Specific recruitment of soil bacteria and fungi decomposers following a biostimulant application increased crop residues mineralization

Abstract

Agriculture is undergoing important changes in order to meet sustainable soil management with respect to biodiversity (namely agroecology). Within this context, alternative solutions to mineral fertilizers such as agricultural biostimulants are thus promoted and being developed. The mechanisms by which some soil biostimulants sustain soil biological functioning and indirectly increase crop yields are still unknown. Our goal in the present study was to demonstrate if and to what extent the application of a soil biostimulant affects the soil heterotrophic microbial communities that are involved in organic matter decomposition and carbon mineralization. We hypothesized that the addition of a biostimulant results in changes in the composition and in the biomass of soil microbial communities. This in turn increases the mineralization of the organic matter derived from crop residues. We performed soil microcosm experiments with the addition of crop residues and a biostimulant, and we monitored the organic carbon (orgC) mineralization and the microbial biomass, along with the microbial community composition by sequencing 16S rRNA gene and ITS amplicons. The addition of a soil biostimulant caused a pH neutralizing effect and simultaneous enhancement of the orgC mineralization of crop residues (+ 400 μg orgC g-1 dry soil) and microbial biomass (+ 60 μg orgC g-1 dry soil) that were linked to changes in the soil microbial communities. Our findings suggest that the soil carbon mineralization enhancement in the presence of the biostimulant was supported by the specific recruitment of soil bacteria and fungi. Whereas archaea remained stable, several operational taxonomic units (OTUs) of indigenous soil bacteria and fungi were enriched and affiliated with known microbial decomposers such as Cytophagaceae, Phaselicystis sp., Verrucomicrobia, Pseudomonas sp., Ramicandelaber sp., and Mortierella sp., resulting in lower soil microbial richness and diversity.

Organic soil amendment with Spent Mushroom Substrate results in fungal colonisation, alters bacterial-fungal co-occurrence patterns and improves plant productivity

“…The lower microbial diversity observed in SMS treated soils at time zero is likely a result of an increase in dominant groups provided by SMS. The effects of the SMS community and nutrient inputs over the indigenous soil microbiota are observed in the early stages of the trial, as has been reported for other types of organic amendments (Hellequin et al, 2018). In this 100 day-experiment it was possible to observe a return of the prokaryotic community diversity to untreated soil-like levels, which did not occur in previously reported shorter term experiments using organic amendments (Hellequin et al, 2018).…”

“…Soil prokaryotic and fungal communities were significantly affected by SMS treatment at both DNA and RNA levels ( Figure 2 ; Table S3 ). The changes observed are likely to be a combined result of bioaugmentation and stimulation of specific microbial groups by the organic matter input (Hellequin et al, 2018). By contrast, the mineral treatment did not cause significant changes in fungal or prokaryotic community composition relative to the untreated soils.…”

“…The first stages of this process are carried out by fungi and bacteria capable of secreting hydrolytic enzymes, which break down complex carbohydrates (Berlemont, 2017). Thereafter, the course of the microbial community succession affects OM transformation (Fontaine et al, 2003) and, therefore, impacts nutrient availability (Hellequin et al, 2018).…”

Foliar Applications of Biostimulants Promote Growth, Yield and Fruit Quality of Strawberry Plants Grown under Nutrient Limitation

“…Moreover, B availability is generally decreased under higher soil pH [59]. Although the substrate pH at the end of the experiment was not measured, biostimulant applications could have slightly enhanced soil pH, therefore limiting B availability for the plants [39,60].…”

Responses of active soil microorganisms facing to a soil biostimulant input compared to plant legacy effects

“…In soil, biogeochemical cycles are partly regulated by saprophyte microorganisms that have an essential role in the decomposition and mineralization of soil organic matter releasing nutrients to plants 2,3 . Fitting with the agroecological principles is the use of biostimulants (BS) intended to select and stimulate beneficial soil microorganisms to indirectly sustain plant growth and productivity 5,6 . According to Yakhin et al 7 and Du Jardin 8 , biostimulants are defined as products of biological origin whose function, when applied to plants or soil, is to stimulate natural ecological processes in order to improve nutrient absorption and tolerance to abiotic stress in plants, and to increase the nutritional quality of plants, regardless of the nutrient content of the biostimulant.…”