Hemp Biomass Research Articles

Grinding and Fractionation during Distillation Alter Hemp Essential Oil Profile and Its Antimicrobial Activity.

The hypothesis of this study was that we can modify the essential oil (EO) profile of hemp (Cannabis sativa L.) and obtain fractions with differential composition and antimicrobial activity. Therefore, the objective was to evaluate the effects of grinding of hemp biomass before EO extraction and fractionation during distillation on EO profile and antimicrobial activity. The study generated a several EO fractions with a diversity of chemical profile and antimicrobial activity. The highest concentrations of β-pinene and myrcene in the EO can be obtained in the 5–10 min distillation time (DT) of ground material or in the 80–120 min DT of nonground material. High δ-3-carene and limonene EO can be obtained from 0–5 min DT fraction of nonground material. High eucalyptol EO can be sampled either in the 0–5 min DT of the ground material or in the 80–120 min of nonground material. Overall, the highest concentrations of β-caryophyllene, α-(E)-bergamotene, (Z)-β-farnesene, α-humulene, caryophyllenyl alcohol, germacrene D-4-ol, spathulenol, caryophyllene oxide, humulene epoxide 2, β-bisabolol, α-bisabolol, sesquiterpenes, and cannabidiol (CBD) can be obtained when EO is sampled in the 80–120 min DT and the material is nonground. Monoterpenes in the hemp EO can be increased twofold to 85% by grinding the material prior to distillation and collecting the EO in the first 10 min. However, grinding resulted in a slight but significant decrease in the CBD concentration of the EO. CBD-rich oil can be produced by collecting at 120–180 min DT. Different EO fractions had differential antimicrobial activity. The highest antimicrobial activity of EO fraction was found against Staphylococcus aureus subsp. aureus. THC-free EO can be obtained if the EO distillation is limited to 120 min. The results can be utilized by the hemp processing industry and by companies developing new hemp EO-infused products, including perfumery, cosmetics, dietary supplements, food, and pharmaceutical industries.

Phytomanagement of Chromium-Contaminated Soils Using Cannabis sativa (L.)

This study aimed to assess whether hemp (Cannabis sativa L.) behaves as a Cr(III)-tolerant or a hyperaccumulator species and whether it could be a suitable species for the phytomanagement of Cr(III)-contaminated soils. The experiment was conducted in pots under greenhouse conditions comparing two fiber hemp (Fibranova and Carmagnola) and two seed hemp (Futura 75 and Fedora 17) varieties under four different soil Cr levels (24.3, 40.1, 55.8, and 87.4 mg kg−1) supplied with tannery sludge. The Cr level did not significantly influence hemp biomass production or Cr accumulation in the aboveground biomass. Focusing on marketable fractions, Cr uptake was 0.03 ± 0.04 mg plant−1 in the stems of fiber varieties and 0.60 ± 0.17 mg plant−1 in the seeds of seed varieties. The only significant accumulation of Cr content was indeed observed in the root system, where it reached 0.63 mg plant−1 for the fiber varieties and 1.76 mg plant−1 for the seed varieties in the fertilization with 200% N by tannery sludge (T200) treatment. The Cr translocation factor (aboveground-to-belowground biomass) decreased from 2.17 to 0.37, increasing the Cr level applied from 24.3 to 87.4 µg g−1. The maximum Cr concentrations in aboveground biomass fractions (average value of 40.4 mg kg−1) were found in the seeds, regardless of treatment. The low Cr content in the aboveground biomass suggests that hemp can be considered an excluder species, valid as a candidate for Cr-contaminated soils’ phytomanagement.

High Ethanol Concentration (77 g/L) of Industrial Hemp Biomass Achieved Through Optimizing the Relationship between Ethanol Yield/Concentration and Solid Loading.

In this study, the relationships between ethanol yield/concentration and solid loading (6–21%) were investigated to enhance ethanol titer and avoid a random choice of solid loading for simultaneous saccharification and fermentation (SSF). Alkali-pretreated hemp biomass was used for SSF in four scenarios including Case I: 30 filter paper unit (FPU)-cellulase and 140 fungal xylanase unit (FXU)-hemicellulase/g-solid; Case II: 40 FPU-cellulase and 140 FXU-hemicellulase/g-solid; Case III: 30 FPU-cellulase and 140 FXU-hemicellulase/g-solid with 1% Tween80; and Case IV: 30 FPU-cellulase and 140 FXU-hemicellulase/g-solid with particle size reduction (<0.2 mm). Results showed that bioethanol yield and concentration had a negative linear (R2 = 0.76–0.93) and quadratic (R2 = 0.96–0.99) correlation with solid loading (6–21%), respectively. As compared to Case I and previous studies, an enhancement in ethanol yield and concentration through increasing cellulase dose (Case II) and adding Tween 80 (Case III) was overestimated, whereas particle size reduction (Case IV) extended the “solid effect”, evidenced by the highest ethanol concentration (77 g/L) achieved from SSF at the focus point of a quadratic model. An interpretation of the relationship between ethanol yield/concentration and solid loading not only avoids a blind selection of solid loading for SSF but also reduces extra enzymes and water consumption.

