Evidence library
Each finding with its context. The gaps left in view.
Studies of humic and fulvic materials, and the background biology needed to read them, each summarised with its design, its material, its limits and its funding, and placed on the map below. Where the library holds no study, the map says so.
The records
Search the library.
Each record is labelled: a study that tests a humic or fulvic material, or background biology.
Three places to start
Across 81 studies, humic substances raised early plant growth on average, with wide variation.
On average, humic substances raised early plant growth by about a fifth, but the spread was wide: about half of the shoot studies found a gain of less than 5 percent.
Humic acid in incubation water was followed by higher hatch survival in trays, but not in jars.
With the humic acid product in the incubation water, trout eggs in stacked trays hatched better and showed no visible fungus, but eggs in jars did not hatch better.
After an abrupt diet change in twelve dogs, faecal microbes and metabolites shifted within days, then levelled off.
In twelve laboratory dogs switched abruptly to a very different diet, faecal fermentation products and microbes changed within days and were described as settled by the last sample, while stools loosened.
Trout fed a humic and fulvic top‑coating over 140 days grew heavier than controls.
All three inclusion rates produced heavier, longer fish than the control after 140 days, with no difference among rates.
Limitation. Feed intake and feed conversion could not be measured, because fish were fed with a surplus.
Funding. Associated product tested. Co-funded by the product’s manufacturer, which supplied it, and the Ontario Agri-Food Innovation Alliance.
- Study setting
- In the living system
- Study design
- Controlled feeding trial, four diets in triplicate tanks
- Preparation
- A humic and fulvic acid preparation top‑coated onto feed
- Route
- Feed (top‑coated)
- Source
- Chiasson et al., 25 September 2026
In laboratory cell models, a humic acid preparation reduced some inflammatory responses for 24 hours.
Humic acid lowered TNF-α from dog immune cells challenged with endotoxin at 24 hours, but not at 48 hours, and the IL-6 change was only a trend.
Limitation. A cell-culture study using pig intestinal cells and immune cells from one dog; it does not show an effect in a living animal.
Funding. Hungarian public research funding; no conflicts declared.
- Study setting
- In the lab
- Study design
- Laboratory experiment (cell culture)
- Preparation
- Activated leonardite-derived humic acid (66.6 percent total humic acid), sonicated or not
- Route
- Added to cell culture
- Source
- Móritz et al., 7 January 2026
Broilers fed humic substances carried fewer antimicrobial‑resistant E. coli isolates.
Caecal E. coli counts were lower, and the share of multidrug-resistant isolates fell from 43 to 20 percent, in birds fed humic substances.
Limitation. One trial of 40 birds per group, measuring resistance phenotypes only; pen-level clustering was not addressed.
Funding. Slovak public research funding; the additive’s manufacturer is named in the paper.
- Study setting
- In the living system
- Study design
- Controlled feeding trial
- Preparation
- Leonardite-derived humic substances (at least 65 percent humic acids, 5 percent fulvic acids)
- Route
- Feed
- Source
- Pipová et al., 16 April 2025
Prepartum potassium humate was studied at four doses in dairy cows.
Cows fed the two lowest doses before calving had lower NEFA and BHBA than controls; milk yield was highest at the lowest dose and lowest at the highest, the only two groups that differed.
Limitation. One farm with about 15 cows per group; feed intake was measured on subgroups rather than individually.
Funding. Türkiye Coal Enterprises, which also supplied the potassium humate.
- Study setting
- In the living system
- Study design
- Randomised controlled feeding trial
- Preparation
- Potassium humate
- Route
- Feed (concentrate)
- Source
- Uyarlar et al., 2025
A follow-up dairy trial found no change in feed efficiency or milk, with shifts in milk fatty acids.
Feed efficiency, milk yield, components and somatic cell linear score did not differ at six weeks; medium-chain milk fatty acids were higher.
Limitation. Twelve cows per group in two groups started two weeks apart; the authors caution that group creation may explain some effects.
Funding. Manufacturer-supplied report. Funding not stated; the report was supplied by the product’s manufacturer.
- Study setting
- In the living system
- Study design
- Controlled two-group trial
- Preparation
- A humic and fulvic preparation added to drinking water
- Route
- Drinking water
- Source
- University of Guelph, Ridgetown Campus, 2024
Humic acid in incubation water was followed by higher hatch survival in trays, but not in jars.
