Abstract
The use of biological inputs in crop production systems, as complements to synthetic inputs, is gaining popularity in the agricultural industry due to increasing consumer demand for more environmentally friendly agriculture. An approach to meeting this demand is the inoculation of field crops with beneficial microbes to promote plant growth and resistance to biotic and abiotic stresses. However, the scientific literature reports inconsistent results following applications of bio-inoculant to fields. The effects of inoculation with beneficial microbes on bulk soil and rhizospheric microbial communities is often overlooked as precise monitoring of soil microbial communities is difficult. The aim of this research was to use Illumina high throughput sequencing (HTS) to shed light on bulk soil and rhizospheric microbial community responses to two commercial microbial inoculants coated onto fertilizer granules, applied to potato fields. Bulk soil samples were collected 4 days before seeding (May 27th), 7 days after seeding (June 7th), at potato shoot emergence (June 21st) and at mid-flowering (July 26th). Rhizospheric soil was collected at the mid-flowering stage. The Illumina MiSeq HTS results indicated that the bulk soil microbial community composition, especially prokaryotes, changed significantly across potato growth stages. Microbial inoculation did not affect bulk soil or rhizospheric microbial communities sampled at the mid-flowering stage. However, a detailed analysis of the HTS results showed that bulk soil and rhizospheric microbial community richness and composition were different for the first treatment block compared to the other three blocks. The spatial heterogeneity of the soil microbial community between blocks of plots was associated with potato tuber yield changes, indicating links between crop productivity and soil microbial community composition. Understanding these links could help in production of high-quality microbial inoculants to promote potato productivity.
Highlights
In comparison to average food demand between 2005 and 2007, we will need to produce 60% more food by 2050 to meet the global demand (Alexandratos and Bruinsma, 2012)
We examined bulk soil and rhizospheric microbial communities of a potato field following the banded application at seeding of granular fertilizer coated with an EVL coating R (EVL) Coating R inoculum (EVL, St-Hyacinthe, QC, Canada) or an Éra Boost R inoculum (Ulysse Biotech, Trois-Rivière, QC, Canada)
We focused on two objectives by sampling bulk and rhizospheric soils: (1) to determine the impacts of granular fertilizer coated with a microbial inoculant on soil bacterial and fungal microbiomes and (2) to determine if the microbial species inoculated could be detected by high throughput sequencing (HTS) analysis in bulk or rhizospheric soils sampled at three time points following potato seeding
Summary
In comparison to average food demand between 2005 and 2007, we will need to produce 60% more food by 2050 to meet the global demand (Alexandratos and Bruinsma, 2012). A portion of these bioproducts are based on plant growth-promoting rhizobacteria (PGPR) These exogenous bacteria have beneficial effects on plant development and resilience to stress (Castro-Sowinski et al, 2007; Smith et al, 2017). PGPR can improve plant growth by interfering with other microbes in the rhizosphere Examples of these indirect benefits include the production of anti-microbial compounds or interference with microbial quorum sensing mechanisms (Pérez-Montaño et al, 2014; Nazari and Smith, 2020). Commercial inoculants can be of poor qualities with low quantity of viable propagules, leading to inconsistent results under field conditions (Herrmann and Lesueur, 2013; Gange and Gadhave, 2018) These microbial inoculants proliferate in the vicinity of plant roots and within them, allowing them to trade-off their beneficial effects by benefiting from root exudates
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