Investigating the effects of fish effluents as organic fertilisers on onion (Allium cepa) yield, soil nutrients, and soil microbiome

Le résumé fourni par la source

Although waste waters from aquaculture farms, known as fish effluents, have been shown to be a viable source of nutrients for crop production, their use is not permitted in organic production under the current European regulatory framework, Council Regulation (EU) 2018/848. In contrast, the use of livestock manure as fertiliser is allowed and indeed encouraged. In this work we tested the effects of two types of fish effluents – filtered and unfiltered fish waters – from an aquaponic system on the yield of onions (Allium cepa) and the soil nutrients and microbiome, compared with a fertilisation regime using composted horse manure. Soil fertility was enhanced by the addition of fish effluents, in particular in the soil treated with unfiltered fish water or sludge, which resulted in the soil with the highest nitrate content. Fertilisation with fish water and aerobically treated fish sludge resulted in higher yields than the manure, performing the best in all growth and yield measurements. The bulb weight and bulb diameter in the onions fertilised with manure were 102.43 g ± 7.26 and 61 mm ± 2.05 respectively, the ones fertilised with filtered fish effluents were 126 g ± 6.64 and 66.52 mm ± 2.17, and the ones fertilised with filtered (fish water) and unfiltered (sludge) fish effluents were 133.32 g ± 6.86 and 67.66 mm ± 1.81. The horse manure significantly affected the microbial community structure of the soil, resulting in a higher species diversity compared with the fish effluents, with the most predominant genus types being Flavobacterium, Pseudarthrobacter, Sphingomonas, Massilia, Nitrososphaera, Pseudomonas and Nocardioides. However, the microbial activity in the soil with fish effluents was also significant, which indicates that the soil treated in this way can be considered a ‘living soil’, as required for organic certification in the EU. Overall, the results confirm the findings of previous studies on the effectiveness of fish effluents as fertilisers, and highlight the superior performance of fish effluents compared with a livestock manure, thus directly questioning the prohibition on using fish effluents in organic agriculture.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.