An Organic Fertilizer 'Doped' with a Bacillus Strain Improves Melon and Pepper Yield, Modifying the Rhizosphere Microbiome with Negligible Changes in the Bulk Soil Microbiome

Doped compost consists of compost inoculated with Bacillus siamensis SCFB3-1 that is formulated in biochar and then mixed with the compost. The study objective was to analyze, at field scale, the effect of doped compost on the melon and pepper yield and on the soil microbiome, hypothesizing that the synergy between the components of doped compost confers additional benefits to the crop. Two doses of compost (2 and 5 t/ha) and two doses of the inoculant (biochar+SCFB3-1) with respect to the compost (3% and 6% w:w) were tested. The highest yield was observed for a reduced dose of mineral fertilization (NPK -20%) with a compost dose of 2 t/ha with 6% of the inoculant. Specifically, the yield increase compared with the control, which only received NPK, was a 47% increase in melon and 28% in pepper. The microbiome of the bulk soil was not modified by the doped compost, but the composition of the rhizosphere microbiome changed, increasing in the abundance of Bacillus (the inoculated strain), but also changing the relative abundance of other genera in the bacterial community. Future works will be focused on unravelling the possible effects of phytohormones on the observed results.

Automated summary

The study analyzed the effect of doped compost on melon and pepper yield and soil microbiome, and found that an appropriate amount of doped compost significantly increased crop yield. Specifically, using a reduced dose of mineral fertilization and 2 t/ha of doped compost resulted in a 47% increase in melon yield and a 28% increase in pepper yield.