In stacked trays, fungus was absent and survival to hatch was higher with humic acid; in jars, survival did not differ.
Limitation. The tray and jar results differ, and bacterial communities were described by relative abundance in water, not by load.
Funding. Manufacturer-funded study. Funded by the product’s manufacturer, which also supplied it.
- Study setting
- In the living system
- Study design
- Controlled experiment in two incubation systems
- Preparation
- Humic acid as an aqueous extract of oxidised lignite
- Route
- Incubation water
- Source
- Chiasson, Kirk and Huyben, 19 January 2023
In a university dairy crossover, somatic cell linear score was lower and daily milk showed only a tendency to rise.
Somatic cell linear score was lower with the preparation (3.45 against 4.02); daily milk showed only a tendency to rise, and fat, protein and rumination did not differ.
Limitation. An unpublished report supplied by the manufacturer of the tested preparation, with carry-over effects noted between phases.
Funding. Manufacturer-supplied report. Funding not stated; the report was supplied by the product’s manufacturer.
- Study setting
- In the living system
- Study design
- Crossover trial
- Preparation
- A humic and fulvic preparation added to drinking water
- Route
- Drinking water
- Source
- University of Guelph, Ridgetown Campus, 2023
A fulvic preparation was studied in older laying hens.
Egg weight and shell strength rose slightly and egg breakage fell, while laying rate, feed-to-egg ratio and microbial diversity did not differ.
Limitation. Eight weeks at one dose in one breed; the microbial measures came from six birds per group.
Funding. Provincial and university research funding in Guangdong; no conflicts declared.
- Study setting
- In the living system
- Study design
- Randomised controlled feeding trial
- Preparation
- Fulvic acid from a commercial supplier
- Route
- Feed
- Source
- Xiao et al., 2 September 2022
After an abrupt diet change in twelve dogs, faecal microbes and metabolites shifted within days, then levelled off.
The authors report that faecal metabolites settled within about two days and microbial composition within about six, while stools became looser after both diet changes.
Limitation. Twelve laboratory Beagles followed for 13 days after each change; stability was described from five sampling days rather than tested formally.
Funding. USDA and NomNomNow; three authors are employed by or hold stock options in NomNomNow.
- Study setting
- In the living system
- Study design
- Crossover feeding trial with repeated sampling
- Preparation
- No humic or fulvic material tested; abrupt change from a dry experimental diet to the same diet with added soluble corn fibre, or to a commercial canned diet
- Route
- Feed
- Source
- Lin et al., 1 August 2022
A straw-derived fulvic acid raised greenhouse tomato yield at one soil rate, not at lower or higher rates.
Mixing 2.7 g/kg into pot soil was followed by about 35 percent more fruit than the control; the other soil rates, top dressing and foliar spray did not differ from the control.
Limitation. One season in pots of one soil, with a narrow dose window; mineral results are concentrations, not total uptake, and the material itself carries nitrogen and potassium.
Funding. Manufacturer-funded study. Chinese public funds and the material’s producer, which also employs three of the authors.
- Study setting
- In the living system
- Study design
- Three separate controlled experiments: greenhouse pot culture, seed germination and hydroponic culture
- Preparation
- Fulvic acid made from corn straw, recovered from the residue of bioethanol fermentation (named Zhongliang in the paper)
- Route
- Soil (base and top dressing), foliar spray, germination solution and hydroponic solution, in separate experiments
- Source
- Zhang et al., 11 October 2021
A high-fermented-food diet was followed by higher gut microbiota diversity and lower inflammatory markers; the primary outcome did not change.
The fermented-food arm showed rising microbiota diversity and lower levels of 19 of 93 inflammatory proteins; fibre did not raise diversity, and the primary outcome changed in neither arm.
Limitation. 18 analysed adults per arm, with no control arm and no blinding; diversity and inflammatory markers are measurements, not a health score.
Funding. Donor and institutional funding; several authors hold company interests.
- Study setting
- In the living system
- Study design
- Randomised, open-label comparison of two diets, without a control arm
- Preparation
- No humic or fulvic material tested; high-fibre or high-fermented-food diet
- Route
- Diet (whole foods)
- Source
- Wastyk et al., 12 July 2021
Ponies kept on hay or haylage for years differed more clearly in urinary metabolites than in faecal bacteria.
