Production Of Humic Acids Research Articles

Study on stabilization of mercury in wastewater and soil by modified coal-based humic acid residue.

Coal-based humic acid residue (HAS), as a waste generated during humic acid production, has been gaining attention in recent years due to its adsorption capacity and containing nutrients. In this study, to improve the adsorption capacity of HAS for and Hg, phosphate-modified materials (N-HAS) were prepared by a hydrothermal method and HAS and N-HAS were characterized by scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), X-ray fluorescence (XRF); batch adsorption experiments investigated the adsorption capacity of N-HAS on Hg2+ under different pH, and isothermal adsorption model and kinetic model fitted the adsorption process to explore the adsorption mechanism; the effects of various amounts of N-HAS on the Hg content in maize and the effective Hg in the soil under Hg-contaminated soil were investigated by field trial. The results showed that the pseudo-second-order kinetic model (R2=0.9641) and Langmuir isothermal (R2=0.95) adsorption model could better describe the adsorption behavior of N-HAR on Hg2+, the maximum adsorption amount was 124.20 mg/g, and the time to reach adsorption equilibrium was shorter for N-HAS compared to HAS; after 5 times of adsorption-desorption, the removal rate of Hg2+ by N-HAS was still higher than 80%, with stable cyclic adsorption performance; the adsorption mechanism of Hg2+ by N-HAS included physical adsorption, precipitation, and surface complexation, and compared with HAS, the percentage of complexation for Hg2+ adsorption by N-HAS increased by 77.81%, and the percentage of precipitation increased by 7.68%; compared to the control group, it was shown that the addition of N-HAS significantly decreased (p < 0.05) the Hg content of maize kernels by 27.44% ∼ 72.09%, increased biomass by 4.34% ∼ 11.26%, and decreased the available Hg content in soil by 50.00% ∼ 82.80%. In addition, the addition of N-HAS at 0.4 kg/m2 was optimal for the field trial. The study showed that N-HAS not only achieved resource utilization but also demonstrated great potential for treating Hg2+ in water and soil.

Effect of Lignite Addition on the Production of Biochemical Humic Acid in Sheep Manure

Effect of Lignite Addition on the Production of Biochemical Humic Acid in Sheep Manure

A sustainable approach to enhancing humic acid production from lignocellulose via green alum

A sustainable approach to enhancing humic acid production from lignocellulose via green alum

Effect of peroxydisulfate activated by B-doped NiFe2Ox for degrading contaminants and mitigating nanofiltration membrane fouling in the landfill leachate treatment

Catalytic oxidation pretreatment is a significant focus in the field of membrane fouling control; however, traditional catalytic materials are plagued by limitations in catalytic sites and challenges in recovery. In this study, a novel catalyst, B-doped NiFe2Ox, was prepared with magnetic recovery capabilities and abundant oxygen vacancies to address landfill leachate treatment and mitigate membrane fouling. The results demonstrated the efficient activation of persulfate (PS) by the catalytic sites on B-NiFe2Ox, which significantly degraded the complex organic pollutants like conjugated double bonds and aromatic compounds in landfill leachate. A large amount of humic acid and soluble microbial products in the landfill leachate were efficiently degraded upon contact with sulfate and hydroxyl radicals produced by B-NiFe2Ox/PS, thereby resulting in achieving a chemical oxygen demand removal efficiency of up to 72 % and more than a twofold enhancement in filtration flux. Moreover, the characteristics of the fouled layer reveal that the B-NiFe2Ox/PS system facilitated the formation of a porous cake layer, maximizing the retention of functional groups on the NF270 membrane surface. Notably, a minor presence of B-NiFe2Ox is uniformly distributed within the cake layer, indicating the in-situ occurrence of weak catalytic oxidation reactions. This study provides an effective and innovative approach utilizing catalytic oxidation for membrane fouling control.

