Field Day on July 8, 2026, at the Frankenhausen Estate

Focus on Humus: Field Day Showcases Ways to Improve Soil Fertility

How can humus be specifically built up and maintained over the long term in organic farming? Answers to this question were provided at the field day“Focus on Humus – Soil Fertility in Organic Farming Put to the Test” on July 8 at the Hessian State Estate in Frankenhausen. Numerous farmers, consultants, and interested parties took the opportunity to discuss the latest research findings directly in the field.

To kick things off, Dr. Christopher Brock (Forschungsring Darmstadt) presented the latest findings on humus formation in organic and conventional agriculture. His message: Organic farming generally offers good conditions for humus formation, particularly through a high proportion of perennial forage legumes in crop rotations. However, the regular return of organic matter—for example, in the form of manure—remains crucial, while the intensity of tillage is less relevant. The subsequent panel discussion built on the presentation and addressed, among other things, the question of how humus content can be reliably measured and evaluated. It became clear that making reliable statements about humus content over larger areas is often difficult due to high site variability and methodological challenges. Nevertheless, soil analyses and long-term experiments provide important insights into the effects of various management systems and form a crucial foundation for the further development of agricultural practices.

In the afternoon, these findings were explored in greater depth on the experimental plots at the Frankenhausen Estate. The ÖLAF long-term experiment focused on strategies for humus accumulation on livestock-free organic farms. The results to date show that, in particular, fertilization with silage and the use of regionally available composts represent promising strategies for humus supply, even with only one year of cultivation of legume-grass mixtures. In the livestock-raising variants, a two-year clover-grass rotation shows a positive trend, which becomes even more pronounced with increasing stocking rates and the associated greater return of organic matter.

The TRIO project also demonstrated how perennial crops can contribute to climate adaptation. The deep-reaching roots of perennial fennel impressed many visitors. They build up humus, draw water from deeper soil layers, and leave behind stable biopores that benefit subsequent crops. At the same time, the flowering stands of fennel, cilantro, and caraway provided food and habitat for numerous insects. Thus, the studied mixed crops of perennial wheat, medicinal plants, and spice plants combine improved soil fertility with climate adaptation and biodiversity.

The KleeAss project presented various mixtures of legume-grass combinations and their effects on the subsequent wheat crop. Alfalfa in particular—whether planted alone or in combination with white clover—proved to be a high-yielding preceding crop for winter wheat, especially when it had been established early as an undersown crop in the previous winter wheat crop —these results underscored the importance of proper species selection and optimized management of legume-grass mixtures.

The demonstration on alternative minimum tillage in organic root crop cultivation also had practical applications. As a supplement to plowing, the soil was deeply loosened using a paragrubber before potato planting. Root profiles showed that potatoes had developed more vigorous and deeper root systems in the loosened areas.

In addition to the field stations, Naturland and the University of Göttingen provided information at booths about the reed glasswing cicada and the use of drones in wheat cultivation. The numerous questions and discussions at the stations demonstrated the visitors’ keen interest in practical solutions for maintaining soil fertility.

The professional exchange will continue this winter: As part of the Frankenhäuser Expert Discussions, two additional events on current topics in organic agriculture and crop production will take place on November 19 and December 10. The expert discussions bring together practitioners, consultants, and scientists, who will first provide brief insights from their respective perspectives. The focus then shifts to a joint exchange and discussion of the approaches and experiences presented. Further information on the program and registration will be published in a timely manner on the website of the Department of Organic Agriculture and Crop Production at the University of Kassel.