Urinary metabolite profiles separated in 12 of 13 months, with more hippurate on hay and more ethyl glucoside on haylage, while faecal bacterial diversity did not differ in any month.
Limitation. One group of ten ponies per forage, so forage is confounded with group, pens, paddocks and grass source; forage composition was not reported.
Funding. The Laminitis Trust via Equi Life Ltd, which the corresponding author owns.
- Study setting
- In the living system
- Study design
- Longitudinal study of two forage groups established five years earlier
- Preparation
- No humic or fulvic material tested; long-term feeding of hay or haylage, with summer grazing
- Route
- Feed (forage)
- Source
- Leng et al., 2022 (first online 23 June 2021)
A humic product raised maize yield only on eroded upland soil in drier seasons.
No field-wide yield effect appeared in any of four site-years; significant gains of 7 to 19 percent appeared only on upland soil, mostly in drier seasons.
Limitation. The link to weather rests on correlation and was not tested directly; significance was set at P < 0.10.
Funding. American Colloid Company and USDA-ARS; two authors were employed by Minerals Technologies.
- Study setting
- In the living system
- Study design
- Replicated field experiment (strip plots)
- Preparation
- Micronized leonardite suspension (at least 180 g/kg humic acid and 15 g/kg fulvic acid)
- Route
- Broadcast spray before emergence and at an early vegetative stage
- Source
- Olk et al., 12 May 2021
A high-protein, low-carbohydrate diet shifted faecal bacteria in overweight cats, while no single group changed in lean cats.
In overweight cats, Fusobacteria and Faecalibacterium rose and Megasphaera, Veillonella and Bifidobacterium fell on the high-protein diet; in lean cats no individual taxon differed, and body fat did not change.
Limitation. Thirty-nine colony cats with one faecal sample per phase, on diets designed by the funder's staff; microbial functions were predicted from 16S data, not measured.
Funding. Nestlé Purina PetCare; both authors are Purina employees.
- Study setting
- In the living system
- Study design
- Randomised controlled feeding trial, parallel groups within lean and overweight cats
- Preparation
- No humic or fulvic material tested; two dry diets designed by the funder, differing in protein to carbohydrate ratio
- Route
- Feed
- Source
- Li and Pan, 16 October 2020
Root and foliar applications of a humic acid produced different physiological responses.
Both routes improved shoot and root growth, but foliar application did not reproduce several short-term root responses seen with root application.
Limitation. A short-term hydroponic experiment in one species; the responses concern this preparation and these conditions.
Funding. Cátedra Timac Agro grant; one author is at the Roullier Group’s innovation centre.
- Study setting
- In the lab
- Study design
- Controlled experiment in hydroponic culture
- Preparation
- Sedimentary humic acid extracted from leonardite
- Route
- Root (nutrient solution) and foliar spray, compared
- Source
- De Hita et al., 28 April 2020
Across 81 studies, humic substances raised early plant growth on average, with wide variation.
Pooled estimates showed shoot and root dry weight increases of about 20 percent, yet about half of the shoot studies found a gain of less than 5 percent.
Limitation. Mostly short, early-growth experiments; few statistically rigorous field trials through to crop maturity.
Funding. Funders include coal-sector research bodies.
- Study setting
- Across studies
- Study design
- Meta-analysis with narrative review
- Preparation
- Humic substances from brown coal (including leonardite), peat, soil, composts and manures
- Route
- Root, foliar, soil and combined applications
- Source
- Rose et al., 2014
In a small phase 1 study, oral carbohydrate-derived fulvic acid produced no serious adverse events over exposures of a week or less.
No serious adverse events were reported and blood measures stayed within normal limits apart from one liver-enzyme rise that returned to normal; diarrhoea, sore throat and headache clustered at the top dose, and skin-prick wheals shrank more than on placebo.
Limitation. 30 men enrolled and 21 completed, with no exposure longer than seven days; the efficacy measure was a single skin-prick response.
Funding. No funding source stated; the manufacturer is not named.
- Study setting
- In the living system
- Study design
- Phase 1 dose escalation in two randomised groups, then a double-blind, placebo-controlled crossover
- Preparation
- Carbohydrate-derived fulvic acid, 3.8 percent oral preparation
- Route
- Oral
- Source
- Gandy et al., 17 February 2012
A small trial of a topical fulvic acid cream for eczema reported a better investigator rating than placebo.
