How can the management of phosphorus (P) in organic farming be improved? Phosphorus (P) is essential for every living organism as part of its DNA and other molecules. Thus, it is also a vital ingredient of fertilizers. Nowadays, mined rock phosphate is often used besides farm manure. However, the finite rock phosphate would preferably be replaced by P fertilizers made from recycled waste material. FiBL, as a project partner of IMPROVE-P in the framework of the EU research programme CORE Organic II, is carrying out research to find possible solutions.
Within the framework of IMPROVE-P and under the coordination of Kurt Möller, University of Hohenheim (DE), the project members evaluated alternative recycled fertilizers in terms of their effectiveness, their risks, their energy needs and the acceptance in the organic sector. Additionally, they examined microbial and plant-based strategies to mobilise P from various P fertilizers. Sarah Symanczik and Paul Mäder of FiBL carried out field and pot trials. Additionally, an expert workshop on P recycling was organized at FiBL. Following the workshop, the experts and stakeholders were asked to fill in a questionnaire in order to assess how acceptable new P fertilizers made from waste products are in various countries. The results were published in the June edition of "Bioaktuell", the Swiss magazine of the organic movement.
Three fact sheets on the various types of recycled fertilizer have already been published. Currently, the fourth fact sheet on bio-ashes and chars is being prepared. The pros and cons of different recycled fertilizers are to be summarized. Since there is not a single recycled fertilizer with a very good rating in all categories, the first step will always be to assess which fertilizer is suited best for which situation. It is important that by closing the P cycles finite deposits are maintained and that many recycled fertilizers are less contaminated by heavy metals (e.g. cadmium) per unit P than rock phosphate.
In mid-May, the scientist participating in IMPROVE-P discussed the results of three years’ worth of research in Copenhagen. The consortium also visited the research station in Taastrup, Denmark, where since 2003, the effect of different recycled fertilizers on yields and soil quality has been examined in a field trial managed by Jakob Magid of the University of Copenhagen. In this trial, it has been shown that an increase in soil organic matter, after having applied compost regularly, reduces the fuel consumption during tillage. This aspect also needs to be considered when assessing the environmental impact of recycled fertilizer in the future.
Else Bünemann-König, FiBL Switzerland
- uni-hohenheim.de: IMPROVE-P Website
- orgprints.org: Bioaktuell article on recycled P fertilizer (in German)