Exploring the Biomethane Potential of Different Industrial Hemp (Cannabis sativa L.) Biomass Residues

Industrial hemp stands out as a promising candidate for clean and sustainable biomass-to-bioenergy systems due to its multipurpose, high biomass yield and resource efficiency features. In this study, different hemp biomass residues (HBRs) were evaluated as a potential feedstock for renewable biomethane production through anaerobic digestion (AD). The biochemical methane potential (BMP) of the raw and pretreated fibers, stalks, hurds, leaves and inflorescences was investigated by means of batch anaerobic tests. The highest BMP was obtained with the raw fibers (i.e., 422 ± 20 mL CH4·g VS−1), while hemp hurds (unretted), making up more than half of the whole hemp plant dry weight, showed a lower BMP value of 239 ± 10 mL CH4·g VS−1. The alkali pretreatment of unretted hurds and mechanical grinding of retted hurds effectively enhanced the BMP of both substrates by 15.9%. The mix of leaves and inflorescences and inflorescences alone showed low BMP values (i.e., 118 ± 8 and 26 ± 5 mL CH4·g VS−1, respectively) and a prolonged inhibition of methanogenesis. The latter could be overcome through NaOH pretreatment in the mix of leaves and inflorescences (+28.5% methane production).

Conversion of liquid hot water, acid and alkali pretreated industrial hemp biomasses to bioethanol

In this work, four varieties of hemp biomasses (Helena, SS Beta, Tygra, and Elleta Campana) pretreated with liquid hot water (LHW), H2SO4, and NaOH were investigated for ethanol production. Physicochemical and morphological properties of the pretreated hemp biomass were characterized. LHW achieved high glucan (85–98%) and xylan (67–71%) recoveries. H2SO4 induced significant glucan decomposition (5.9–10.6 g/L) and inhibitor formation (4.5–7.4 g/L of HMF and 2.8–4.5 g/L of furfural) in resulting slurries. Both LHW and H2SO4 pretreatments resulted in low glucose and ethanol yields due to recondensed lignin units. NaOH pretreatment achieved high glucose and ethanol yields due to efficient lignin removal (58.6–75.3%). There was no significant variation in ethanol yield among the four hemp varieties pretreated by NaOH. H2SO4 and NaOH pretreated biomasses showed apparent terraced-field structures and microporous protuberances. Changes in crystallinity indexes and intensities of FTIR peaks were consistent with enhanced cellulose and decreased amorphous hemicellulose.

A Review on the Current State of Knowledge of Growing Conditions, Agronomic Soil Health Practices and Utilities of Hemp in the United States

Hemp (Cannabis sativa L.) is an emerging high-value specialty crop that can be cultivated for either fiber, seed, or cannabidiol (CBD). The demand for hemp and its products has been consistently on the rise in the 21st century. The United States of America (USA) has reintroduced hemp and legalized its production as an agricultural commodity through the 2018 Federal Farm Bill. Although there is a renewed interest in the adoption of hemp due to the emerging market, its production in the United States (US) remains limited partly because of unclear agronomic guidance and fertilization recommendations. This review article provides information on the current agronomic management practices that are available in the literature and identifies the future research needs for cultivating this multipurpose crop to address the growing market demands. Hemp production could be beneficial if managed properly. Hemp fertilizer requirements vary in accordance with the type of hemp grown (seed, fiber, or CBD), soil, environmental conditions and requires a wide range of macro- and micronutrients. Integrating management practices in hemp cultivation intended to build soil health is promising since the hemp cropping system is suitable for crop rotation, cover cropping, and livestock integration through animal waste applications. Hemp also has significant environmental benefits since it has the potential to remediate contaminated soils through phytoremediation, convert high amounts of atmospheric CO2 to biomass through bio-sequestration, and hemp biomass for bioenergy production. This review identifies that most of the agronomic research in the past has been limited to hemp fiber and, to some extent, hemp seed but not CBD hemp. With the increase in the global markets for hemp products, more research needs to be conducted to provide agronomic guidelines for sustainable hemp production.