The investigator's global rating favoured the fulvic acid cream, while severity and redness improved within both the treated and placebo groups.
Limitation. A small exploratory trial of 36 people, applied to the skin; it says nothing about taking fulvic acid by mouth.
Funding. No funding source stated; no conflicts reported.
- Study setting
- In the living system
- Study design
- Randomised, double-blind, placebo-controlled trial
- Preparation
- Carbohydrate-derived fulvic acid, 3.5 percent in an emollient
- Route
- Topical (applied to the skin)
- Source
- Gandy, Snyman and van Rensburg, 8 September 2011
No records match these filters.
An empty result means this collection holds no matching record yet, not that no such study exists. Try a broader search or clear a filter.
A curated collection, not an exhaustive or systematic review. Inclusion does not imply endorsement. This library holds no study of a humic or fulvic material in horses. The evidence map below shows that gap and the others, so researchers can see where work is needed.
The evidence mapWhat this collection holds, and where it holds nothing yet.
- A humic or fulvic material was tested.
- The biology of the system, with no material tested.
- None in this library yet.
None in this library yetRoot and foliar applications of a humic acid produced different physiological responses.A humic product raised maize yield only on eroded upland soil in drier seasons.A straw-derived fulvic acid raised greenhouse tomato yield at one soil rate, not at lower or higher rates.Across 81 studies, humic substances raised early plant growth on average, with wide variation.
By species belowBy species belowBy species belowBy species below
None in this library yetNone in this library yetHumic acid in incubation water was followed by higher hatch survival in trays, but not in jars.Trout fed a humic and fulvic top‑coating over 140 days grew heavier than controls.None in this library yet
A high-protein, low-carbohydrate diet shifted faecal bacteria in overweight cats, while no single group changed in lean cats.After an abrupt diet change in twelve dogs, faecal microbes and metabolites shifted within days, then levelled off.In laboratory cell models, a humic acid preparation reduced some inflammatory responses for 24 hours.None in this library yetNone in this library yet
Ponies kept on hay or haylage for years differed more clearly in urinary metabolites than in faecal bacteria.None in this library yetNone in this library yetNone in this library yet
A high-fermented-food diet was followed by higher gut microbiota diversity and lower inflammatory markers; the primary outcome did not change.None in this library yetA small trial of a topical fulvic acid cream for eczema reported a better investigator rating than placebo.In a small phase 1 study, oral carbohydrate-derived fulvic acid produced no serious adverse events over exposures of a week or less.None in this library yetThis map describes the current collection, not the entire literature. Every record, by living system and by where the material met the biology; select a system to filter the list. An empty cell means this collection holds no record there yet.
Know a study that belongs in an empty cell? Suggest a source.
Reading the evidence
The finding and its context belong together.
A result becomes more useful when we understand how it was obtained and where it applies. Our summaries consider the design, material, population, measurements and limits of each source.
A useful study can answer a narrow question. A field observation can identify a question worth investigating. Neither needs to be presented as more than it is.
Both routes improved shoot and root growth, but foliar application did not reproduce several short-term root responses seen with root application.
a The design
Was there a comparison group? How were participants or experimental units assigned? Which alternative explanations remain?
b, d The material
What preparation was tested? How was it characterised, and does it match the application being discussed?
c The system
Which species, life stage or environment was studied? How closely does that setting match the reader’s question?
centre The measurement
What was measured directly? What was inferred? Were changes statistically supported, and how large were they?
e, f The interpretation
What does the result support? What remains uncertain, and what additional work would help answer it?
Editorial standards
Traceable sources. Clear distinctions. Visible updates.
Traceable sources
Source identification
We identify the original source and provide a direct link where available. Summaries distinguish source findings from Carbon Biome Project interpretation.
Transparent relationships
We identify known project, brand and funding relationships relevant to the record.
Clear distinctions
Balanced reporting
We include relevant limitations, mixed findings and results that did not show a statistically supported difference.
Preparation-specific interpretation
We do not assume that findings transfer between materials, products, species or application routes.
Visible updates
Accurate review status
We name reviewers and describe their contribution only when a review has occurred. Editorial preparation is distinct from external scientific review.
Corrections and updates
We revise records when errors, source corrections or material new information are identified. Significant changes are noted on the record.
Study exposure
0.005 mg/L
0.005 mL of the product per litre (5 mg/L in the published correction)
Correction notice · The record · Manufacturer-funded study
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