Insight into the co-hydrothermal humification of corn stalk and sewage sludge for enhanced nitrogen-rich humic acid production

Insight into the co-hydrothermal humification of corn stalk and sewage sludge for enhanced nitrogen-rich humic acid production

Hyperthermophilic composting coupled with vermicomposting stimulates transformation of organic matter by altering bacterial community

Hyperthermophilic composting (HTC) has been proven to be an effective strategy to recycle organic wastes, while vermicomposting (VC) has been widely applied to produce humic fertilizer. The combination of HTC with VC (HVC) is expected to integrate the advantages of both. This study showed that HTC pre-fermentation provided plentiful substances such as dissolved organic matter (DOM) for the subsequent VC enriching humic acid (HA). Compared to thermophilic composting (TC), HVC significantly stimulated the degradation of organic matter (OM) and the production of N-rich HA, and incubated higher diversity of bacterial community. SHapley Additive exPlanations (SHAP), correlation network, Mantel test and PLS-LM model were constructed to identify the potential roles of the key bacterial groups contributing to OM transformation. Firmicutes (e.g., Bacillus and Tuberibacillus) dominant in HTC may mineralize and mobilize OM, providing affluent bioavailable nutrients as part of DOM for microbial metabolism and abundant precursors for HA formation in the further VC. Actinobacteriota (e.g., Microbacterium) and Bacteroidota (e.g., Flavobacterium and Parapedobacter) prominent in VC metabolized DOM, mineralized OM and produced HA probably by enhancing the metabolic activity involved in OM degradation and amino acid generation. However, when DOM was exhausted, some members especially Proteobacteria (e.g., Ochrobactrum, Devosia and Cellvibrio) would change their roles from promoter to inhibitor of mineralization and humification. Altering the nutrient bioavailability and the composition of bacterial community can regulate the mineralization, mobilization and humification of OM. Overall, this study provides new insights into the roles of bacteria participating in transforming organic wastes into HA-rich composts.

Thermal Catalytic Production of Potassium Humate Fertilizer from Tobacco Straw and Its Performance in Wheat Hydroponics

Production of artificial humic acid (AHA) from waste biomass will contribute to environmental protection and agricultural productivity. However, there is still a lack of a faster, more efficient and eco-friendly way for sustainable production. In this study, potassium humate was prepared from agricultural waste tobacco straw by thermal catalysis using environmentally friendly Fe2O3 as a catalyst. The yield of potassium humate was successfully increased to 68.77 %. In the present study, using characterization methods such as TG-DTG and UV, it was found that the potassium humate prepared from tobacco straw had lower aromaticity, smaller molecular weight, as well as better solubility and better quality. In addition, the effect of potassium humate fertilizer on wheat biomass was also investigated in this experiment by wheat hydroponics. The results showed that the germination rate of wheat increased by 17 % and the fresh and dry weights increased by 6.94 % and 19.31 %, respectively, with the addition of potassium humate prepared with iron catalyst. This study provides a green and simple technology for the resourceful utilization of tobacco straw to produce high value-added potassium humate, and enriches the source of raw materials for potassium humate, expanding its application in the field of crop growth.

Synergistic effects of Paenibacillus mucilaginosus and Penicillium pimiteouiense on the extraction of humic substances from lignite

Based on the common step of alkaline extraction-acid precipitation, lignite treatment techniques have been developed to improve extraction efficiency and yield of humic acid (HA). This study explored the combination of bacterium Paenibacillus mucilaginosus (P.m) LT1906 and fungus Penicillium pimiteouiense (P.p) LL2205 strains for pre- and post-treatment of lignite collected from eastern Inner Mongol to enhance HA and fulvic acid (FA) yield and plant growth-promoting activity. The lignite was subjected to P.m followed by HNO3 treatment, HNO3 followed by P.p treatment, and a combination of P.m, HNO3 and P.p treatments, then performed by alkaline extraction-acid precipitation technique. The results indicated that P.m pretreatment increased HA yield by 12.47 %, while P.p posttreatment significantly enhanced FA yield by 13.37 %. Combined bacterial and fungal treatments notably improved the total yields of HA and FA by 19.12 %. Structural analysis showed that P.m pretreatment caused the deformation on the lignite surface and the complete lignite oxidation and leaching reactions, thereby increasing the production of HA, yet had no impact on the elemental composition or chemical structure of HA. P.p posttreatment introduced oxygencontaining functional groups and reduced aromatic components through oxidative depolymerization of lignite, leading to increased FA production and HA seed germination-promoting activity.