Biomass of Crotalaria juncea as a function of plant densities in the semiarid region of Northeastern Brazil

An increase in the production per area of sunn hemp (Crotalaria juncea L.) biomass in order to expand its beneficial effects as green manure is an objective for the agronomic management of this species. Three experiments were performed during consecutive years to test the following plant densities per m-2: 10, 20, 30, and 40; 25, 35, 50, and 100; 25, 50, 75, and 100. For each density the spacing between the sowing rows and withinthe rows was equal. The experiments were conducted at Mossoro, RN, Brazil, with a randomized complete block design of four replicates. For each experiment, we determined the shoot dry mass and root dry mass per hectare and the ratio between the values per hectare of shoot dry mass and seed rate. Data were subjected to analysis of variance (F test) and regression analysis. The increasing linear behavior of shoot and root biomass of sunn hemp as a function of plant density establishes a recommendation of 100 plants m-2 with equal spacing in the sowing row and between rows. However, the amount of dry mass produced by each kg of seeds decreased to the density of 90 plants m-2. The amount of biomass produced was limited by the length of the vegetative phase of sunn hemp during day length conditions at Mossoro.

Chemical and Enzymatic Treatment of Hemp Biomass for Bioethanol Production

In this study chemical and enzymatic treatment of hemp biomass were optimized to obtain maximum ethanol production. In the first stage, physical and chemical pretreatment of hemp biomass was carried out. It was found that the Tygra variety is susceptible to alkaline treatment at an optimum concentration of 2% NaOH. Next, the effect of NaOH on the value of reducing sugars and the chemical composition of the solid fraction before and after the treatment was determined. Hemp biomass before and after the chemical treatment was analysed by FTIR spectra and SEM. The effect of enzymatic hydrolysis, i.e., substrate content, temperature, time, pH and dose of enzyme by means of Response Surface Methodology on glucose content was determined. The highest glucose value was observed at 50 °C, in time process between 48 and 72 h, and the dose of enzyme was not less than 20 FPU·g−1. After the optimization of enzymatic hydrolysis two processes of ethanol fermentation from hemp biomass, SHF and SSF, were carried out. In the SHF process a 40% higher concentration of ethanol was obtained (10.51 g/L). In conclusion, hemp biomass was found to be an interesting and promising source to be used for bioethanol production.

Biobased ‘Mid-performance’ composites using losses from the hackling process of long hemp – A feasibility study as part of the development of a biorefinery concept –

The Multihemp biorefinery concept combines processing systems that, starting from harvesting, transform hemp biomass into a spectrum of marketable intermediate and final products. Hackling loss sorted out during production of long hemp was used for the compounding process to produce hemp fibre-reinforced Polylactide (PLA) granules for the injection moulding process. Even though only side stream fibres were used, the overall mechanical properties lie within the range of properties reported for PLA – bast fibre composites cited in the literature or even above. The use of hemp from an earlier harvest at full flowering (harvest 1) significantly increases Young’s modulus values compared to the pure PLA polymer and shows a slightly better reinforcing potential than hemp harvested later at seed maturity (harvest 2). A significant influence of harvest time on the composite properties was found, which is stronger than the variety influence. Based on the presented results, the poly-product MultiHemp system showed a proof of concept for the use of hackling loss for injection moulded composites.

Suitability assessment of different hemp (Cannabis sativa L.) varieties to the cultivation environment

Hemp crop is nowadays spreading in many new areas and then the prediction of crop behavior and performance in different specific environments could be of interest. This study presents a methodology to assess hemp suitability to cropping environments by a combined approach of experimental trials and simulation. The experiment of this study involved six hemp varieties, evaluated for dual-purpose production (seed and stem) during two years of trials in North-East Italy. The results were exploited to develop and calibrate a simulation model able to evaluate hemp crop suitability to the trial environment. Yields obtained for hemp biomass and stems were similar to that of other European experiments, while seed production was shown to be slightly lower. Excessive temperature (daily maximum temperatures over 30 °C) during the grain-filling phase would be one of the main factors affecting seed quality, limiting the seed oil accumulation. Parameters already available in the literature and data obtained from the present experiment were used in the modelling approach to estimate phenological parameters, seed production as affected by water stress, and seed oil content as a function of temperature during the grain-filling period. In order to evaluate the hemp crop suitability to the environment, a scenario analysis using historical meteorological data was performed to predict variability - with different irrigation regimes - of seed yield, seed oil content, maturity date and required seasonal irrigation volume, for each variety in the soil and climatic conditions of the trial site.

