look at weed seed decay. Project partners, who are running field trials on reduced soil tillage or green manure use, are placing litterbags filled with weed seeds in the soil in order to find out how many weeds are surviving over a certain time.

Farmer tools
The project aims at providing tools to farmers that allow them to follow the development of soil quality on their own. Most farmers know the spade test and they use it to determine if the soil is ready for primary tillage. The spade test, however, offers many other soil characteristics that the farmer observe and monitor. Soil structure and plough pans, anaerobic zones and porosity and in particular, the form and distribution of roots are indicating if there are problems in the soil profile. See the new video on this topic. All of the activities help to give a better picture of the role of the soil quality. Farmers and other experts are evaluating the acceptance and usefulness of the provided tools by the use of conceptual models and prototyping of optimal farming systems.

Citizens’ science approach
Commercially available tea in nylon bags is used to follow the decomposition in soils. This connects to a work package within the project that focuses on soil biology. The teabag approach can be seen as a mini litterbag technique. The teabags are buried in soils of field trials. They contain green tea and Rooibos tea that are decomposing at different pace in the soil. The green tea, which consists of young green leaves, decomposes quickly, and Rooibos tea decomposes slowly. Researchers developed this simple idea and build on a citizens’ science approach ( to draw a global map of decomposition.

Andreas Fliessbach explains: “The researchers want garden owners or farmers to apply this technique in order to learn about their soils but also take part in a global study, which is a great idea, since decomposition is an important ecosystem service.”

N dynamics
A part of the project relates to the dynamics of nitrogen, mainly focusing on the available literature. The researchers in this work package want to find out how to manage nitrogen in organic crop rotation in the best way. They also developed a technical note on how to use the number of nodules on the roots of leguminous plants to check nitrogen fixation. Simulation and prediction Other work packages in FertilCrop are simulating available datasets from field trials and once they found the appropriate parameters to simulate yield change or nitrous oxide emissions they can start predicting what may happen when soil management or the weather conditions are changing. This work will also result in the development of an applicable farmer tools to help in the decision making process on how much fertilizer the farmer has to apply in a given crop rotation.

Find more information on the FertilCrop project on



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