Plant biostimulants are diverse substances and microorganisms used to enhance plant growth. The global market for biostimulants is projected to increase 12 % per year and reach over $2,200 million by 2018. Despite the growing use of biostimulants in agriculture, many in the scientific community consider biostimulants to be lacking peer-reviewed scientific evaluation. This article describes the emerging definitions of biostimulants and reviews the literature on five categories of biostimulants: i. microbial inoculants, ii. humic acids, iii. fulvic acids, iv. protein hydrolysates and amino acids, and v. seaweed extracts. The large number of publications cited for each category of biostimulants demonstrates that there is growing scientific evidence supporting the use of biostimulants as agricultural inputs on diverse plant species. The cited literature also reveals some commonalities in plant responses to different biostimulants, such as increased root growth, enhanced nutrient uptake, and stress tolerance.

/pdf/agricultural-uses-of-plant-biostimulants-spbkauhybj.pdf

Agricultural uses of plant biostimulants

The burgeoning global market for soil microbial inoculants for use in agriculture is being driven by pressure to increase sustainable crop production by managing pests and diseases without environmental impacts. Microbial inoculants, based predominantly on bacteria and fungi, are applied to soil as alternatives to conventional inorganic fertilizers (biofertilizers) or to carry out specific functions including biocontrol of pests and diseases (biopesticides), or for bioremediation and enhancement of soil characteristics. While some soil inoculants such as rhizobia have a long and successful history of use, others have performed inconsistently in the field and failed to live up to their promise suggested by laboratory testing. A more precise understanding of the ecology and modes of action of inoculant strains is key to optimizing their efficacy and guiding their targeted use to situations where they address key limitations to crop production. This will require greater collaboration between science disciplines, including microbiology, plant and soil science, molecular biology and agronomy. Inoculants must be produced and formulated to ensure their effective establishment in the soil and practicality of implementation alongside existing cropping practices. New approaches to strain selection and construction of beneficial microbial consortia should lead to more efficacious inoculant products. Extensive and rigorous field evaluation of inoculants under a range of soil and environmental conditions has rarely been undertaken and is urgently needed to validate emerging inoculant products and underpin successful implementation by growers, especially in a market that is largely unregulated at present.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/sum.12811

Soil microbial inoculants for sustainable agriculture: Limitations and opportunities

The production and use of biologically derived soil additives is one of the fastest growing sectors of the fertilizer industry. These products have been shown to improve crop yields while at the same time reducing fertilizer inputs to and nutrient loss from cropland. The mechanisms driving the changes in primary productivity and soil processes are poorly understood and little is known about changes in secondary productivity associated with the use of microbial products. Here we investigate secondary metabolic responses to a biologically derived soil additive by monitoring changes in the phenlypropanoid (PP) pathway in Arabidopsis thaliana. This study was designed to test the influence of one of these products (Soil Builder™-AF, SB) on secondary metabolism after being applied at different times. One time (TI) application of SB to Arabidopsis increased the accumulation of flavonoids compared to multiple (TII) applications of the same products. Fourteen phenolic compounds including flavonols and anothocyanins were identified by mass spectrometry. Kaempferol-3,7-O-bis-α-L-rhamnoside and quercetin 3,7-dirhamnoside, the major compounds, increased 3-fold and 4-fold, respectively compared to control in the TI treatment. The most abundant anthocyanin was cyanidin 3-rhamnoglucoside, which increased 3-fold and 2-fold in TI compared to the control and TII, respectively. Simultaneously, the expression of genes coding for key enzymes in the PP pathway (phenylalanine ammonia lyase, cinnamate 4-hydroxylase, chalcone synthase, flavonoid-3′-O-hydroxylase, flavonol synthase1 and dihydroflavonol-4-reductase) and regulatory genes (production of anthocyanin pigment2, MYB12, MYB113, MYB114, EGL3, and TT8) were up-regulated in both treatments (TI and TII). Furthermore, application of TI and TII induced expression of the lignin pathway genes (hydroxyl cinamyl transferase, caffeyl-CoA O-methyl transferase, cinnamyl alcohol dehydrogenase, cinnamyl-CoA reductase, secondary wall-associated NAC domain protein1, MYB58 and MYB63 resulting in higher accumulation of lignin content compared to the control. These results indicate that the additions of microbially based soil additives have a perceptible influence on phenylpropanoid pathway gene regulation and its production of secondary metabolites. These findings open an avenue of research to investigate the mode of action of microbially-based soil additives which may assist in the sustainable production of food, feed, fuel and fiber.