Assessment of the Possibility of Using Hemp Biomass (Cannabis Sativa L.) for Energy Purposes: A Case Study

During testing, the possibility of using hemp biomass for energy purposes was assessed. The criteria assessed were the physical and chemical properties of hemp biomass, as well as the combustion process of straw and briquettes made of it in a low-power boiler. The results were made and compared with currently applicable standards. Technical and chemical properties of hemp biomass are comparable with the best plants used for energy purposes. Studies have also shown the susceptibility of hemp biomass compaction. However, large emissions recorded during the combustion of the tested forms of biofuels from hemp straw in light of applicable standards disqualify this fuel for use in grate-type heating devices with air fed under the grate. It would be advisable to carry out research on the total costs of pellet production and their use in heating devices with a retort burner, while taking into account this biofuel’s ashes’ susceptibility of sintering.

The Complex Interactions Between Flowering Behavior and Fiber Quality in Hemp.

Hemp, Cannabis sativa L., is a sustainable multipurpose fiber crop with high nutrient and water use efficiency and with biomass of excellent quality for textile fibers and construction materials. The yield and quality of hemp biomass are largely determined by the genetic background of the hemp cultivar but are also strongly affected by environmental factors, such as temperature and photoperiod. Hemp is a facultative short-day plant, characterized by a strong adaptation to photoperiod and a great influence of environmental factors on important agronomic traits such as “flowering-time” and “sex determination.” This sensitivity of hemp can cause a considerable degree of heterogeneity, leading to unforeseen yield reductions. Fiber quality for instance is influenced by the developmental stage of hemp at harvest. Also, male and female plants differ in stature and produce fibers with different properties and quality. Next to these causes, there is evidence for specific genotypic variation in fiber quality among hemp accessions. Before improved hemp cultivars can be developed, with specific flowering-times and fiber qualities, and adapted to different geographical regions, a better understanding of the molecular mechanisms controlling important phenological traits such as “flowering-time” and “sex determination” in relation to fiber quality in hemp is required. It is well known that genetic factors play a major role in the outcome of both phenological traits, but the major molecular factors involved in this mechanism are not characterized in hemp. Genome sequences and transcriptome data are available but their analysis mainly focused on the cannabinoid pathway for medical purposes. Herein, we review the current knowledge of phenotypic and genetic data available for “flowering-time,” “sex determination,” and “fiber quality” in short-day and dioecious crops, respectively, and compare them with the situation in hemp. A picture emerges for several controlling key genes, for which natural genetic variation may lead to desired flowering behavior, including examples of pleiotropic effects on yield quality and on carbon partitioning. Finally, we discuss the prospects for using this knowledge for the molecular breeding of this sustainable crop via a candidate gene approach.

Influence of raw material properties on energy consumption during briquetting process

Biomass is doubtless a very significant source of renewable energy being worldwide abundant with high energy potential. This paper deals with assessment energy consumption at especially grinding and briquetting processes, which should result in essential economy of energy at solid biofuel production. Various types of raw materials were used at the experiment such as hemp (Cannabis sativa L.) biomass, two species of Miscanthus (Miscanthus sinensis, Miscanthus x gigantheus) and apple wood biomass. These materials were dried, grinded and pressed by piston press having pressing chamber diameter of 65 mm. Materials were grinded into three fractions (4 mm, 8 mm and 12 mm). Material throughput (kg.h-1) and energy consumption (kWh.t-1) were registered. As to results: the highest throughput at both grinding cases as well as briquetting was found at apple wood biomass; however the energy consumption during briquetting of apple wood was relatively high. The worst results concerning throughput and energy consumption (especially at briquetting) were found at hemp biomass. Nevertheless, briquettes made of hemp had the best mechanical durability. Both Miscunthus species (herbaceous biomass) have very similar parameters and showed quite good relation between throughput and energy consumption at the used machines.

Effect of Nitrogen Fertilization on Growth and Yield of Industrial Hemp (Cannabis sativa L.)

