engleski

Fertilizer performance of organic fertilizers as compared to synthetic fertilizer: a laboratory and a field scale assessment in Croatia

The European biogas and agricultural sector are currently not being developed at the same pace across the territory of the EU member states. While Western member states are creating a market for digestate and promoting its utilization in agriculture, the Eastern member states (e.g. Croatia) are still facing a lack of knowledge on chemical composition of digestate, absence of certification schemes on the national level and unclear legislative framework. To stimulate the development of biogas sector in the Eastern member states it is important to assess the fertilizer value of digestate and demonstrate to farmers that, next to the biogas production, digestate could also have a market value. Therefore, this study aims to i) assess availability and dynamics of nitrogen (N) mineralization in controlled conditions via laboratory incubation, and ii) determine the fertilizer performance of testing products in a full-scale maize production as compare to synthetic mineral fertilizer. Both experiments had eight different treatments consisting of solid and liquid fraction of digestate, NPK fertilizer (with top dressing of CAN), liquid cattle manure, a mix combination of digestate (solid and liquid) with NPK and control (i.e. unfertilized treatment). The field experiment was established in four repetitions, while the lab experiment in three repetitions during one growing season in Croatia. Results showed that the release of nitrogen highly depends on the material that was added to the soil while mineralization only occurred in bio-based materials that contained organic nitrogen. The value of nitrogen release, on average scale after 120 days of incubation experiment was in the order: synthetic mineral fertilizer > combinations of synthetic mineral fertilizer with solid and liquid fraction of digestate > liquid digestate > liquid cattle manure > liquid + solid digestate > control. Furthermore, results from field experiment showed that digestate had a similar effect on maize production as NPK fertilizer. The highest maize yield was observed in treatments with mineral fertilizer (NPK) and the combination of NPK with liquid digestate. The lowest crop yield was observed in the control treatment. Considering the fact that bio-fertilizers present an attractive and sustainable alternative to mineral fertilizers in Croatia, digestate showed a positive effect as a soil improver and will be further investigated.

digestate, bio-based fertilizers, nitrogen release, maize field experiment, nitrogen incubation

Acknowledgment The research is done as a part of the Systemic project that receives funding from the European Union’s Horizon 2020 Framework Programme for Research and Innovation under Grant Agreement no. 730400. See www.systemicproject.eu and www.biorefine.eu/projects/systemic for more information.