Lignocellulose hydrothermal artificial humic acid production: Reaction parameters screening and investigation of model/real feedstock

Utilizing relatively mild hydrothermal conversion technique (under optimized conditions, 200 °C, 4 h, 1:10 solid-liquid ratio, 0.5 M NaOH), lignocellulosic biomass can be efficiently transformed into humic acids, thereby significantly enhancing its utilization. Additionally, this approach provides a means for precise manipulation of the composition and properties of the resulting humic acids. In this comprehensive study, lignocellulosic biomass, comprising various attributes like coniferous, broadleaf, and grassy species, as well as model components like cellulose, hemicellulose, and lignin, underwent hydrothermal reactions to produce humic acids. Firstly, a systematic evaluation was conducted to determine the influence of operational parameters on the formation of humic acids. Subsequently, the characteristics of humic acids derived from diverse lignocellulosic biomass sources were analyzed and benchmarked against commercial humic acids. Based on the empirical findings, a mechanistic pathway for the generation of humic acids was figured out. The results indicate that the primary stages in the hydrothermal conversion of lignocellulosic biomass to humic acids involve initial hydrolysis into smaller molecular components, followed by further reactions leading to the formation of humic acids. Notably, the interplay between cellulose, hemicellulose, lignin, and other minor components, such as tannins and pectins, plays a pivotal role in the synthesis of humic acids. The characterization of the derived humic acids revealed several noteworthy distinctions from commercial products. In the infrared spectroscopy (FTIR) and elemental analysis (EA) characterization, the synthetic humic acid has more oxygen functional groups, alkane groups and aromatic structures. In the X-ray photoelectron spectroscopy (XPS), the synthetic humic acid has more diverse forms and proportions of elements. In thermogravimetric analysis (TGA), the synthesized humic acid has higher thermal stability. The synthetic humic acid has a rougher surface microstructure. The synthetic humic acid has higher fluorescence intensity in three-dimensional fluorescence spectrum (3D EEM). Lignocellulose biomass raw materials with high wood quality content can obtain higher humic acid yield, but the interaction of cellulose, hemicellulose, lignin and other group components (such as tannins, pectin, etc.) in the hydrothermal process plays an important role in the generation of humic acid. This research offers valuable insights into the chemically driven production of humic acids and the strategic control of their properties, based on the structural and compositional nuances of the raw materials.

Synergistic enzymatic mechanism of lepidolite leaching enhanced by a mixture of Bacillus mucilaginosus and Bacillus circulans

Numerous studies have demonstrated that the co-leaching of ores by different silicate bacteria significantly improves the performance of bioleaching systems. Nevertheless, the mechanism of different silicate bacteria synergistically or complementarily enhanced the leaching process of lithium-containing silicate remains unclear. This study discussed the leaching impact of the combined presence of two metabolically distinct silicate bacteria on lepidolite, with the aim of comprehending the synergistic effect resulting from the presence of Bacillus mucilaginosus and Bacillus circulans in the leaching process. The results indicated that the polysaccharides and proteins secreted by bacteria-containing functional groups such as -OH and -COOH, which played an important role in the complex decomposition of ores. Organic acids played the role of acid etching and complexation. Bacillus mucilaginosus and Bacillus circulans exhibited low individual leaching efficiency, primarily due to their weak organic acid secretion. Moreover, the prolific polysaccharide production by Bacillus mucilaginosus led to bacterial aggregation, diminishing contact capability with minerals. Bacillus circulans decomposed the excessive polysaccharides produced by Bacillus mucilaginosus through enzymatic hydrolysis in the co-bioleaching process, providing later nutrient supply for both strains. The symbiosis of the two strains enhanced the synthesis and metabolic capabilities of both strains, resulting in increased organic acid secretion. In addition, protein and humic acid production by Bacillus mucilaginosus intensified, collectively enhancing the leaching efficiency. These findings suggested that the primary metabolic products secreted by different bacterial strains in the leaching process differ. The improvement in bioleaching efficiency during co-leaching was attributed to their effective synergistic metabolism. This work contributes to the construction of an efficient engineering microbial community to improve the efficiency of silicate mineral leaching, and reveals the feasibility of microbial co-culture to improve bioleaching.

Enhancing humic acids production from cornstalk under fast hydrothermal conditions: Insights into new pathways of skeleton self-polymerization and branch growth

Hydrochar, a sustainable fertilizer rich in humic substances, is made from lignocellulose through hydrothermal conversion. However, hydrothermal humification (HTH) is challenged by low yields and limited selectivity in the resulting hydrochar. This study proved humic-like acids production can be enhanced under fast non-catalytic conditions (260 ∼ 280 °C, 0 ∼ 1 h). A higher yield (by 14.1 %) and selectivity (by 40.2 %) in hydrochar of humic-like acids than conventional HTH (＜250 °C) were achieved. Meanwhile, decreased lignin derivatives, carbonyl and quinone groups, as well as increased sp2-C structures in the humic-like acids were observed. The synthesized humic-like acids exhibited a lower degree of aromatization and a higher molecular weight than commercial variants. Two pathways of humic-like acids formation of self-polymerization and the development of branched sidechains were hypothesized based on mass mitigation, carbon flow and aqueous phase compositions. This research contributes a novel approach to producing humic-like acids rich hydrochar for environmentally friendly fertilizer production.

