Effects of the application of microbiologically activated bio-based fertilizers derived from manures on tomato plants and their rhizospheric communities

Bio-based fertilizers (BBFs) recovered from animal manure are promising products to optimiseresources recovery and generate high agricultural yields. However, their fertilization value maybe limited and it is necessary to enrich BBFs with microbial consortia to enhance their fertilizationvalue. Three specific microbial consortia were developed according to the characteristics of threedifferent BBFs produced from manure (bio-dried solid fraction, solid fraction of digestate and biochar)to enhance plant growth and product quality. A greenhouse pot experiment was carried out withtomato plants grown with microbiologically activated BBFs applied either as N-organic fertilizersor as an organic amendment. A next generation sequencing analysis was used to characterise thedevelopment of each rhizospheric community. All the activated BBFs gave enhanced tomato yields(fresh and dry weight) compared with the non-activated treatments and similar to, or higher than,chemical fertilization. Concerning the tomato fruits' organoleptic quality, lycopene and carotenoidsconcentrations were improved by biological activation. Metagenomic analysis points at Trichodermaas the main driver of the positive effects, with the effects of added bacteria being negligible or limitedat the early stages after fertilization. In the context of the circular economy, the activated BBFs couldbe used to replace synthetic fertilisers, reducing costs and environmental burdens and increasingproduction.