Fibre hemp is grown for a multitude of end products derived from its cannabinoids, seed, fibre and wooden core. A key factor that influences the quantity and quality of the production of hemp is nitrogen fertilization. The aim of this study was to determine the response of five well-adapted industrial hemp cultivars to different nitrogen fertilization rates during the 2016 growing season. The experiment was laid out in a split-plot design with two replicates, five main plots (hemp cultivars: ‘Bialobrzeskie’, ‘Tygra’, ‘Felina 32’, ‘Sanhtica 27’, ‘Futura 75’) and sub-plots [fertilization treatments: control (N0), fertilizer 46-0-0 at 120 kg ha-1 (N1), 180 kg ha-1 (N2), 240 kg ha-1 (N3)]. For the computation of height, biomass yield, stem dry weight, length and weight of the inflorescences and mean seed weight, 10 plants were randomly selected in each plot. In general, increasing N fertilization rate positively impacts hemp biomass yield, stem dry weight, plant height, and inflorescence indices. Biomass yield, stem dry weight and inflorescence weight increased by 37.3%, 48.2% and 16%, respectively, with the application of 240 kg N ha-1 when compared with the unfertilized control. Plant height and inflorescence length increased from 1.66 to 1.76 m and from 66.2 to 82.9 cm, respectively, with the application of the higher N rate compared with the control, while there were no significant differences between the fertilization treatments for mean seed weight. The varieties ‘Tygra’ and ‘Futura 75’ showed the highest values for all the measurement characters. Our results indicate that hemp responded well to the addition of N fertilizer.

Hemp Yields and Its Rotation Effects on Wheat under Rainfed Mediterranean Conditions

Core Ideas Rainfed Mediterranean environments might be suitable for double‐purpose hemp production. Hemp is a good predecessor for wheat under rainfed Mediterranean conditions. The beneficial effects of hemp on the subsequent wheat yield appear to last for 2 yr. Monocropping hemp over 2 yr, does not reduce its grain and biomass yields. Hemp (Cannabis sativa L.) has a low impact on the environment requiring few added resources, and has multiple downstream applications. There is little information on hemp biomass, seed yields, and response to NPK fertilization under humid rainfed Mediterranean conditions. Moreover, the effects of hemp on subsequent wheat (Triticum aestivum L.) crops have not been determined. To address these issues, we performed a field study for 6 yr in Catalonia (northeastern Spain). Hemp treatments included: hemp monoculture, unfertilized hemp succeeding wheat, and NPK‐fertilized hemp succeeding wheat. In turn, wheat treatments included: wheat monoculture, first‐, second‐, and third‐year wheat succeeding unfertilized hemp, and first‐, second‐, and third‐year wheat succeeding NPK‐fertilized hemp. The hemp biomass yields (5340–10,090 kg ha−1) were similar to or lower than those achieved in other European regions whereas the hemp seed yields were relatively high (604–1434 kg ha−1). Both the biomass yield and seed yield greatly increased with NPK fertilization. The rotation effects of hemp on the subsequent wheat crops increased the wheat yield by 1368 and 155 kg ha−1 in the first and second years, respectively, but in the third year the yield was similar to the wheat monoculture. The beneficial effects of hemp on wheat therefore appear to last for 2 yr. We conclude that dual‐purpose hemp (harvested for fiber and seed) is an excellent predecessor for wheat, improving the sustainability of cereal‐based cropping systems under humid rainfed Mediterranean conditions.

Immobilization of Cellulase Enzyme on Zinc Ferrite Nanoparticles in Increasing Enzymatic Hydrolysis on Ultrasound-Assisted Alkaline Pretreated Crotalaria Juncea Biomass

Objectives: To synthesize ferrite nano particles; to measure size of the particles by FTIR and XRD studies and enzyme saccharification on ultra sound assisted alkaline pretreated biomass using free and immobilized enzyme. Methods/ Statistical Analysis: In the present work, Zinc ferrite particles were synthesized using co-precipitation method. Cellulase enzymes were immobilized on covalently activated ferrite nanoparticles via glutaraldehyde as a crosslinker. Biochemical characterization of free and immobilized enzyme activity were performed on CMC as a substrate. The efficiency of immobilized enzyme was evaluated based on its binding efficiency on the nanoparticles, thermostability, and reusability. Enzymatic hydrolysis was performed on ultrasound-assisted alkaline pretreated sunn hemp biomass using free and immobilized enzymes. Findings: Around 74% of binding was achieved at 4mg/ml of ferrite loading to enzyme concentration of 20 units. Comparative study on effects of pH and temperature was done on both free and immobilized enzyme and it was observed that the immobilized enzyme has maximum activity at pH 5 and temperature 60˚C. Also, the immobilized enzyme was stable at 60˚C while retaining its activity up to 3 recycles. The immobilized enzyme showed 53% hydrolysis yield on pretreated sunn hemp biomass. Application/Improvements: The research on the interaction between zinc ferrite and cellulase in immobilization and also the recovery of enzymes can determine an efficient approach for bioethanol production in industrial scale. The lab scale can be scaled-up to use at pilot and industrial scales.

