Microbiome Interventions Combined with Artificial Humic Acid Treatments for Restoring Soil Bacterial Diversity

Abstract Soil health is under threat worldwide and technologies for the soil restoration are urgently needed. Here we study the effect of an artificial humic acids and soil microbiome transplants for the restoration of depleted soil microbiomes. We used a controlled microcosm experiment with gradients of microbial diversity, with and without A-HA, across three soil types. Microbial abundance, diversity, and composition were assessed using qPCR and 16S rRNA gene amplicon sequencing, complemented by metabolomic profiling of water-extractable compounds and growth characterization of bacterial isolates. A-HA treatment had a stronger effect on bacterial richness and community structure in degraded than in the original soil. Soil microbiome transplants were able to partially regenerate microbial abundances and increased bacterial richness and diversity in the degraded soils. Interestingly, the combination of A-HAs with addition of 10% soil transplants yielded the best restoration effect. The effect of individual as well as combined treatments was strongly depended on the composition of the native soil microbiome. From a mechanistic point of view, A-HA treatment inhibited fast-growing bacteria, which allow slow-growing bacteria to recover. By combined treatment, depending on the soil type and its native soil microbiome, we can synergistically restore the soil microbiome to resemble its original composition.