Does humic acid foliar application affect growth and nutrient status of water-stressed maize?

Maize (Zea mays L.) is one of the world's most important crops, but its productivity is at high risk as climate change increases the risk of water stress. Therefore, the development of mitigation strategies to combat water stress in agriculture is fundamental to ensure food security. Humic acids are known to have a positive effect on drought tolerance, but data on their efficacy under waterlogging are lacking. This study aimed to elucidate the effect of a new humic acid product, a by-product of Ukrainian bentonite mining, on maize growth and nutrient status under waterlogging. Maize was grown for 9 weeks and three water stress treatments, which were applied for 14 days: waterlogging, alternating waterlogging and drought, and drought. On the day of stress application, the humic acid product (1% v/v) was applied to the leaves. Soil Plant Analysis Development (SPAD) values were recorded during the stress treatments. Plants were harvested after stressing ceased and fresh weight and P and Zn status were analyzed. Drought reduced shoot fresh weight, while it was unaffected under waterlogging. This is in contrast to SPAD readings, which showed a significant decrease over time under submergence, but not under drought. Under alternating stress, although SPAD values declined under waterlogging but stabilized when switched to drought, no growth reduction was apparent. Application of the humic acid product was ineffective in all cases. Although anthocyanin discoloration occurred under waterlogging stress, P deficiency, which is usually the main factor driving anthocyanin formation, was not the reason. Interestingly, Zn concentration decreased under waterlogging but not under the other stresses, which was alleviated by humic acid application. However, no effect of foliar-applied humic acids was observed under alternating and drought stress. It can be concluded that the tested humic acid product has the potential to improve the Zn status of maize under waterlogging.

Investigation of hydrothermal depolymerization of lignite under different conditions by 13C NMR spectroscopy

Efficient depolymerization of lignite under mild conditions is the key to realizing its low carbon conversion and high value utilization. This study focuses on three Chinese lignites: Xilinguole lignite (XL), Xiaolongtan lignite (XLT), and Zhaotong lignite (ZT), investigating the inherent structures effect on their depolymerization processes when subjected to alkali depolymerization (AD) and oxidation depolymerization (OD) under hydrothermal condition. The parent lignites and their depolymerized products were characterized by solid 13C NMR, FTIR, TGA, and elemental analysis. It was found that both AD and OD effectively broke down the macromolecular structure of lignite into humic acid (HA) and small molecular products including water-soluble components, with the highest depolymerization activity observed for ZT followed by XLT and XL, regardless of the method used. Notably, by AD at 80 oC, 91.4 % of ZT was depolymerized, producing 69.4 % of HA as the major product, while higher temperatures were required to efficiently depolymerize XLT and XL by either AD or OD. More than 80% of XLT and XL can be converted by AD at 200 oC, yielding 54.8 % and 52.9 % of HA, respectively. OD at 140 oC resulted in a 57.7 % conversion of XL and an HA yield of 50.2 %. Characterization of the products demonstrated that alkali addition significantly promotes lignite depolymerization by breaking oxygen-containing linkages such as ether and ester bonds, with ether bond hydrolysis occurring predominantly at high temperatures. High-temperature AD of lignite is dominated by the cleavage of oxygen-containing linkages, whereas OD at lower temperatures mainly depolymerizes lignite through oxy-cracking of C−C and C−O weak linkages, reducing carboxyl decomposition to achieve higher HA yields. These findings offer a new perspective on the low-carbon utilization of lignite.