Investigations on Physical-mechanical Properties of Effective Thermal Insulation Materials from Fibrous Hemp

Depletion of fossil fuels resources and large amounts of pollutants emitted to the atmosphere enforce searching for alternative renewable resources. One of these resources is fibred hemps. The main components obtainable during the processing of fibred hemp biomass – fibres and shives, they are characterised by low density and porous structure; thereby, they are suitable for the production of thermal insulating composites. The research is based on investigation of two types composites produced from hemp fibres and hemp shives as well as biologically divisible binders. The investigation covers the impact of different amounts of binders and hydrophobizers on physical-mechanical properties.

Enrichment of Cellulosic Waste Hemp (Cannabis sativa) Hurd into Non-Toxic Microfibres.

In this study a largely available lignocellulose feedstock hemp (Cannabis sativa), obtained as an industrial waste, was used for cellulose extraction. The extraction of cellulose microfibres from hemp biomass was conducted by alkaline treatment and an acidification process. The extracted cellulose microfibres were characterised using Fourier-transformed infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). The viability of the study was determined by growing human fibroblasts on the preparation which resulted in being non-toxic; indicating its potential in preparing biological scaffolds. Upon enzymatic hydrolysis of the cellulose microfibre using cellulase from Trichoderma reesei, a maximum of 909 mg/g of reducing sugars were obtained, which endorses its suitability for biofuel production.

Performance of New and Traditional Fiber Hemp (Cannabis sativa L.) Cultivars for Novel Applications: Stem, Bark, and Core Yield and Chemical Composition

Finding a use for all components of hemp is key to improving the overall economics of fiber production from this crop. In this context, the core, a by-product of fiber production, has become increasingly important for new innovative applications. The aim of the present study was to compare traditional and new dioecious and monoecious fiber hemp cultivars in a 2-year field experiment in Central Italy, evaluating the variations on their fiber yield, bark and core production, and their chemical composition. The obtained results underlined the interesting potentiality of the new dioecious genotypes characterized by interesting fiber and nonfiber components which make their utilization appealing in several woven and nonwoven applications. Thanks to the interesting chemical properties recorded for the core fraction, the full use of hemp biomass in a cascade approach can contribute to the total valorization of this versatile fiber crop for a modern biorefinery facility.

Biological and Chemical Characterizations of Allelopathic Potential of Diverse Accessions of the Cover Crop Sunn Hemp

There has been increasing interest in recent years in sunn hemp (Crotalaria juncea), as a leguminous cover crop and green manure, for weed and pest management and improving soil health. Aqueous extracts and ground shoot tissue have previously been demonstrated to be phytotoxic. To further explore its allelopathic potential, bioassays and chemical characterization of water-soluble eluates of sunn hemp were undertaken. Lettuce (Lactuca sativa) radicle growth inhibition was conducted with aqueous eluates from thinly sliced sunn hemp leaves, stems, and seeds, and all three tissues exhibited the inhibitory potential. Fourteen accessions originating from the United States, India, Brazil, South Africa, Pakistan, and Nigeria had water-soluble allelochemicals in leaves, suggesting that allelopathic potential is widely distributed in this species. The highest level of inhibitory potential was found in accession IN-86. Further characterization of IN-86 leaf eluates indicated that the inhibitory compound(s) was/were not soluble in chloroform, but was/were stable when boiled for 15 minutes and resistant to 1 n HCl. Binding and elution from AG-1(OH−) ion-exchange resin also were observed. An analysis of leaf eluates of IN-86 using high-performance liquid chromatography (HPLC) followed by mass spectrometry (MS) showed the presence of a compound with a mass-to-charge ratio of 148, consistent with the spectrum for hydroxynorleucine, a phytotoxic nonprotein amino acid previously reported in seeds of C. juncea. However, its low concentration (&lt;1 μg·mL−1) suggested that other components of the eluate were responsible for the observed allelopathic effect. The results indicate the feasibility for development of weed control strategies using allelochemicals derived from sunn hemp biomass of select genotypes IN-86, NG-71, and BR-20 from India, Nigeria, and Brazil, respectively.