/pdf/induced-transcriptional-profiling-of-phenylpropanoid-pathway-2ajmqeung9.pdf

Induced transcriptional profiling of phenylpropanoid pathway genes increased flavonoid and lignin content in Arabidopsis leaves in response to microbial products

Some members of the Bacillus velezensis (Bv) group (e.g., Bv FZB42T and AS3.43) were previously assigned grouping with B. subtilis and B. amyloliquefaciens, based on the fact that they shared a 99% DNA-DNA percentage phylogenetic similarity. However, hinging on current assessments of the pan-genomic reassignments, the differing phylogenomic characteristics of Bv from B. subtilis and B. amyloliquefaciens are now better understood. Within this re-grouping/reassignment, the various strains within the Bv share a close phylogenomic resemblance, and a number of these strains have received a lot of attention in recent years, due to their genomic robustness, and the growing evidence for their possible utilization in the agricultural industry for managing plant diseases. Only a few applications for their use medicinally/pharmaceutically, environmentally, and in the food industry have been reported, and this may be due to the fact that the majority of those strains investigated are those typically occurring in soil. Although the intracellular unique biomolecules of Bv strains have been revealed via in silico genome modeling and investigated using transcriptomics and proteomics, a further inquisition into the Bv metabolome using newer technologies such as metabolomics could elucidate additional applications of this economically relevant Bacillus species, beyond that of primarily the agricultural sector.

Bacillus velezensis: phylogeny, useful applications, and avenues for exploitation.

The present invention comprises compositions and methods for enhancing biological processes, such as plant growth or bioremediation. For example, the present invention comprises compositions and methods for effectively remediating chemical and organic wastes and reducing the environmental risk from manure, septic, sewage, oil pollution, and other contaminants.

Microbial compositions and methods

A method of modulating and in particular, reducing nitrous oxide emission from substrate for growing on or more plants by applying a microbial based soil additive and fertilizer blend to the substrate.

Method of reducing nitrous oxide emissions from a plant growth substrate

There is currently much interest in developing crop management practices that will decrease NO emissions from agricultural soils. Many different approaches are being investigated, but to date, no studies have been published on how microbial inoculants affect NO emissions. This study was conducted to test the hypothesis that microbial-based inoculants known to promote root growth and nutrient uptake can reduce NO emissions in the presence of N fertilizers under controlled conditions. Carbon dioxide and CH fluxes were also measured to evaluate microbial respiration and determine the aerobic and anaerobic conditions of the incubated soil. The microbial-based treatments investigated were SoilBuilder (SB), a metabolite extract of SoilBuilder (SBF), and a mixture of four strains of plant growth-promoting spp. Experiments included two different N fertilizer treatments, urea and urea-NHNO 32% N (UAN), and an unfertilized control. Emissions of NO and CO were determined from soil incubations and analyzed with gas chromatography. After 29 d of incubation, cumulative NO emissions were reduced 80% by SB and 44% by SBF in soils fertilized with UAN. Treatment with spp. significantly reduced NO production on Days 1 and 2 of the incubation in soils fertilized with UAN. In the unfertilized treatment, cumulative emissions of NO were significantly reduced 92% by SBF. Microbial-based treatments did not reduce NO emissions associated with urea application. Microbial-based treatments increased CO emissions from soils fertilized with UAN, suggesting a possible increase in microbial activity. Overall, the results demonstrated that microbial-based inoculants can reduce NO emissions associated with N fertilizer application, and this response varies with the type of microbial-based inoculant and fertilizer.

Microbial-Based Inoculants Impact Nitrous Oxide Emissions from an Incubated Soil Medium Containing Urea Fertilizers

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Method of reducing nitrous oxide emissions from a plant growth substrate

Microbial-Based Inoculants Impact Nitrous Oxide Emissions from an Incubated Soil Medium Containing Urea Fertilizers