Effect of Humic Amendment on Selected Hydrophysical Properties of Sandy and Clayey Soils

In recent years, products containing humic acids have been increasingly used in agriculture to improve soil parameters. Quantifying their impact on soil quality is, therefore, of key importance. This study seeks to evaluate the impact of the commercial humic acid product (HA) on the hydrophysical parameters of sandy and clayey soils sampled from different sites in Slovakia. Specifically, the study hypothesizes that humic amendment will enhance particle density (ρs), dry bulk density (ρd), porosity (Φ), saturated hydraulic conductivity (Ks), soil water repellency (SWR), and water retention capacity in sandy and clayey soils. The results of the laboratory measurements were analyzed using NCSS statistical software at a statistical significance of p &lt; 0.05. In sandy soil, there was a statistically significant decrease in ρd and Ks and an increase in Φ and a contact angle (CA) after the application of 1 g/100 cm3 HA. At a dose of 6 g/100 cm3 HA, the values of ρs, ρd, and Ks decreased, and the Φ and CA values increased. In clayey soil, the Ks value significantly decreased by −35.5% only after the application of 6 g/100 cm3 HA. The addition of HA increased the full water capacity (FWC) and available water capacity (AWC) of clayey and sandy soils. The positive influence of HA on the studied soil parameters was experimentally confirmed, which can be beneficial, especially for their use in agricultural production.

Humic acid enriched with urea and NPK factory by-products promoted the growth and yield of Saccharum officinarum L.

Nutrient uptake efficiency in sugarcane (Saccharum officinarum L.) must be increased using organic matter to restore soil fertility, resulting in greater productivity. The humic substance is a complex organic material that is excellent for overcoming this challenge. This study aimed to determine the effect of the humic acid enriched by liquid urea by-product (PSUC) and liquid NPK by-product (PSNC) application on the growth and productivity of sugarcane. The experiment was conducted from October 2021 to September 2022 on PT RNI plantation land, Jatitujuh, Majalengka. The research was arranged in a completely randomized (CRD) using two different humic acid product prototypes (PSUC and PSNC) with two evaluation times, a screening and a semi-pilot scale. Solid humic at a dose of 15 Kg ha⁻¹ was applied by mixing it with inorganic fertilizers, while liquid humic at a total dose of 15 L ha⁻¹ was applied by foliar spray technique at 1, 2, and 3 months after planting (MAP). The results showed that applying humic acid PSUC and PSNC enhanced sugarcane shoot growth, segmented stem number, and diameter. In addition, it could consistently promote sugarcane yields on the semi-pilot scale up to 19.18% and 24.26% under humic acid PSUC and PSNC treatments, respectively. Therefore, both in the screening and semi-pilot evaluation, the solid and liquid humic acid PSUC and PSNC applied simultaneously are potential organic materials to enhance sugarcane growth and yield.

Fenton-ultrasound treatment of corn stalks enhances humification during composting by stimulating the inheritance and synthesis of polyphenolic compounds—preliminary evidence from a laboratory trial

The impact of Fenton-ultrasound treatment on the production of polyphenols and humic acid (HA) during corn stalk composting was investigated by analyzing the potential for microbial assimilation of polysaccharides in corn stalks to generate polyphenols using a13C-glucose tracer. The results showed that Fenton-ultrasound treatment promoted the decomposition of lignocellulose and increased the HA content, degree of polymerization (DP), and humification index (HI). The primary factor could be attributed to Fenton-ultrasound treatment-induced enhanced the abundance of lignocellulose-degrading microorganisms, as Firmicutes, Actinobacteria phylum and Aspergillis genus, which serve as the primary driving forces behind polyphenol and HA formation. Additionally, the utilization of a13C isotope tracer revealed that corn stalk polysaccharide decomposition products can be assimilated by microbes and subsequently secrete polyphenolic compounds. This study highlights the potential of microbial activity to generate phenolic compounds, offering a theoretical basis for increasing polyphenol production and promoting HA formation during composting.

Integrating bioprocess and metagenomics studies to enhance humic acid production from rice straw.

Rice straw burning annually (millions of tons) leads to greenhouse gas emissions, and an alternative solution is producing humic acid with high added-value. This study aimed to examine the influence of a microbial consortium and other additives (chicken manure, urea, olive mill waste, zeolite, and biochar) on the composting process of rice straw and the subsequent production of humic acid. Results showed that among the fungal species, Thermoascus aurantiacus exhibited the most prominent impact in expediting maturation and improving compost quality, and Bacillus subtilis was the most abundant bacterial species based on metagenomics analysis. The highest temperature, C/N ratio reduction, and amount of humic acid production (Respectively in lab 61°C, 54.67%, 298 gkg-1 and in pilot level 65°C, 72.11%, 310gkg-1) were related to treatments containing these microorganisms and other additives except urea. Consequently, T. aurantiacus and B. subtilis can be employed on an industrial scale as compost additives to further elevate quality. Functional analysis showed that the bacterial enzymes in the treatments had the highest metabolic activities, including carbohydrate and amino acid metabolism compared to the control. The maximum enzymatic activities were in the thermophilic phase in treatments which were significantly higher than that in the control. The research emphasizes the importance of identifying and incorporating enzymatically active strains that are suitable for temperature conditions, alongside the native strains in decomposing materials. This strategy significantly improves the composting process and yields high-quality humic acid during the thermophilic phase.

