Biochar + AD exerts a biostimulant effect in the yield of horticultural crops and improves bacterial biodiversity and species richness in the rhizosphere

Abstract

[EN] Organic fertilisers are gaining prominence in advanced agri-systems due to the need for alternatives to the most pollutant agricultural inputs, contributing to sustainable agriculture. The objective of this study was to analyse the agronomic effect of a biochar non-additivated and additivated with anaerobic digestate (AD) on the soil microbiome in melon and pepper crops at the field scale, hypothesising that the synergy between biochar and the additive confers additional benefits to the crop. Two doses of biochar (250 and 500 kg ha−1) and two doses of additive with respect to biochar (5 and 10% v:w) were tested. The highest yield was observed for a reduced dose of mineral fertilisation (NPK −20%) with biochar + AD at the highest dose of additive: a biochar dose of 250 kg/ha with 10% AD for the melon crop and a biochar dose of 500 kg ha−1 with 10% AD for the pepper crop. Specifically, the yield increase compared with the control, which only received NPK, was a 33% increase in melon and 18% in pepper. The microbiome of the bulk soil was not modified by biochar + AD, but the composition of the rhizosphere microbiome changed, emerging plant growth-promoting rhizobacteria (PGPR) or increasing its relative abundance (e.g. Arthrobacter, Mitsuaria or Bacillus genus). We have demonstrated a positive correlation between yield and fruit quality parameters, and the presence of cluster of bacteria with predominance of known PGPR genera, that have been boosted by the treatments with biochar + AD. Thus, we hypothesize that the improved yield and fruit quality is in part due to the rhizosphere bacteria community enhancement.