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Case study 3: Germany: Crop diversification to improve water quality stability

Cluster 1: Service crops

In Lower Saxony, high stocking rates and economic pressure caused a simplification of cropping systems. As a result of this development, nitrogen levels in ground water rose thus giving rise to stricter fertilization laws. The area of Lower Saxony is characterized by a diversity of farming systems including specialized livestock production, specialized cropping systems and mixed farming systems. The challenge is to develop and introduce key changes in farmer practices to fulfil economic and nitrogen-use requirements in order to maintain stable farm incomes while reducing the environmental impacts.

What are the main problems underlying the emergence of the case study?

Widespread sandy soils and a historical specialisation in animal production has led to a high availability of organic fertilizers and simplified crop rotations, designed to match the requirements of animal production. The rapid development of biogas production from maize between 2002 and 2014 further enhanced this problem. Without the implementation of catch crops in the rotations, high levels of organic fertilization on sandy soils caused rising levels of nitrogen in ground water. With a diversity of farming systems in the area ranging from specialized livestock production to specialized cropping systems, in addition to mixed farming practices, countermeasures are difficult to implement. Stricter general fertilization laws coupled with harsh weather conditions are increasing problems further. 

How is the problem addressed and which actors are involved?

The challenge is to develop crop rotation sequences that can reduce the high risks of nitrogen-leaching associated with the current rotations. Therefore, data and experiences gained from the ongoing advisory in drinking water protection in Lower Saxony are used to develop suitable solutions on individual farms in the centre of Lower Saxony, around the regional office Nienburg of LWK Niedersachsen. While approaches of permanent green fields as a possible solution are not widespread in this area, a network of farms is set up to test single measures and adapt them to the current situation in the region. 

Solution investigated

With additional catch crops and undersown crops in the main crop as the most important measures, regional farms with existing experience in these practices are identified and grouped in a farm network. Instead of creating totally new approaches and solutions, the existing experiences are collected and evaluated to be published in a living manual for other farms. Since the availability of knowledge about such topics seems to be one of the main problems, this manual will give practical advice as well as provide contacts for farmers to get in touch with. Meanwhile, new approaches such as direct seeding and other plant-in-green methods are discussed in the network and will be tested in practice to give further recommendations and extend the manual over time.

Expected outcome

The collection and sharing of actual niche solutions and experiences on individual farms to a broader group of farmers, should lead to a wider adoption of the recommended measures. A more frequent use of catch crops, even over short periods, or the introduction of undersown crops will allow the farms to reduce mineral fertilization, through a more efficient use of organic fertilizers, and reduce nitrogen losses into ground water. The outlined changes in crop rotations may also be applicable in solutions for other problems such as stricter laws on pesticide use or more extreme weather conditions.

Relevance to the DiverIMPACTS goals

The case study will show that crop rotations can be altered and enlarge to increase water quality, as well as how to implement it in practice. The success here will be determined by the capability to solve issues regarding the economics of additional catch crops, and the evaluation of secondary benefits such as reduced greenhouse gas emissions or enhanced soil life.


  • Hauke Ahnemann, LWK Niedersachsen, case study leader
  • Dirk Ehlers, LWK Niedersachsen, case study monitor