Synergistic improvement of humus formation in compost residue by fenton-like and effective microorganism composite agents

Improving the humification of compost through a synergistic approach of biotic and abiotic methods is of great significance. This study employed a composite reagent, comprising Fenton-like agents and effective microorganisms (EM) to improve humification. This composite reagent increased humic-acid production by 37.44 %, reaching 39.82 g kg−1, surpassing the control group. The composite reagent synergistically promoted micromolecular fulvic acid and large humic acid production. Collaborative mechanism suggests that Fenton-like agents contributed to bulk residue decomposition and stimulated the evolution of microbial communities, whereas EMs promoted highly aromatic substance synthesis and adjusted the microbial community structure. Sequencing analysis indicates the Fenton-like agent initiated compost decomposition by Firmicutes, and EM reduced the abundance of Virgibacillus, Lentibacillus, and Alcanivorax. Applied as an organic fertilizer in Brassica chinensis L. plantations, the composite reagent considerably improved growth and photosynthetic pigment content. This composite reagent with biotic and abiotic components provides a learnable method for promoting humification.

Effect of nitrogen retention composite additives Ca(H2PO4)2 and MgSO4 on the degradation of lignocellulose, compost maturation, and fungal communities in compost.

This study investigated the effects of the nitrogen retention composite additives Ca(H2PO4)2 and MgSO4 on lignocellulose degradation, maturation, and fungal communities in composts. The study included control (C, without Ca(H2PO4)2 and MgSO4), 1% Ca(H2PO4)2 + 2% MgSO4 (CaPM1), 1.5% Ca(H2PO4)2 + 3% MgSO4 (CaPM2). The results showed that Ca(H2PO4)2 and MgSO4 enhanced the degradation of total organic carbon (TOC) and promoted the degradation of lignocellulose in compost, with CaPM2 showing the highest TOC and lignocellulose degradation. Changes in the three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM) of dissolved organic matter (DOM) components in compost indicated that the treatment group with the addition of Ca(H2PO4)2 and MgSO4 promoted the production of humic acids (HAs) and increased the degree of compost decomposition, with CaPM2 demonstrating the highest degree of decomposition. The addition of Ca(H2PO4)2 and MgSO4 modified the composition of the fungal community. Ca(H2PO4)2 and MgSO4 increased the relative abundance of Ascomycota, decreased unclassified_Fungi, and Glomeromycota, and activated the fungal genera Thermomyces and Aspergillus, which can degrade lignin and cellulose during the thermophilic stage of composting. Ca(H2PO4)2 and MgSO4 also increased the abundance of Saprotroph, particularly undefined Saprotroph. In conclusion, the addition of Ca(H2PO4)2 and MgSO4 in composting activated fungal communities involved in lignocellulose degradation, promoted the degradation of lignocellulose, and enhanced the maturation degree of compost.

Effect of organic biostimulants on cannabis productivity and soil microbial activity under outdoor conditions

In 2019 and 2020, we investigated the individual and combined effects of two biofertilizers (manure tea and bioinoculant) and one humic acid (HA) product on cannabis biochemical and physiological parameters and soil CO2 evolution under outdoor conditions. Our hypothesis was that HA would increase the microbial activity in the biofertilizers and synergy of both compounds would promote better plant performance and stimulate soil microbial activity. In 2020, the individual and combined application of biofertilizers and HA increased cannabis height, chlorophyll content, photosynthetic efficiency, aboveground biomass, and bucked biomass by 105, 52, 43, 122, and 117%, respectively. Impacts were greater under suboptimal growing conditions caused by planting delay experienced in 2020. In 2019, planting date occurred in-between the most favorable period and chlorophyll content and photosynthetic efficiency were the only parameters influenced by the application of biostimulants. The discrepancies between the two growing seasons reinforce the evidence of other studies that biostimulants efficacy is maximized under stress conditions. This study could not conclusively confirm that the combined use of biofertilizer + HA is a superior practice since affected plant parameters did not differ from application of the compounds singly. Similarly, only one biofertilizer + HA treatment increased soil microbial activity. More research is needed to define optimum rates and combinations of biofertilizer and stimulants for cannabis.