Assessing the efficiency and environmental impact of different bio-based fertilisers derived from fishery waste on broccoli under contrasted meteorological conditions - insight from an ecotron experiment

Abstract

Global climate change is recognised as the most significant threat to our ecosystems, biodiversity and human societies, and will particularly impact the agricultural sector and the way in which food is produced. To adapt to more challenging climatic conditions, reduce the negative impact of agriculture on the environment and to make more sustainable use of limited resources, new approaches to manage food production systems are urgently needed. In this context, bio-based fertilisation is a promising agronomic lever to address some of these changes in line with the circular economy model. This concept suggests the use ofbiological waste as a solution that recovers valuable fertiliser components and recycles nutrients, which can then partially or completely replace chemical fertilisers. This Master's thesis is part ofthe European SEA2LAND project, which aims to produce different innovative bio-based fertilisers derived from by-products ofthe fisheries industry ofthe major European Seas, and assess their effectiveness and environmental impact in agronomic trial studies. Here, the performance of four selected bio-based fertilisers was assessed under two contrasting climatic conditions simulated in the Ecotron facility at Gembloux Agro-Bio Tech, University of Liège. Complementing previous field trials conducted in the framework of this project, the model plant for this study was broccoli (Brassica oleracea L. var. italica Plenck), a universal and popular crop across Europe. The first climate scenario realised in the Ecotron consisted of conditions conducive to broccoli cultivation, used a reference for the present climate; and the second scenario simulated a future climate based on the Representative Concentration Pathway (RCP) 8.5, taking us to the year 2095. The broccoli plants in the Ecotron were cultivated in intact soil monoliths from an agronomic field to be as representative of field conditions as possible. The replicate plants in the Ecotron were then treated with either one of the different bio-based fertilisers, a commercial control fertiliser, or remained unfertilised as negative control. Several measurements were taken throughout the growth cycle of the plants to monitor their performance, notably using different leafsensors and image analysis. In addition, measurements to quantify the impact of fertilisers on the wider ecosystem including soil and atmosphere were performed, including quantification ofoverall enzyme activity in the soil and greenhouse gas emissions. At harvest, the fresh weights ofthe various plant organs and the diameter ofthe heads were also measured to investigate biomass partitioning and the commercial quality ofthe marketable broccoli parts. Most crop performance and environmental parameters showed contrasting results between the two climate scenarios, with overall reduced plant growth in the future climate and mostly higher soil activity and higher greenhouse gas emissions in the present reference climate. Comparing the different bio-based fertilisers to the commercial control revealed some competitive potential of the bio-based fertilisers, which could enable a successful and sustainable production of this crop in the future. However, in particular nitrous oxide emissions were significantly enhanced for some bio-based fertilisers, which highlights the need for future studies investigating the influence of organic fertilisers on soil microbial activity and ecological feedbacks in more detail.